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Tullius MV, Bowen RA, Back PS, Masleša-Galić S, Nava S, Horwitz MA. LVS Δ capB-vectored multiantigenic melioidosis vaccines protect against lethal respiratory Burkholderia pseudomallei challenge in highly sensitive BALB/c mice. mBio 2024; 15:e0018624. [PMID: 38511933 PMCID: PMC11005352 DOI: 10.1128/mbio.00186-24] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2024] [Accepted: 02/05/2024] [Indexed: 03/22/2024] Open
Abstract
Melioidosis, caused by the intracellular bacterial pathogen and Tier 1 select agent Burkholderia pseudomallei (Bp), is a highly fatal disease endemic in tropical areas. No licensed vaccine against melioidosis exists. In preclinical vaccine studies, demonstrating protection against respiratory infection in the highly sensitive BALB/c mouse has been especially challenging. To address this challenge, we have used a safe yet potent live attenuated platform vector, LVS ΔcapB, previously used successfully to develop vaccines against the Tier 1 select agents of tularemia, anthrax, and plague, to develop a melioidosis vaccine. We have engineered melioidosis vaccines (rLVS ΔcapB/Bp) expressing multiple immunoprotective Bp antigens among type VI secretion system proteins Hcp1, Hcp2, and Hcp6, and membrane protein LolC. Administered intradermally, rLVS ΔcapB/Bp vaccines strongly protect highly sensitive BALB/c mice against lethal respiratory Bp challenge, but protection is overwhelmed at very high challenge doses. In contrast, administered intranasally, rLVS ΔcapB/Bp vaccines remain strongly protective against even very high challenge doses. Under some conditions, the LVS ΔcapB vector itself provides significant protection against Bp challenge, and consistent with this, both the vector and vaccines induce humoral immune responses to Bp antigens. Three-antigen vaccines expressing Hcp6-Hcp1-Hcp2 or Hcp6-Hcp1-LolC are among the most potent and provide long-term protection and protection even with a single intranasal immunization. Protection via the intranasal route was either comparable to or statistically significantly better than the single-deletional Bp mutant Bp82, which served as a positive control. Thus, rLVS ΔcapB/Bp vaccines are exceptionally promising safe and potent melioidosis vaccines. IMPORTANCE Melioidosis, a major neglected disease caused by the intracellular bacterial pathogen Burkholderia pseudomallei, is endemic in many tropical areas of the world and causes an estimated 165,000 cases and 89,000 deaths in humans annually. Moreover, B. pseudomallei is categorized as a Tier 1 select agent of bioterrorism, largely because inhalation of low doses can cause rapidly fatal pneumonia. No licensed vaccine is available to prevent melioidosis. Here, we describe a safe and potent melioidosis vaccine that protects against lethal respiratory challenge with B. pseudomallei in a highly sensitive small animal model-even a single immunization is highly protective, and the vaccine gives long-term protection. The vaccine utilizes a highly attenuated replicating intracellular bacterium as a vector to express multiple key proteins of B. pseudomallei; this vector platform has previously been used successfully to develop potent vaccines against other Tier 1 select agent diseases including tularemia, anthrax, and plague.
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Affiliation(s)
- Michael V. Tullius
- Division of Infectious Diseases, Department of Medicine, Center for Health Sciences, School of Medicine, University of California, Los Angeles, California, USA
| | - Richard A. Bowen
- Department of Biomedical Sciences, Colorado State University, Fort Collins, Colorado, USA
| | - Peter S. Back
- Division of Infectious Diseases, Department of Medicine, Center for Health Sciences, School of Medicine, University of California, Los Angeles, California, USA
| | - Saša Masleša-Galić
- Division of Infectious Diseases, Department of Medicine, Center for Health Sciences, School of Medicine, University of California, Los Angeles, California, USA
| | - Susana Nava
- Division of Infectious Diseases, Department of Medicine, Center for Health Sciences, School of Medicine, University of California, Los Angeles, California, USA
| | - Marcus A. Horwitz
- Division of Infectious Diseases, Department of Medicine, Center for Health Sciences, School of Medicine, University of California, Los Angeles, California, USA
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Chaiden C, Jaresitthikunchai J, Phaonakrop N, Roytrakul S, Kerdsin A, Nuanualsuwan S. Unlocking the Secrets of Streptococcus suis: A peptidomics comparison of virulent and non-virulent serotypes 2, 14, 18, and 19. PLoS One 2023; 18:e0287639. [PMID: 37384746 PMCID: PMC10310009 DOI: 10.1371/journal.pone.0287639] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2023] [Accepted: 06/09/2023] [Indexed: 07/01/2023] Open
Abstract
Streptococcus suis (S. suis) is an important bacterial pathogen, that causes serious infections in humans and pigs. Although numerous virulence factors have been proposed, their particular role in pathogenesis is still inconclusive. The current study explored putative peptides responsible for the virulence of S. suis serotype 2 (SS2). Thus, the peptidome of highly virulent SS2, less prevalent SS14, and rarely reported serotypes SS18 and SS19 were comparatively analyzed using a high-performance liquid chromatography-mass spectrometry method (LC-MS/MS). Six serotype-specific peptides, 2,3,4,5-tetrahydropyridine-2,6-dicarboxylate N-acetyltransferase (DapH), alanine racemase (Alr), CCA-adding enzyme (CCA), peptide chain release factor 3 (RF3), ATP synthase subunit delta (F0F1-ATPases) and aspartate carbamoyltransferase (ATCase), were expressed moderately to highly only in the SS2 peptidome with p-values of less than 0.05. Some of these proteins are responsible for bacterial cellular stability; especially, Alr was highly expressed in the SS2 peptidome and is associated with peptidoglycan biosynthesis and bacterial cell wall formation. This study indicated that these serotype-specific peptides, which were significantly expressed by virulent SS2, could serve as putative virulence factors to promote its competitiveness with other coexistences in a particular condition. Further in vivo studies of these peptides should be performed to confirm the virulence roles of these identified peptides.
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Affiliation(s)
- Chadaporn Chaiden
- Faculty of Veterinary Sciences, Department of Veterinary Public Health, Chulalongkorn University, Bangkok, Thailand
- Faculty of Veterinary Science, Department of Veterinary Public Health, Center of Excellence for Food and Water Risk Analysis (FAWRA), Chulalongkorn University, Bangkok, Thailand
| | - Janthima Jaresitthikunchai
- Functional Proteomics Technology Laboratory, Functional Ingredients and Food Innovation Research Group, National Center for Genetic Engineering and Biotechnology, National Science and Technology for Development Agency, Pathum Thani, Thailand
| | - Narumon Phaonakrop
- Functional Proteomics Technology Laboratory, Functional Ingredients and Food Innovation Research Group, National Center for Genetic Engineering and Biotechnology, National Science and Technology for Development Agency, Pathum Thani, Thailand
| | - Sittiruk Roytrakul
- Functional Proteomics Technology Laboratory, Functional Ingredients and Food Innovation Research Group, National Center for Genetic Engineering and Biotechnology, National Science and Technology for Development Agency, Pathum Thani, Thailand
| | - Anusak Kerdsin
- Faculty of Public Health, Kasetsart University Chalermphrakiat Sakon Nakhon Province Campus, Sakon Nakhon, Thailand
| | - Suphachai Nuanualsuwan
- Faculty of Veterinary Sciences, Department of Veterinary Public Health, Chulalongkorn University, Bangkok, Thailand
- Faculty of Veterinary Science, Department of Veterinary Public Health, Center of Excellence for Food and Water Risk Analysis (FAWRA), Chulalongkorn University, Bangkok, Thailand
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Hall CM, Somprasong N, Hagen JP, Nottingham R, Sahl JW, Webb JR, Mayo M, Currie BJ, Podin Y, Wagner DM, Keim P, Schweizer HP. Exploring Cefiderocol Resistance Mechanisms in Burkholderia pseudomallei. Antimicrob Agents Chemother 2023; 67:e0017123. [PMID: 37133377 PMCID: PMC10269091 DOI: 10.1128/aac.00171-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2023] [Accepted: 04/04/2023] [Indexed: 05/04/2023] Open
Abstract
Cefiderocol is a siderophore cephalosporin designed mainly for treatment of infections caused by β-lactam and multidrug-resistant Gram-negative bacteria. Burkholderia pseudomallei clinical isolates are usually highly cefiderocol susceptible, with in vitro resistance found in a few isolates. Resistance in clinical B. pseudomallei isolates from Australia is caused by a hitherto uncharacterized mechanism. We show that, like in other Gram-negatives, the PiuA outer membrane receptor plays a major role in cefiderocol nonsusceptibility in isolates from Malaysia.
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Affiliation(s)
- Carina M. Hall
- The Pathogen and Microbiome Institute, Northern Arizona University, Flagstaff, Arizona, USA
| | - Nawarat Somprasong
- The Pathogen and Microbiome Institute, Northern Arizona University, Flagstaff, Arizona, USA
| | - Johannah P. Hagen
- The Pathogen and Microbiome Institute, Northern Arizona University, Flagstaff, Arizona, USA
| | - Roxanne Nottingham
- The Pathogen and Microbiome Institute, Northern Arizona University, Flagstaff, Arizona, USA
| | - Jason W. Sahl
- The Pathogen and Microbiome Institute, Northern Arizona University, Flagstaff, Arizona, USA
- Department of Biological Sciences, Northern Arizona University, Flagstaff, Arizona, USA
| | - Jessica R. Webb
- Global and Tropical Health Division, Menzies School of Health Research, Charles Darwin University, Darwin, Northern Territory, Australia
- Department of Microbiology and Immunology at the Peter Doherty Institute for Infection and Immunity, University of Melbourne, Melbourne, Australia
| | - Mark Mayo
- Global and Tropical Health Division, Menzies School of Health Research, Charles Darwin University, Darwin, Northern Territory, Australia
| | - Bart J. Currie
- Global and Tropical Health Division, Menzies School of Health Research, Charles Darwin University, Darwin, Northern Territory, Australia
| | - Yuwana Podin
- Institute of Health and Community Medicine, Universiti Malaysia Sarawak, Sarawak, Malaysia
| | - David M. Wagner
- The Pathogen and Microbiome Institute, Northern Arizona University, Flagstaff, Arizona, USA
- Department of Biological Sciences, Northern Arizona University, Flagstaff, Arizona, USA
| | - Paul Keim
- The Pathogen and Microbiome Institute, Northern Arizona University, Flagstaff, Arizona, USA
- Department of Biological Sciences, Northern Arizona University, Flagstaff, Arizona, USA
| | - Herbert P. Schweizer
- The Pathogen and Microbiome Institute, Northern Arizona University, Flagstaff, Arizona, USA
- Department of Biological Sciences, Northern Arizona University, Flagstaff, Arizona, USA
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4
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Somprasong N, Hagen JP, Sahl JW, Webb JR, Hall CM, Currie BJ, Wagner DM, Keim P, Schweizer HP. A conserved active site PenA β-lactamase Ambler motif specific for Burkholderia pseudomallei/B. mallei is likely responsible for intrinsic amoxicillin-clavulanic acid sensitivity and facilitates a simple diagnostic PCR assay for melioidosis. Int J Antimicrob Agents 2023; 61:106714. [PMID: 36640845 DOI: 10.1016/j.ijantimicag.2023.106714] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2022] [Revised: 11/23/2022] [Accepted: 12/31/2022] [Indexed: 01/13/2023]
Abstract
Burkholderia pseudomallei is a soil- and water-dwelling Gram-negative bacterium that causes melioidosis in humans and animals. Amoxicillin-clavulanic acid (AMC) susceptibility has been hailed as an integral part of the screening algorithm for identification of B. pseudomallei, but the molecular basis for the inherent AMC susceptibility of this bacterium remains undefined. This study showed that B. pseudomallei (and the closely-related B. mallei) wild-type strains are the only Burkholderia spp. that contain a 70STSK73 PenA Ambler motif. This motif was present in >99.5% of 1820 analysed B. pseudomallei strains and 100% of 83 analysed B. mallei strains, and is proposed as the likely cause for their inherent AMC sensitivity. The authors developed a polymerase chain reaction (PCR) assay that specifically amplifies the penA70ST(S/F)K73-containing region from B. pseudomallei and B. mallei, but not from the remaining B. pseudomallei complex species or the 70STFK73 region from the closely-related penB of B. cepacia complex species. The abundance and purity of the 193-bp PCR fragment from putative B. pseudomallei isolates from clinical and environmental samples is likely sufficient for reliable confirmation of the presence of B. pseudomallei. The PCR assay is designed to be especially suited for use in resource-constrained areas. While not further explored in this study, the assay may allow diagnosis of putative B. mallei in culture isolates from animal and human samples.
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Affiliation(s)
- Nawarat Somprasong
- The Pathogen and Microbiome Institute, Northern Arizona University, 1395 S Knoles Dr. Flagstaff, AZ 86001-4073, USA
| | - Johannah P Hagen
- The Pathogen and Microbiome Institute, Northern Arizona University, 1395 S Knoles Dr. Flagstaff, AZ 86001-4073, USA
| | - Jason W Sahl
- The Pathogen and Microbiome Institute, Northern Arizona University, 1395 S Knoles Dr. Flagstaff, AZ 86001-4073, USA; Department of Biological Sciences, Northern Arizona University, Flagstaff, Arizona, USA
| | - Jessica R Webb
- Global and Tropical Health Division, Menzies School of Health Research, Charles Darwin University, Darwin, Northern Territory, Australia; Department of Microbiology and Immunology, Peter Doherty Institute for Infection and Immunity, The University of Melbourne, Melbourne, Australia
| | - Carina M Hall
- The Pathogen and Microbiome Institute, Northern Arizona University, 1395 S Knoles Dr. Flagstaff, AZ 86001-4073, USA
| | - Bart J Currie
- Global and Tropical Health Division, Menzies School of Health Research, Charles Darwin University, Darwin, Northern Territory, Australia; Department of Infectious Diseases and Northern Territory Medical Programme, Royal Darwin Hospital, Darwin, Northern Territory, Australia
| | - David M Wagner
- The Pathogen and Microbiome Institute, Northern Arizona University, 1395 S Knoles Dr. Flagstaff, AZ 86001-4073, USA; Department of Biological Sciences, Northern Arizona University, Flagstaff, Arizona, USA
| | - Paul Keim
- The Pathogen and Microbiome Institute, Northern Arizona University, 1395 S Knoles Dr. Flagstaff, AZ 86001-4073, USA; Department of Biological Sciences, Northern Arizona University, Flagstaff, Arizona, USA
| | - Herbert P Schweizer
- The Pathogen and Microbiome Institute, Northern Arizona University, 1395 S Knoles Dr. Flagstaff, AZ 86001-4073, USA; Department of Biological Sciences, Northern Arizona University, Flagstaff, Arizona, USA.
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Sun Z, Heacock-Kang Y, McMillan IA, Cabanas D, Zarzycki-Siek J, Hoang TT. A virulence activator of a surface attachment protein in Burkholderia pseudomallei acts as a global regulator of other membrane-associated virulence factors. Front Microbiol 2023; 13:1063287. [PMID: 36726566 PMCID: PMC9884982 DOI: 10.3389/fmicb.2022.1063287] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2022] [Accepted: 12/30/2022] [Indexed: 01/19/2023] Open
Abstract
Burkholderia pseudomallei (Bp), causing a highly fatal disease called melioidosis, is a facultative intracellular pathogen that attaches and invades a variety of cell types. We previously identified BP1026B_I0091 as a surface attachment protein (Sap1) and an essential virulence factor, contributing to Bp pathogenesis in vitro and in vivo. The expression of sap1 is regulated at different stages of Bp intracellular lifecycle by unidentified regulator(s). Here, we identified SapR (BP1026B_II1046) as a transcriptional regulator that activates sap1, using a high-throughput transposon mutagenesis screen in combination with Tn-Seq. Consistent with phenotypes of the Δsap1 mutant, the ΔsapR activator mutant exhibited a significant reduction in Bp attachment to the host cell, leading to subsequent decreased intracellular replication. RNA-Seq analysis further revealed that SapR regulates sap1. The regulation of sap1 by SapR was confirmed quantitatively by qRT-PCR, which also validated the RNA-Seq data. SapR globally regulates genes associated with the bacterial membrane in response to diverse environments, and some of the genes regulated by SapR are virulence factors that are required for Bp intracellular infection (e.g., type III and type VI secretion systems). This study has identified the complex SapR regulatory network and its importance as an activator of an essential Sap1 attachment factor.
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Affiliation(s)
- Zhenxin Sun
- School of Life Sciences, University of Hawai'i at Mānoa, Honolulu, HI, United States
| | - Yun Heacock-Kang
- School of Life Sciences, University of Hawai'i at Mānoa, Honolulu, HI, United States
| | - Ian A McMillan
- School of Life Sciences, University of Hawai'i at Mānoa, Honolulu, HI, United States
| | - Darlene Cabanas
- School of Life Sciences, University of Hawai'i at Mānoa, Honolulu, HI, United States
| | - Jan Zarzycki-Siek
- School of Life Sciences, University of Hawai'i at Mānoa, Honolulu, HI, United States
| | - Tung T Hoang
- School of Life Sciences, University of Hawai'i at Mānoa, Honolulu, HI, United States
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6
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Burkholderia pseudomallei JW270 Is Lethal in the Madagascar Hissing Cockroach Infection Model and Can Be Utilized at Biosafety Level 2 to Identify Putative Virulence Factors. Infect Immun 2022; 90:e0015922. [PMID: 35862734 PMCID: PMC9387215 DOI: 10.1128/iai.00159-22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
Burkholderia pseudomallei, the causative agent of melioidosis, is classified by the CDC as a tier 1 select agent, and work involving it must be performed in a biosafety level 3 (BSL-3) laboratory. Three BSL-2 surrogate strains derived from B. pseudomallei 1026b, a virulent clinical isolate, have been removed from the CDC select agent list. These strains, Bp82, B0011, and JW270, are highly attenuated in rodent models of melioidosis and cannot be utilized to identify virulence determinants because of their high 50% lethal dose (LD50). We previously demonstrated that the Madagascar hissing cockroach (MHC) is a tractable surrogate host to study the innate immune response against Burkholderia. In this study, we found that JW270 maintains its virulence in MHCs. This surprising result indicates that it may be possible to identify potential virulence genes in JW270 by using MHCs at BSL-2. We tested this hypothesis by constructing JW270 mutations in genes that are required (hcp1) or dispensable (hcp2) for B. pseudomallei virulence in rodents. JW270 Δhcp1 was avirulent in MHCs and JW270 Δhcp2 was virulent, suggesting that MHCs can be used at BSL-2 for the discovery of important virulence factors. JW270 ΔBPSS2185, a strain harboring a mutation in a type IV pilin locus (TFP8) required for full virulence in BALB/c mice, was also found to be attenuated in MHCs. Finally, we demonstrate that the hmqA-G locus, which encodes the production of a family of secondary metabolites called 4-hydroxy-3-methyl-2-alkylquinolines, is important for JW270 virulence in MHCs and may represent a novel virulence determinant.
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Development of Melioidosis Subunit Vaccines Using an Enzymatically Inactive Burkholderia pseudomallei AhpC. Infect Immun 2022; 90:e0022222. [PMID: 35862715 PMCID: PMC9387246 DOI: 10.1128/iai.00222-22] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
Burkholderia pseudomallei, the causative agent of melioidosis, is a facultative intracellular, Gram-negative pathogen that is highly infectious via the respiratory route and can cause severe, debilitating, and often fatal diseases in humans and animals. At present, no licensed vaccines for immunization against this CDC Tier 1 select agent exist. Studies in our lab have previously demonstrated that subunit vaccine formulations consisting of a B. pseudomallei capsular polysaccharide (CPS)-based glycoconjugate (CPS-CRM197) combined with hemolysin-coregulated protein (Hcp1) provided C57BL/6 mice with high-level protection against an acute inhalational challenge of B. pseudomallei. In this study, we evaluated the immunogenicity and protective capacity of B. pseudomallei alkyl hydroperoxide reductase subunit C (AhpC) in combination with CPS-CRM197. AhpC is a peroxiredoxin involved in oxidative stress reduction and is a potential protective antigen. To facilitate our studies and maximize safety in animals, recombinant B. pseudomallei AhpC harboring an active site mutation (AhpCC57G) was expressed in Escherichia coli and purified using tandem nickel-cobalt affinity chromatography. Immunization of C57BL/6 mice with CPS-CRM197 combined with AhpCC57G stimulated high-titer IgG responses against the CPS component of the glycoconjugate as well as stimulated high-titer IgG and robust interferon gamma (IFN-γ)-, interleukin-5 (IL-5)-, and IL-17-secreting T cell responses against AhpCC57G. When challenged via an inhalational route with a high dose (~27 50% lethal doses [LD50s]) of B. pseudomallei, 70% of the immunized mice survived 35 days postchallenge. Collectively, our findings demonstrate that AhpCC57G is a potent activator of cellular and humoral immune responses and may be a promising candidate to include in future melioidosis subunit vaccines.
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Borlee GI, Mangalea MR, Martin KH, Plumley BA, Golon SJ, Borlee BR. Disruption of c-di-GMP Signaling Networks Unlocks Cryptic Expression of Secondary Metabolites during Biofilm Growth in Burkholderia pseudomallei. Appl Environ Microbiol 2022; 88:e0243121. [PMID: 35357191 PMCID: PMC9040570 DOI: 10.1128/aem.02431-21] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2021] [Accepted: 03/04/2022] [Indexed: 11/20/2022] Open
Abstract
The regulation and production of secondary metabolites during biofilm growth of Burkholderia spp. is not well understood. To learn more about the crucial role and regulatory control of cryptic molecules produced during biofilm growth, we disrupted c-di-GMP signaling in Burkholderia pseudomallei, a soilborne bacterial saprophyte and the etiologic agent of melioidosis. Our approach to these studies combined transcriptional profiling with genetic deletions that targeted key c-di-GMP regulatory components to characterize responses to changes in temperature. Mutational analyses and conditional expression studies of c-di-GMP genes demonstrates their contribution to phenotypes such as biofilm formation, colony morphology, motility, and expression of secondary metabolite biosynthesis when grown as a biofilm at different temperatures. RNA-seq analysis was performed at various temperatures in a ΔII2523 mutant background that is responsive to temperature alterations resulting in hypobiofilm- and hyperbiofilm-forming phenotypes. Differential regulation of genes was observed for polysaccharide biosynthesis, secretion systems, and nonribosomal peptide and polyketide synthase (NRPS/PKS) clusters in response to temperature changes. Deletion mutations of biosynthetic gene clusters (BGCs) 2, 11, 14 (syrbactin), and 15 (malleipeptin) in parental and ΔII2523 backgrounds also reveal the contribution of these BGCs to biofilm formation and colony morphology in addition to inhibition of Bacillus subtilis and Rhizoctonia solani. Our findings suggest that II2523 impacts the regulation of genes that contribute to biofilm formation and competition. Characterization of cryptic BGCs under different environmental conditions will allow for a better understanding of the role of secondary metabolites in the context of biofilm formation and microbe-microbe interactions. IMPORTANCE Burkholderia pseudomallei is a saprophytic bacterium residing in the environment that switches to a pathogenic lifestyle during infection of a wide range of hosts. The environmental cues that serve as the stimulus to trigger this change are largely unknown. However, it is well established that the cellular level of c-di-GMP, a secondary signal messenger, controls the switch from growth as planktonic cells to growth as a biofilm. Disrupting the signaling mediated by c-di-GMP allows for a better understanding of the regulation and the contribution of the surface associated and secreted molecules that contribute to the various lifestyles of this organism. The genome of B. pseudomallei also encodes cryptic biosynthetic gene clusters predicted to encode small molecules that potentially contribute to growth as a biofilm, adaptation, and interactions with other organisms. A better understanding of the regulation of these molecules is crucial to understanding how this versatile pathogen alters its lifestyle.
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Affiliation(s)
- Grace I. Borlee
- Department of Microbiology, Immunology, and Pathology, Colorado State University, Fort Collins, Colorado, USA
| | - Mihnea R. Mangalea
- Department of Microbiology, Immunology, and Pathology, Colorado State University, Fort Collins, Colorado, USA
| | - Kevin H. Martin
- Department of Microbiology, Immunology, and Pathology, Colorado State University, Fort Collins, Colorado, USA
| | - Brooke A. Plumley
- Department of Microbiology, Immunology, and Pathology, Colorado State University, Fort Collins, Colorado, USA
| | - Samuel J. Golon
- Department of Microbiology, Immunology, and Pathology, Colorado State University, Fort Collins, Colorado, USA
| | - Bradley R. Borlee
- Department of Microbiology, Immunology, and Pathology, Colorado State University, Fort Collins, Colorado, USA
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Mangalea MR, Borlee BR. The NarX-NarL two-component system regulates biofilm formation, natural product biosynthesis, and host-associated survival in Burkholderia pseudomallei. Sci Rep 2022; 12:203. [PMID: 34997073 PMCID: PMC8742066 DOI: 10.1038/s41598-021-04053-6] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2021] [Accepted: 12/14/2021] [Indexed: 01/10/2023] Open
Abstract
Burkholderia pseudomallei is a saprophytic bacterium endemic throughout the tropics causing severe disease in humans and animals. Environmental signals such as the accumulation of inorganic ions mediates the biofilm forming capabilities and survival of B. pseudomallei. We have previously shown that B. pseudomallei responds to nitrate and nitrite by inhibiting biofilm formation and altering cyclic di-GMP signaling. To better understand the roles of nitrate-sensing in the biofilm inhibitory phenotype of B. pseudomallei, we created in-frame deletions of narX (Bp1026b_I1014) and narL (Bp1026b_I1013), which are adjacent components of a conserved nitrate-sensing two-component system. We observed transcriptional downregulation in key components of the biofilm matrix in response to nitrate and nitrite. Some of the most differentially expressed genes were nonribosomal peptide synthases (NRPS) and/or polyketide synthases (PKS) encoding the proteins for the biosynthesis of bactobolin, malleilactone, and syrbactin, and an uncharacterized cryptic NRPS biosynthetic cluster. RNA expression patterns were reversed in ∆narX and ∆narL mutants, suggesting that nitrate sensing is an important checkpoint for regulating the diverse metabolic changes occurring in the biofilm inhibitory phenotype. Moreover, in a macrophage model of infection, ∆narX and ∆narL mutants were attenuated in intracellular replication, suggesting that nitrate sensing contributes to survival in the host.
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Affiliation(s)
- Mihnea R Mangalea
- Department of Microbiology, Immunology, and Pathology, Colorado State University, Fort Collins, CO, 80523, USA
| | - Bradley R Borlee
- Department of Microbiology, Immunology, and Pathology, Colorado State University, Fort Collins, CO, 80523, USA.
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D'haeseleer P, Collette NM, Lao V, Segelke BW, Branda SS, Franco M. Shotgun Immunoproteomic Approach for the Discovery of Linear B-Cell Epitopes in Biothreat Agents Francisella tularensis and Burkholderia pseudomallei. Front Immunol 2021; 12:716676. [PMID: 34659206 PMCID: PMC8513525 DOI: 10.3389/fimmu.2021.716676] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2021] [Accepted: 09/02/2021] [Indexed: 11/13/2022] Open
Abstract
Peptide-based subunit vaccines are coming to the forefront of current vaccine approaches, with safety and cost-effective production among their top advantages. Peptide vaccine formulations consist of multiple synthetic linear epitopes that together trigger desired immune responses that can result in robust immune memory. The advantages of linear compared to conformational epitopes are their simple structure, ease of synthesis, and ability to stimulate immune responses by means that do not require complex 3D conformation. Prediction of linear epitopes through use of computational tools is fast and cost-effective, but typically of low accuracy, necessitating extensive experimentation to verify results. On the other hand, identification of linear epitopes through experimental screening has been an inefficient process that requires thorough characterization of previously identified full-length protein antigens, or laborious techniques involving genetic manipulation of organisms. In this study, we apply a newly developed generalizable screening method that enables efficient identification of B-cell epitopes in the proteomes of pathogenic bacteria. As a test case, we used this method to identify epitopes in the proteome of Francisella tularensis (Ft), a Select Agent with a well-characterized immunoproteome. Our screen identified many peptides that map to known antigens, including verified and predicted outer membrane proteins and extracellular proteins, validating the utility of this approach. We then used the method to identify seroreactive peptides in the less characterized immunoproteome of Select Agent Burkholderia pseudomallei (Bp). This screen revealed known Bp antigens as well as proteins that have not been previously identified as antigens. Although B-cell epitope prediction tools Bepipred 2.0 and iBCE-EL classified many of our seroreactive peptides as epitopes, they did not score them significantly higher than the non-reactive tryptic peptides in our study, nor did they assign higher scores to seroreactive peptides from known Ft or Bp antigens, highlighting the need for experimental data instead of relying on computational epitope predictions alone. The present workflow is easily adaptable to detecting peptide targets relevant to the immune systems of other mammalian species, including humans (depending upon the availability of convalescent sera from patients), and could aid in accelerating the discovery of B-cell epitopes and development of vaccines to counter emerging biological threats.
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Affiliation(s)
- Patrik D'haeseleer
- Biosciences and Biotechnology Division, Lawrence Livermore National Laboratory, Livermore, CA, United States
| | - Nicole M Collette
- Biosciences and Biotechnology Division, Lawrence Livermore National Laboratory, Livermore, CA, United States
| | - Victoria Lao
- Biosciences and Biotechnology Division, Lawrence Livermore National Laboratory, Livermore, CA, United States
| | - Brent W Segelke
- Biosciences and Biotechnology Division, Lawrence Livermore National Laboratory, Livermore, CA, United States
| | - Steven S Branda
- Molecular and Microbiology Department, Sandia National Laboratories, Livermore, CA, United States
| | - Magdalena Franco
- Biosciences and Biotechnology Division, Lawrence Livermore National Laboratory, Livermore, CA, United States
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11
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Mou S, Jenkins CC, Okaro U, Dhummakupt ES, Mach PM, DeShazer D. The Burkholderia pseudomallei hmqA-G Locus Mediates Competitive Fitness against Environmental Gram-Positive Bacteria. Microbiol Spectr 2021; 9:e0010221. [PMID: 34160272 PMCID: PMC8552763 DOI: 10.1128/spectrum.00102-21] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2021] [Accepted: 05/03/2021] [Indexed: 12/21/2022] Open
Abstract
Burkholderia pseudomallei is an opportunistic pathogen that is responsible for the disease melioidosis in humans and animals. The microbe is a tier 1 select agent because it is highly infectious by the aerosol route, it is inherently resistant to multiple antibiotics, and no licensed vaccine currently exists. Naturally acquired infections result from contact with contaminated soil or water sources in regions of endemicity. There have been few reports investigating the molecular mechanism(s) utilized by B. pseudomallei to survive and persist in ecological niches harboring microbial competitors. Here, we report the isolation of Gram-positive bacteria from multiple environmental sources and show that ∼45% of these isolates are inhibited by B. pseudomallei in head-to-head competition assays. Two competition-deficient B. pseudomallei transposon mutants were identified that contained insertion mutations in the hmqA-G operon. This large biosynthetic gene cluster encodes the enzymes that produce a family of secondary metabolites called 4-hydroxy-3-methyl-2-alkylquinolines (HMAQs). Liquid chromatography and mass spectrometry conducted on filter-sterilized culture supernatants revealed five HMAQs and N-oxide derivatives that were produced by the parental strain but were absent in an isogenic hmqD deletion mutant. The results demonstrate that B. pseudomallei inhibits the growth of environmental Gram-positive bacteria in a contact-independent manner via the production of HMAQs by the hmqA-G operon. IMPORTANCE Burkholderia pseudomallei naturally resides in water, soil, and the rhizosphere and its success as an opportunistic pathogen is dependent on the ability to persist in these harsh habitats long enough to come into contact with a susceptible host. In addition to adapting to limiting nutrients and diverse chemical and physical challenges, B. pseudomallei also has to interact with a variety of microbial competitors. Our research shows that one of the ways in which B. pseudomallei competes with Gram-positive environmental bacteria is by exporting a diverse array of closely related antimicrobial secondary metabolites.
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Affiliation(s)
- Sherry Mou
- Foundational Sciences Directorate, Bacteriology Division, United States Army Medical Research Institute of Infectious Diseases, Frederick, Maryland, USA
| | - Conor C. Jenkins
- Excet Inc., Springfield, Virginia, USA
- DEVCOM Chemical Biological Center, Aberdeen Proving Ground, Maryland, USA
| | - Udoka Okaro
- Foundational Sciences Directorate, Bacteriology Division, United States Army Medical Research Institute of Infectious Diseases, Frederick, Maryland, USA
| | | | - Phillip M. Mach
- DEVCOM Chemical Biological Center, Aberdeen Proving Ground, Maryland, USA
| | - David DeShazer
- Foundational Sciences Directorate, Bacteriology Division, United States Army Medical Research Institute of Infectious Diseases, Frederick, Maryland, USA
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12
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An Outer Membrane Vesicle-Adjuvanted Oral Vaccine Protects Against Lethal, Oral Salmonella Infection. Pathogens 2021; 10:pathogens10050616. [PMID: 34069796 PMCID: PMC8157261 DOI: 10.3390/pathogens10050616] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2021] [Revised: 05/14/2021] [Accepted: 05/16/2021] [Indexed: 11/23/2022] Open
Abstract
Non-typhoidal salmonellosis, caused by Salmonella enterica serovar Typhimurium is a common fecal-oral disease characterized by mild gastrointestinal distress resulting in diarrhea, chills, fever, abdominal cramps, head and body aches, nausea, and vomiting. Increasing incidences of antibiotic resistant invasive non-typhoidal Salmonella infections makes this a global threat requiring novel treatment strategies including next-generation vaccines. The goal of the current study was to formulate a novel vaccine platform against Salmonella infection that could be delivered orally. To accomplish this, we created a Salmonella-specific vaccine adjuvanted with Burkholderia pseudomallei outer membrane vesicles (OMVs). We show that adding OMVs to a heat-killed oral Salmonella vaccine (HKST + OMVs) protects against a lethal, oral challenge with Salmonella. Further, we show that opsonizing anti-Salmonella antibodies are induced in response to immunization and that CD4 T cells and B cells can be induced when OMVs are used as the oral adjuvant. This study represents a novel oral vaccine approach to combatting the increasing problem of invasive Salmonella infections.
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13
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Identification of a PadR-type regulator essential for intracellular pathogenesis of Burkholderia pseudomallei. Sci Rep 2021; 11:10405. [PMID: 34001967 PMCID: PMC8128862 DOI: 10.1038/s41598-021-89852-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2020] [Accepted: 04/28/2021] [Indexed: 11/14/2022] Open
Abstract
Burkholderia pseudomallei (Bp) is the causative agent of melioidosis, a disease endemic to the tropics. Melioidosis manifests in various ways ranging from acute skin lesions to pneumonia and, in rare cases, infection of the central nervous system. Bp is a facultative intracellular pathogen and it can infect various cell types. The Bp intracellular lifecycle has been partially elucidated and is highly complex. Herein, we have identified a transcriptional regulator, BP1026B_II1198, that is differentially expressed as Bp transits through host cells. A deletion mutant of BP1026B_II1198 was attenuated in RAW264.7 cell and BALB/c mouse infection. To further characterize the function of this transcriptional regulator, we endeavored to determine the regulon of BP1026B_II1198. RNA-seq analysis showed the global picture of genes regulated while ChIP-seq analysis identified two specific BP1026B_II1198 binding regions on chromosome II. We investigated the transposon mutants of these genes controlled by BP1026B_II1198 and confirmed that these genes contribute to pathogenesis in RAW264.7 murine macrophage cells. Taken together, the data presented here shed light on the regulon of BP1026B_II1198 and its role during intracellular infection and highlights an integral portion of the highly complex regulation network of Bp during host infection.
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14
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Khakhum N, Bharaj P, Walker DH, Torres AG, Endsley JJ. Antigen-specific antibody and polyfunctional T cells generated by respiratory immunization with protective Burkholderia ΔtonB Δhcp1 live attenuated vaccines. NPJ Vaccines 2021; 6:72. [PMID: 33986290 PMCID: PMC8119421 DOI: 10.1038/s41541-021-00333-4] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2020] [Accepted: 03/18/2021] [Indexed: 11/09/2022] Open
Abstract
Melioidosis, caused by Burkholderia pseudomallei (Bpm), lacks a vaccine. We identify the immune correlates of protection induced by B. mallei ΔtonB Δhcp1 (CLH001) and Bpm ΔtonB Δhcp1 (PBK001) vaccines against inhalational melioidosis. Mucosal immunization with either vaccine generates Bpm-specific IgM and IgG (IgG2b/c > IgG1 > IgG3) antibodies in sera and lungs, and lung IgA antibodies. Sera confers complement-independent bactericidal activity and macrophages opsonophagocytic uptake but is insufficient in passive transfer experiments to provide significant protection. Both vaccines elicit memory Th1 and Th17 CD4+ T-cell responses in lung and spleen after Bpm antigen-specific recall. The PBK001 vaccine is superior in generating respiratory IgA post-boost, anamnestic IgG at challenge, T-cell recall to specific antigen, and development of diverse polyfunctional memory T-cell pools. Analysis of lung histology suggests that potent polyfunctional T-cell memory and/or IL-17 signatures generated with PBK001 vaccination may be associated with moderate lung inflammation post vaccination.
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Affiliation(s)
- Nittaya Khakhum
- Department of Microbiology and Immunology, University of Texas Medical Branch, Galveston, TX, USA
| | - Preeti Bharaj
- Department of Microbiology and Immunology, University of Texas Medical Branch, Galveston, TX, USA
| | - David H Walker
- Department of Pathology, University of Texas Medical Branch, Galveston, TX, USA
| | - Alfredo G Torres
- Department of Microbiology and Immunology, University of Texas Medical Branch, Galveston, TX, USA. .,Department of Pathology, University of Texas Medical Branch, Galveston, TX, USA.
| | - Janice J Endsley
- Department of Microbiology and Immunology, University of Texas Medical Branch, Galveston, TX, USA.
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15
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Heacock-Kang Y, McMillan IA, Norris MH, Sun Z, Zarzycki-Siek J, Bluhm AP, Cabanas D, Norton RE, Ketheesan N, Miller JF, Schweizer HP, Hoang TT. The Burkholderia pseudomallei intracellular 'TRANSITome'. Nat Commun 2021; 12:1907. [PMID: 33772012 PMCID: PMC7998038 DOI: 10.1038/s41467-021-22169-1] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2020] [Accepted: 02/26/2021] [Indexed: 01/01/2023] Open
Abstract
Prokaryotic cell transcriptomics has been limited to mixed or sub-population dynamics and individual cells within heterogeneous populations, which has hampered further understanding of spatiotemporal and stage-specific processes of prokaryotic cells within complex environments. Here we develop a 'TRANSITomic' approach to profile transcriptomes of single Burkholderia pseudomallei cells as they transit through host cell infection at defined stages, yielding pathophysiological insights. We find that B. pseudomallei transits through host cells during infection in three observable stages: vacuole entry; cytoplasmic escape and replication; and membrane protrusion, promoting cell-to-cell spread. The B. pseudomallei 'TRANSITome' reveals dynamic gene-expression flux during transit in host cells and identifies genes that are required for pathogenesis. We find several hypothetical proteins and assign them to virulence mechanisms, including attachment, cytoskeletal modulation, and autophagy evasion. The B. pseudomallei 'TRANSITome' provides prokaryotic single-cell transcriptomics information enabling high-resolution understanding of host-pathogen interactions.
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Affiliation(s)
- Yun Heacock-Kang
- School of Life Sciences, University of Hawai'i at Mānoa, Honolulu, HI, USA
| | - Ian A McMillan
- School of Life Sciences, University of Hawai'i at Mānoa, Honolulu, HI, USA
| | - Michael H Norris
- School of Life Sciences, University of Hawai'i at Mānoa, Honolulu, HI, USA
- Department of Geography and Emerging Pathogens Institute, University of Florida, Gainesville, FL, USA
| | - Zhenxin Sun
- School of Life Sciences, University of Hawai'i at Mānoa, Honolulu, HI, USA
| | - Jan Zarzycki-Siek
- School of Life Sciences, University of Hawai'i at Mānoa, Honolulu, HI, USA
| | - Andrew P Bluhm
- School of Life Sciences, University of Hawai'i at Mānoa, Honolulu, HI, USA
- Department of Geography and Emerging Pathogens Institute, University of Florida, Gainesville, FL, USA
| | - Darlene Cabanas
- School of Life Sciences, University of Hawai'i at Mānoa, Honolulu, HI, USA
| | - Robert E Norton
- Townsville Hospital, Townsville, QLD, Australia
- Faculty of Medicine, University of Queensland, Brisbane, Australia
| | - Natkunam Ketheesan
- Science and Technology, University of New England, New South Wales, Australia
| | - Jeff F Miller
- Department of Microbiology, Immunology, and Molecular Genetics, and the California NanoSystems Institute, University of California, Los Angeles, CA, USA
| | - Herbert P Schweizer
- Pathogen and Microbiome Institute, Northern Arizona University, Flagstaff, AZ, USA
| | - Tung T Hoang
- School of Life Sciences, University of Hawai'i at Mānoa, Honolulu, HI, USA.
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16
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Burkholderia pseudomallei OMVs derived from infection mimicking conditions elicit similar protection to a live-attenuated vaccine. NPJ Vaccines 2021; 6:18. [PMID: 33514749 PMCID: PMC7846723 DOI: 10.1038/s41541-021-00281-z] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2020] [Accepted: 01/07/2021] [Indexed: 02/07/2023] Open
Abstract
Burkholderia pseudomallei is a Gram-negative, facultative intracellular bacillus that causes the disease melioidosis. B. pseudomallei expresses a number of proteins that contribute to its intracellular survival in the mammalian host. We previously demonstrated that immunization with OMVs derived from B. pseudomallei grown in nutrient-rich media protects mice against lethal disease. Here, we evaluated if OMVs derived from B. pseudomallei grown under macrophage-mimicking growth conditions could be enriched with intracellular-stage proteins in order to improve the vaccine. We show that OMVs produced in this manner (M9 OMVs) contain proteins associated with intracellular survival yet are non-toxic to living cells. Immunization of mice provides significant protection against pulmonary infection similar to that achieved with a live attenuated vaccine and is associated with increased IgG, CD4+, and CD8+ T cells. OMVs possess inherent adjuvanticity and drive DC activation and maturation. These results indicate that M9 OMVs constitute a new promising vaccine against melioidosis.
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17
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Wang G, Zarodkiewicz P, Valvano MA. Current Advances in Burkholderia Vaccines Development. Cells 2020; 9:E2671. [PMID: 33322641 PMCID: PMC7762980 DOI: 10.3390/cells9122671] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2020] [Revised: 12/01/2020] [Accepted: 12/09/2020] [Indexed: 12/18/2022] Open
Abstract
The genus Burkholderia includes a wide range of Gram-negative bacterial species some of which are pathogenic to humans and other vertebrates. The most pathogenic species are Burkholderia mallei, Burkholderia pseudomallei, and the members of the Burkholderia cepacia complex (Bcc). B. mallei and B. pseudomallei, the cause of glanders and melioidosis, respectively, are considered potential bioweapons. The Bcc comprises a subset of Burkholderia species associated with respiratory infections in people with chronic granulomatous disease and cystic fibrosis. Antimicrobial treatment of Burkholderia infections is difficult due to the intrinsic multidrug antibiotic resistance of these bacteria; prophylactic vaccines provide an attractive alternative to counteract these infections. Although commercial vaccines against Burkholderia infections are still unavailable, substantial progress has been made over recent years in the development of vaccines against B. pseudomallei and B. mallei. This review critically discusses the current advances in vaccine development against B. mallei, B. pseudomallei, and the Bcc.
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Affiliation(s)
| | | | - Miguel A. Valvano
- Wellcome-Wolfson Institute for Experimental Medicine, Queen’s University Belfast, Belfast BT9 7BL, UK; (G.W.); (P.Z.)
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18
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Welkos S, Blanco I, Okaro U, Chua J, DeShazer D. A DUF4148 family protein produced inside RAW264.7 cells is a critical Burkholderia pseudomallei virulence factor. Virulence 2020; 11:1041-1058. [PMID: 32835600 PMCID: PMC7549894 DOI: 10.1080/21505594.2020.1806675] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2020] [Revised: 07/24/2020] [Accepted: 07/27/2020] [Indexed: 11/12/2022] Open
Abstract
Burkholderia pseudomallei: is the etiological agent of the disease melioidosis and is a Tier 1 select agent. It survives and replicates inside phagocytic cells by escaping from the endocytic vacuole, replicating in the cytosol, spreading to other cells via actin polymerization and promoting the fusion of infected and uninfected host cells to form multinucleated giant cells. In this study, we utilized a proteomics approach to identify bacterial proteins produced inside RAW264.7 murine macrophages and host proteins produced in response to B. pseudomallei infection. Cells infected with B. pseudomallei strain K96243 were lysed and the lysate proteins digested and analyzed using nanoflow reversed-phase liquid chromatography and tandem mass spectrometry. Approximately 160 bacterial proteins were identified in the infected macrophages, including BimA, TssA, TssB, Hcp1 and TssM. Several previously uncharacterized B. pseudomallei proteins were also identified, including BPSS1996 and BPSL2748. Mutations were constructed in the genes encoding these novel proteins and their relative virulence was assessed in BALB/c mice. The 50% lethal dose for the BPSS1996 mutant was approximately 55-fold higher than that of the wild type, suggesting that BPSS1996 is required for full virulence. Sera from B. pseudomallei-infected animals reacted with BPSS1996 and it was found to localize to the bacterial surface using indirect immunofluorescence. Finally, we identified 274 host proteins that were exclusively present or absent in infected RAW264.7 cells, including chemokines and cytokines involved in controlling the initial stages of infection.
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Affiliation(s)
- Susan Welkos
- Bacteriology Division, United States Army Medical Research Institute of Infectious Diseases, Frederick, Maryland, USA
| | - Irma Blanco
- Bacteriology Division, United States Army Medical Research Institute of Infectious Diseases, Frederick, Maryland, USA
| | - Udoka Okaro
- Bacteriology Division, United States Army Medical Research Institute of Infectious Diseases, Frederick, Maryland, USA
| | - Jennifer Chua
- Bacteriology Division, United States Army Medical Research Institute of Infectious Diseases, Frederick, Maryland, USA
| | - David DeShazer
- Bacteriology Division, United States Army Medical Research Institute of Infectious Diseases, Frederick, Maryland, USA
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19
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Amiss AS, Webb JR, Mayo M, Currie BJ, Craik DJ, Henriques ST, Lawrence N. Safer In Vitro Drug Screening Models for Melioidosis Therapy Development. Am J Trop Med Hyg 2020; 103:1846-1851. [PMID: 32975176 DOI: 10.4269/ajtmh.20-0248] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Melioidosis is a neglected tropical disease caused by the Gram-negative soil bacterium Burkholderia pseudomallei. Current antibiotic regimens used to treat melioidosis are prolonged and expensive, and often ineffective because of intrinsic and acquired antimicrobial resistance. Efforts to develop new treatments for melioidosis are limited by the risks associated with handling pathogenic B. pseudomallei, which restricts research to facilities with biosafety level three containment. Closely related nonpathogenic Burkholderia can be investigated under less stringent biosafety level two containment, and we hypothesized that they could be used as model organisms for developing therapies that would also be effective against B. pseudomallei. We used microbroth dilution assays to compare drug susceptibility profiles of three B. pseudomallei strains and five nonpathogenic Burkholderia strains. Burkholderia humptydooensis, Burkholderia thailandensis, and Burkholderia territorii had similar susceptibility profiles to pathogenic B. pseudomallei that support their potential as safer in vitro models for developing new melioidosis therapies.
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Affiliation(s)
- Anna S Amiss
- Institute for Molecular Bioscience, The University of Queensland, Brisbane, Australia
| | - Jessica R Webb
- Global and Tropical Health Division, Menzies School of Health Research, Darwin, Australia
| | - Mark Mayo
- Global and Tropical Health Division, Menzies School of Health Research, Darwin, Australia
| | - Bart J Currie
- Northern Territory Medical Program, Department of Infectious Diseases, Royal Darwin Hospital, Darwin, Australia.,Global and Tropical Health Division, Menzies School of Health Research, Darwin, Australia
| | - David J Craik
- Institute for Molecular Bioscience, The University of Queensland, Brisbane, Australia
| | - Sónia Troeira Henriques
- Queensland University of Technology, School of Biomedical Sciences, Institute of Healthy and Biomedical Innovation, and Translational Research Institute, Brisbane, Queensland, Australia.,Institute for Molecular Bioscience, The University of Queensland, Brisbane, Australia
| | - Nicole Lawrence
- Institute for Molecular Bioscience, The University of Queensland, Brisbane, Australia
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20
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Grund ME, Choi SJ, McNitt DH, Barbier M, Hu G, LaSala PR, Cote CK, Berisio R, Lukomski S. Burkholderia collagen-like protein 8, Bucl8, is a unique outer membrane component of a putative tetrapartite efflux pump in Burkholderia pseudomallei and Burkholderia mallei. PLoS One 2020; 15:e0242593. [PMID: 33227031 PMCID: PMC7682875 DOI: 10.1371/journal.pone.0242593] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2020] [Accepted: 11/06/2020] [Indexed: 12/19/2022] Open
Abstract
Bacterial efflux pumps are an important pathogenicity trait because they extrude a variety of xenobiotics. Our laboratory previously identified in silico Burkholderia collagen-like protein 8 (Bucl8) in the hazardous pathogens Burkholderia pseudomallei and Burkholderia mallei. We hypothesize that Bucl8, which contains two predicted tandem outer membrane efflux pump domains, is a component of a putative efflux pump. Unique to Bucl8, as compared to other outer membrane proteins, is the presence of an extended extracellular region containing a collagen-like (CL) domain and a non-collagenous C-terminus (Ct). Molecular modeling and circular dichroism spectroscopy with a recombinant protein, corresponding to this extracellular CL-Ct portion of Bucl8, demonstrated that it adopts a collagen triple helix, whereas functional assays screening for Bucl8 ligands identified binding to fibrinogen. Bioinformatic analysis of the bucl8 gene locus revealed it resembles a classical efflux-pump operon. The bucl8 gene is co-localized with downstream fusCDE genes encoding fusaric acid (FA) resistance, and with an upstream gene, designated as fusR, encoding a LysR-type transcriptional regulator. Using reverse transcriptase (RT)-qPCR, we defined the boundaries and transcriptional organization of the fusR-bucl8-fusCDE operon. We found exogenous FA induced bucl8 transcription over 80-fold in B. pseudomallei, while deletion of the entire bucl8 locus decreased the minimum inhibitory concentration of FA 4-fold in its isogenic mutant. We furthermore showed that the putative Bucl8-associated pump expressed in the heterologous Escherichia coli host confers FA resistance. On the contrary, the Bucl8-associated pump did not confer resistance to a panel of clinically-relevant antimicrobials in Burkholderia and E. coli. We finally demonstrated that deletion of the bucl8-locus drastically affects the growth of the mutant in L-broth. We determined that Bucl8 is a component of a novel tetrapartite efflux pump, which confers FA resistance, fibrinogen binding, and optimal growth.
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Affiliation(s)
- Megan E. Grund
- Department of Microbiology, Immunology and Cell Biology, School of
Medicine, West Virginia University, Morgantown, WV, United States of
America
| | - Soo J. Choi
- Department of Microbiology, Immunology and Cell Biology, School of
Medicine, West Virginia University, Morgantown, WV, United States of
America
| | - Dudley H. McNitt
- Department of Microbiology, Immunology and Cell Biology, School of
Medicine, West Virginia University, Morgantown, WV, United States of
America
| | - Mariette Barbier
- Department of Microbiology, Immunology and Cell Biology, School of
Medicine, West Virginia University, Morgantown, WV, United States of
America
| | - Gangqing Hu
- Department of Microbiology, Immunology and Cell Biology, School of
Medicine, West Virginia University, Morgantown, WV, United States of
America
- Cancer Center, West Virginia University, Morgantown, WV, United States of
America
- Bioinformatics Core, West Virginia University, Morgantown, WV, United
States of America
| | - P. Rocco LaSala
- Department of Pathology, West Virginia University, Morgantown, WV, United
States of America
| | - Christopher K. Cote
- Bacteriology Division, The United States Army Medical Research Institute
of Infectious Diseases (USAMRIID), Frederick, MD, United States of
America
| | - Rita Berisio
- Institute of Biostructures and Bioimaging, National Research Council,
Naples, Italy
| | - Slawomir Lukomski
- Department of Microbiology, Immunology and Cell Biology, School of
Medicine, West Virginia University, Morgantown, WV, United States of
America
- Cancer Center, West Virginia University, Morgantown, WV, United States of
America
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21
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Schully KL, Young CC, Mayo M, Connolly AL, Rigas V, Spall A, Chan AA, Salvador MG, Lawler JV, Opdyke JA, Clark DV, Currie BJ. Next-generation Diagnostics for Melioidosis: Evaluation of a Prototype i-STAT Cartridge to Detect Burkholderia pseudomallei Biomarkers. Clin Infect Dis 2020; 69:421-427. [PMID: 30403768 DOI: 10.1093/cid/ciy929] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2018] [Accepted: 10/29/2018] [Indexed: 11/12/2022] Open
Abstract
BACKGROUND Infection with the gram-negative bacterium Burkholderia pseudomallei can result in melioidosis, a life-threatening disease that can be difficult to diagnose. Culture remains the gold standard for diagnosis but requires laboratory resources not available in many endemic regions. A lateral flow immunoassay has shown promise for POC diagnostics but suffers from low sensitivity when used on blood samples. PCR also has low sensitivity on blood, attributed to the low bacterial numbers in blood observed in melioidosis patients, even when bacteraemic. METHODS A prototype i-STAT cartridge was developed to utilize the monoclonal antibody specific for the capsule of pathogenic Burkholderia species employed on the LFI. The resulting POC assay was evaluated on 414 clinical specimens from Darwin, Australia and Cambodia. RESULTS The i-STAT assay accurately distinguished Australian blood culture positive melioidosis patients from Australian patients hospitalized with other infections (AUC = 0.91, 95% CI 0.817 - 1.0). We derived an assay cutoff with 76% sensitivity and 94% specificity that correctly classified 88% (n = 74) of the Australian patients. Interestingly, only 46% (6/13) of the culture-positive melioidosis patients in Cambodia were classified correctly. Of great importance however, the assay detected capsule from blood samples for 32% of blood culture negative melioidosis patients in both cohorts and previously undiagnosed melioidosis patients in Cambodia. In addition the assay showed high sensitivity and specificity for urine, pus and sputum. CONCLUSIONS Diagnostic tools that are not dependent upon the growth kinetics or the levels of bacteremia of B. pseudomallei represent the next-generation of diagnostics and must be pursued further.
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Affiliation(s)
- Kevin L Schully
- Austere Environments Consortium for Enhanced Sepsis Outcomes, Biological Defense Research Directorate, Naval Medical Research Center-Frederick, Ft. Detrick
| | - Charles C Young
- Johns Hopkins University Applied Physics Laboratory, Laurel, Maryland
| | - Mark Mayo
- Global and Tropical Health Division, Menzies School of Health Research, Darwin, Australia
| | - Amy L Connolly
- Johns Hopkins University Applied Physics Laboratory, Laurel, Maryland
| | - Vanessa Rigas
- Global and Tropical Health Division, Menzies School of Health Research, Darwin, Australia
| | - Ammarah Spall
- Austere Environments Consortium for Enhanced Sepsis Outcomes, Biological Defense Research Directorate, Naval Medical Research Center-Frederick, Ft. Detrick
| | - Alyssa A Chan
- Austere Environments Consortium for Enhanced Sepsis Outcomes, Biological Defense Research Directorate, Naval Medical Research Center-Frederick, Ft. Detrick
| | - Mark G Salvador
- Austere Environments Consortium for Enhanced Sepsis Outcomes, Biological Defense Research Directorate, Naval Medical Research Center-Frederick, Ft. Detrick
| | - James V Lawler
- Austere Environments Consortium for Enhanced Sepsis Outcomes, Biological Defense Research Directorate, Naval Medical Research Center-Frederick, Ft. Detrick
| | - Jason A Opdyke
- Joint Program Executive Office for Chemical, Biological, Radiological and Nuclear Defense, Medical Countermeasure Systems, Ft. Detrick, Maryland
| | - Danielle V Clark
- Austere Environments Consortium for Enhanced Sepsis Outcomes, Biological Defense Research Directorate, Naval Medical Research Center-Frederick, Ft. Detrick
| | - Bart J Currie
- Global and Tropical Health Division, Menzies School of Health Research, Darwin, Australia.,Department of Infectious Diseases and Northern Territory Medical Program, Royal Darwin Hospital, Australia
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22
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Cheung-Lee WL, Parry ME, Zong C, Cartagena AJ, Darst SA, Connell ND, Russo R, Link AJ. Discovery of Ubonodin, an Antimicrobial Lasso Peptide Active against Members of the Burkholderia cepacia Complex. Chembiochem 2020; 21:1335-1340. [PMID: 31765515 PMCID: PMC7205569 DOI: 10.1002/cbic.201900707] [Citation(s) in RCA: 39] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2019] [Indexed: 11/09/2022]
Abstract
We report the heterologous expression, structure, and antimicrobial activity of a lasso peptide, ubonodin, encoded in the genome of Burkholderia ubonensis. The topology of ubonodin is unprecedented amongst lasso peptides, with 18 of its 28 amino acids found in the mechanically bonded loop segment. Ubonodin inhibits RNA polymerase in vitro and has potent antimicrobial activity against several pathogenic members of the Burkholderia genus, most notably B. cepacia and B. multivorans, causative agents of lung infections in cystic fibrosis patients.
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Affiliation(s)
- Wai Ling Cheung-Lee
- Department of Chemical and Biological Engineering, Princeton University, 207 Hoyt Laboratory, Princeton, NJ, 08544, USA
| | - Madison E Parry
- Department of Chemical and Biological Engineering, Princeton University, 207 Hoyt Laboratory, Princeton, NJ, 08544, USA
| | - Chuhan Zong
- Department of Chemistry, Princeton University, 207 Hoyt Laboratory, Princeton, NJ, 08544, USA
| | - Alexis Jaramillo Cartagena
- Laboratory of Molecular Biophysics and, Tri-Institutional Training Program in Chemical Biology, Rockefeller University, 1230 York Ave., New York, NY, 10065, USA
| | - Seth A Darst
- Laboratory of Molecular Biophysics and, Tri-Institutional Training Program in Chemical Biology, Rockefeller University, 1230 York Ave., New York, NY, 10065, USA
| | - Nancy D Connell
- Center for Health Security, Johns Hopkins Bloomberg School of Public Health, 621 E. Pratt St. Suite 210, Baltimore, MD, 21202, USA
| | - Riccardo Russo
- Center for Emerging Pathogens, Division of Infectious Disease, New Jersey Medical School, Rutgers Biomedical and Health Sciences University, 185 South Orange Ave., Newark, NJ, 07103, USA
| | - A James Link
- Department of Chemical and Biological Engineering, Princeton University, 207 Hoyt Laboratory, Princeton, NJ, 08544, USA
- Department of Chemistry, Princeton University, 207 Hoyt Laboratory, Princeton, NJ, 08544, USA
- Department of Molecular Biology, Princeton University, 207 Hoyt Laboratory, Princeton, NJ, 08544, USA
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23
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Amemiya K, Dankmeyer JL, Biryukov SS, Treviño SR, Klimko CP, Mou SM, Fetterer DP, Garnes PG, Cote CK, Worsham PL, DeShazer D. Deletion of Two Genes in Burkholderia pseudomallei MSHR668 That Target Essential Amino Acids Protect Acutely Infected BALB/c Mice and Promote Long Term Survival. Vaccines (Basel) 2019; 7:vaccines7040196. [PMID: 31779073 PMCID: PMC6963190 DOI: 10.3390/vaccines7040196] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2019] [Revised: 10/31/2019] [Accepted: 11/15/2019] [Indexed: 12/25/2022] Open
Abstract
Melioidosis is an emerging disease that is caused by the facultative intracellular pathogen Burkholderia pseudomallei. It is intrinsically resistant to many antibiotics and host risk factors play a major role in susceptibility to infection. Currently, there is no human or animal vaccine against melioidosis. In this study, multiple B. pseudomallei MSHR668 deletion mutants were evaluated as live attenuated vaccines in the sensitive BALB/c mouse model of melioidosis. The most efficacious vaccines after an intraperitoneal challenge with 50-fold over the 50% median lethal dose (MLD50) with B. pseudomallei K96243 were 668 ΔhisF and 668 ΔilvI. Both vaccines completely protected mice in the acute phase of infection and showed significant protection (50% survivors) during the chronic phase of infection. The spleens of the survivors that were examined were sterile. Splenocytes from mice vaccinated with 668 ΔhisF and 668 ΔilvI expressed higher amounts of IFN-γ after stimulation with B. pseudomallei antigens than splenocytes from mice vaccinated with less protective candidates. Finally, we demonstrate that 668 ΔhisF is nonlethal in immunocompromised NOD/SCID mice. Our results show that 668 ΔhisF and 668 ΔilvI provide protective cell-mediated immune responses in the acute phase of infection and promote long term survival in the sensitive BALB/c mouse model of melioidosis.
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Affiliation(s)
- Kei Amemiya
- Bacteriology Division, United States Army Medical Research Institute of Infectious Diseases, Frederick, MD 21702, USA; (K.A.); (J.L.D.); (S.S.B.); (S.R.T.); (C.P.K.); (S.M.M.); (C.K.C.); (P.L.W.)
| | - Jennifer L. Dankmeyer
- Bacteriology Division, United States Army Medical Research Institute of Infectious Diseases, Frederick, MD 21702, USA; (K.A.); (J.L.D.); (S.S.B.); (S.R.T.); (C.P.K.); (S.M.M.); (C.K.C.); (P.L.W.)
| | - Sergei S. Biryukov
- Bacteriology Division, United States Army Medical Research Institute of Infectious Diseases, Frederick, MD 21702, USA; (K.A.); (J.L.D.); (S.S.B.); (S.R.T.); (C.P.K.); (S.M.M.); (C.K.C.); (P.L.W.)
| | - Sylvia R. Treviño
- Bacteriology Division, United States Army Medical Research Institute of Infectious Diseases, Frederick, MD 21702, USA; (K.A.); (J.L.D.); (S.S.B.); (S.R.T.); (C.P.K.); (S.M.M.); (C.K.C.); (P.L.W.)
| | - Christopher P. Klimko
- Bacteriology Division, United States Army Medical Research Institute of Infectious Diseases, Frederick, MD 21702, USA; (K.A.); (J.L.D.); (S.S.B.); (S.R.T.); (C.P.K.); (S.M.M.); (C.K.C.); (P.L.W.)
| | - Sherry M. Mou
- Bacteriology Division, United States Army Medical Research Institute of Infectious Diseases, Frederick, MD 21702, USA; (K.A.); (J.L.D.); (S.S.B.); (S.R.T.); (C.P.K.); (S.M.M.); (C.K.C.); (P.L.W.)
| | - David P. Fetterer
- Biostatistical Services, United States Army Medical Research Institute of Infectious Diseases, Frederick, MD 21702, USA; (D.P.F.); (P.G.G.)
| | - Preston G. Garnes
- Biostatistical Services, United States Army Medical Research Institute of Infectious Diseases, Frederick, MD 21702, USA; (D.P.F.); (P.G.G.)
| | - Christopher K. Cote
- Bacteriology Division, United States Army Medical Research Institute of Infectious Diseases, Frederick, MD 21702, USA; (K.A.); (J.L.D.); (S.S.B.); (S.R.T.); (C.P.K.); (S.M.M.); (C.K.C.); (P.L.W.)
| | - Patricia L. Worsham
- Bacteriology Division, United States Army Medical Research Institute of Infectious Diseases, Frederick, MD 21702, USA; (K.A.); (J.L.D.); (S.S.B.); (S.R.T.); (C.P.K.); (S.M.M.); (C.K.C.); (P.L.W.)
| | - David DeShazer
- Bacteriology Division, United States Army Medical Research Institute of Infectious Diseases, Frederick, MD 21702, USA; (K.A.); (J.L.D.); (S.S.B.); (S.R.T.); (C.P.K.); (S.M.M.); (C.K.C.); (P.L.W.)
- Correspondence: ; Tel.: +1-301-619-4919
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24
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Shearer JD, Saylor ML, Butler CM, Treston AM, Heine HS, Chirakul S, Schweizer HP, Louie A, Drusano GL, Zumbrun SD, Warfield KL. GC-072: A Novel Therapeutic Candidate for Oral Treatment of Melioidosis and Infections Caused by Select Biothreat Pathogens. Antimicrob Agents Chemother 2019; 63:AAC.00834-19. [PMID: 31548183 PMCID: PMC6879241 DOI: 10.1128/aac.00834-19] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2019] [Accepted: 09/13/2019] [Indexed: 12/03/2022] Open
Abstract
Burkholderia pseudomallei (B. pseudomallei), the etiological agent of melioidosis, is a Gram-negative bacterium with additional concern as a biothreat pathogen. The mortality rate from B. pseudomallei varies depending on the type of infection and extent of available health care, but in the case of septicemia left untreated it can range from 50 - 90%. Current therapy for melioidosis is biphasic, consisting of parenteral acute-phase treatment for two weeks or longer, followed by oral eradication-phase treatment lasting several months. An effective oral therapeutic for outpatient treatment of acute-phase melioidosis is needed. GC-072 is a potent, 4-oxoquinolizine antibiotic with selective inhibitory activity against bacterial topoisomerases. GC-072 has demonstrated in vitro potency against susceptible and drug-resistant strains of B. pseudomallei and is also active against Burkholderia mallei, Bacillus anthracis, Yersinia pestis, and Francisella tularensis GC-072 is bactericidal both extra- and intracellularly, with rapid killing noted within a few hours and reduced development of resistance compared to ceftazidime. GC-072, delivered intragastrically to mimic oral administration, promoted dose-dependent survival in mice using lethal inhalational models of B. pseudomallei infection following exposure to a 24 or 339 LD50 challenge with B. pseudomallei strain 1026b. Overall, GC-072 appears to be a strong candidate for first-line, oral treatment of melioidosis.
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Affiliation(s)
| | | | | | | | - Henry S Heine
- Institute for Therapeutic Innovation, University of Florida, College of Medicine, Orlando, FL
| | - Sunisa Chirakul
- Emerging Pathogens Institute, University of Florida, College of Medicine, Gainesville, FL
| | - Herbert P Schweizer
- Institute for Therapeutic Innovation, University of Florida, College of Medicine, Orlando, FL
- Emerging Pathogens Institute, University of Florida, College of Medicine, Gainesville, FL
| | - Arnold Louie
- Institute for Therapeutic Innovation, University of Florida, College of Medicine, Orlando, FL
| | - George L Drusano
- Institute for Therapeutic Innovation, University of Florida, College of Medicine, Orlando, FL
| | - Steven D Zumbrun
- United States Army Medical Research Institute of Infectious Diseases, Frederick MD
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Khakhum N, Bharaj P, Myers JN, Tapia D, Walker DH, Endsley JJ, Torres AG. Evaluation of Burkholderia mallei ΔtonB Δhcp1 (CLH001) as a live attenuated vaccine in murine models of glanders and melioidosis. PLoS Negl Trop Dis 2019; 13:e0007578. [PMID: 31306423 PMCID: PMC6658008 DOI: 10.1371/journal.pntd.0007578] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2019] [Revised: 07/25/2019] [Accepted: 06/25/2019] [Indexed: 01/01/2023] Open
Abstract
Background Glanders caused by Burkholderia mallei is a re-emerging zoonotic disease affecting solipeds and humans. Furthermore, B. mallei is genetically related to B. pseudomallei, which is the causative agent of melioidosis. Both facultative intracellular bacteria are classified as tier 1 select biothreat agents. Our previous study with a B. mallei ΔtonB Δhcp1 (CLH001) live-attenuated vaccine demonstrated that it is attenuated, safe and protective against B. mallei wild-type strains in the susceptible BALB/c mouse model. Methodology/Principal finding In our current work, we evaluated the protective efficacy of CLH001 against glanders and melioidosis in the more disease-resistant C57BL/6 mouse strain. The humoral as well as cellular immune responses were also examined. We found that CLH001-immunized mice showed 100% survival against intranasal and aerosol challenge with B. mallei ATCC 23344. Moreover, this vaccine also afforded significant cross-protection against B. pseudomallei K96243, with low level bacterial burden detected in organs. Immunization with a prime and boost regimen of CLH001 induced significantly greater levels of total and subclasses of IgG, and generated antigen-specific splenocyte production of IFN-γ and IL-17A. Interestingly, protection induced by CLH001 is primarily dependent on humoral immunity, while CD4+ and CD8+ T cells played a less critical protective role. Conclusions/Significance Our data indicate that CLH001 serves as an effective live attenuated vaccine to prevent glanders and melioidosis. The quantity and quality of antibody responses as well as improving cell-mediated immune responses following vaccination need to be further investigated prior to advancement to preclinical studies. Glanders (caused by Burkholderia. mallei) and melioidosis (caused by B. pseudomallei) are severe infectious diseases of concern worldwide because of the rising number of cases and mortality rate. The low infectious doses of these two pathogens along with their amenability for aerosolization are factors that could be exploited as potential biothreat agents. Once the diseases have developed in humans and animals, intrinsic resistance to broad classes of antibiotics becomes a challenge for treatment and increases the risk for relapse. The progress in vaccine development demonstrates that live attenuated vaccine strains are the most effective in protection and providing long-lasting immune responses against both diseases. Our data indicate that the B. mallei double mutant (ΔtonB Δhcp1) strain CLH001, is a feasible vaccine candidate to prevent glanders and melioidosis, especially for biodefense and public health purposes.
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Affiliation(s)
- Nittaya Khakhum
- Department of Microbiology and Immunology, University of Texas Medical Branch, Galveston, Texas, United States of America
| | - Preeti Bharaj
- Department of Microbiology and Immunology, University of Texas Medical Branch, Galveston, Texas, United States of America
| | - Julia N. Myers
- Department of Microbiology and Immunology, University of Texas Medical Branch, Galveston, Texas, United States of America
| | - Daniel Tapia
- Department of Microbiology and Immunology, University of Texas Medical Branch, Galveston, Texas, United States of America
| | - David H. Walker
- Department of Pathology, University of Texas Medical Branch, Galveston, Texas, United States of America
| | - Janice J. Endsley
- Department of Microbiology and Immunology, University of Texas Medical Branch, Galveston, Texas, United States of America
| | - Alfredo G. Torres
- Department of Microbiology and Immunology, University of Texas Medical Branch, Galveston, Texas, United States of America
- Department of Pathology, University of Texas Medical Branch, Galveston, Texas, United States of America
- * E-mail:
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26
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Flagellin-independent effects of a Toll-like receptor 5 polymorphism in the inflammatory response to Burkholderia pseudomallei. PLoS Negl Trop Dis 2019; 13:e0007354. [PMID: 31067234 PMCID: PMC6527242 DOI: 10.1371/journal.pntd.0007354] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2018] [Revised: 05/20/2019] [Accepted: 04/02/2019] [Indexed: 01/07/2023] Open
Abstract
Background Toll-like receptors (TLRs) are sentinel receptors of the innate immune system. TLR4 detects bacterial lipopolysaccharide (LPS) and TLR5 detects bacterial flagellin. A common human nonsense polymorphism, TLR5:c.1174C>T, results in a non-functional TLR5 protein. Individuals carrying this variant have decreased mortality from melioidosis, infection caused by the flagellated Gram-negative bacterium Burkholderia pseudomallei. Although impaired flagellin-dependent signaling in carriers of TLR5:c.1174C>T is well established, this study tested the hypothesis that a functional effect of TLR5:c.1174C>T is flagellin-independent and involves LPS-TLR4 pathways. Methodology/Principal findings Whole blood from two independent cohorts of individuals genotyped at TLR5:c.1174C>T was stimulated with wild type or aflagellated B. pseudomallei or purified bacterial motifs followed by plasma cytokine measurements. Blood from individuals carrying the TLR5:c.1174C>T variant produced less IL-6 and IL-10 in response to an aflagellated B. pseudomallei mutant and less IL-8 in response to purified B. pseudomallei LPS than blood from individuals without the variant. TLR5 expression in THP1 cells was silenced using siRNA; these cells were stimulated with LPS before cytokine levels in cell supernatants were quantified by ELISA. In these cells following LPS stimulation, silencing of TLR5 with siRNA reduced both TNF-α and IL-8 levels. These effects were not explained by differences in TLR4 mRNA expression or NF-κB or IRF activation. Conclusions/Significance The effects of the common nonsense TLR5:c.1174C>T polymorphism on the host inflammatory response to B. pseudomallei may not be restricted to flagellin-driven pathways. Moreover, TLR5 may modulate TLR4-dependent cytokine production. While these results may have broader implications for the role of TLR5 in the innate immune response in melioidosis and other conditions, further studies of the mechanisms underlying these observations are required. Toll-like receptors (TLRs) are important receptors of the innate immune system. TLR4 detects bacterial lipopolysaccharide (LPS) and TLR5 detects bacterial flagellin. A common human polymorphism in TLR5 encodes a shortened protein and blunts the immune response to flagellin. Individuals carrying this variant have decreased mortality from melioidosis, infection caused by the flagellated Gram-negative bacterium Burkholderia pseudomallei. The mechanism of protection is not known. We tested the hypothesis that the observed effect of the polymorphism is independent of flagellin and involves LPS-TLR4 pathways. We found that blood from individuals carrying the polymorphism produced lower levels of cytokines IL-6 and IL-10 in response to an aflagellated B. pseudomallei mutant and less IL-8 in response to purified B. pseudomallei LPS than blood from individuals without the variant. We further observed that in THP1 cells stimulated with LPS, silencing of TLR5 with siRNA reduced levels of both TNF-α and IL-8. These effects were not explained by differences in TLR4 mRNA expression. We conclude that the effects of the TLR5 polymorphism on the host inflammatory response to B. pseudomallei may not be restricted to flagellin-driven pathways. These results provide insights into the role of TLR5 in the innate immune response in melioidosis and other conditions.
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27
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Morici L, Torres AG, Titball RW. Novel multi-component vaccine approaches for Burkholderia pseudomallei. Clin Exp Immunol 2019; 196:178-188. [PMID: 30963550 DOI: 10.1111/cei.13286] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/20/2018] [Indexed: 12/16/2022] Open
Abstract
Burkholderia pseudomallei is the causative agent of melioidosis. Historically believed to be a relatively rare human disease in tropical countries, a recent study estimated that, worldwide, there are approximately 165 000 human melioidosis cases per year, more than half of whom die. The bacterium is inherently resistant to many antibiotics and treatment of the disease is often protracted and ineffective. There is no licensed vaccine against melioidosis, but a vaccine is predicted to be of value if used in high-risk populations. There has been progress over the last decade in the pursuit of an effective vaccine against melioidosis. Animal models of disease including mouse and non-human primates have been developed, and these models show that antibody responses play a key role in protection against melioidosis. Surprisingly, although B. pseudomallei is an intracellular pathogen there is limited evidence that CD8+ T cells play a role in protection. It is evident that a multi-component vaccine, incorporating one or more protective antigens, will probably be essential for protection because of the pathogen's sophisticated virulence mechanisms as well as strain heterogeneity. Multi-component vaccines in development include glycoconjugates, multivalent subunit preparations, outer membrane vesicles and other nano/microparticle platforms and live-attenuated or inactivated bacteria. A consistent finding with vaccine candidates tested in mice is the ability to induce sterilizing immunity at low challenge doses and extended time to death at higher challenge doses. Further research to identify ways of eliciting more potent immune responses might provide a path for licensing an effective vaccine.
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Affiliation(s)
- L Morici
- Department of Microbiology and Immunology, Tulane University School of Medicine, New Orleans, LA, USA
| | - A G Torres
- Department of Microbiology and Immunology, University of Texas Medical Branch, Galveston, Texas, USA
| | - R W Titball
- College of Life and Environmental Science, University of Exeter, Exeter, UK
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28
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Blandford LE, Johnston EL, Sanderson JD, Wade WG, Lax AJ. Promoter orientation of the immunomodulatory Bacteroides fragilis capsular polysaccharide A (PSA) is off in individuals with inflammatory bowel disease (IBD). Gut Microbes 2019; 10:569-577. [PMID: 30732524 PMCID: PMC6748595 DOI: 10.1080/19490976.2018.1560755] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
Bacteroides fragilis is a member of the normal microbiota of the lower gastrointestinal tract, but some strains produce the putative tumourigenic B. fragilis toxin (BFT). In addition, B. fragilis can produce multiple capsular polysaccharides that comprise a microcapsule layer, including an immunomodulatory, zwitterionic, polysaccharide A (PSA) capable of stimulating anti-inflammatory interleukin-10 (IL-10) production. It is known that the PSA promoter can undergo inversion, thereby regulating the expression of PSA. A PCR digestion technique was used to investigate B. fragilis capsular PSA promoter orientation using human samples for the first time. It was found that approximately half of the B. fragilis population in a healthy patient population had PSA orientated in the 'ON' position. However, individuals with inflammatory bowel disease (IBD) had a significantly lower percentage of the B. fragilis population with PSA orientated 'ON' in comparison with the other patient cohorts studied. Similarly, the putative tumourigenic bft-positive B. fragilis populations were significantly associated with a lower proportion of the PSA promoter orientated 'ON'. These results suggest that the proportion of the B. fragilis population with the PSA promoter 'ON' may be an indicator of gastrointestinal health.
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Affiliation(s)
| | - Emma L. Johnston
- Department of Gastroenterology, Guy’s and St. Thomas NHS Foundation Trust and King’s College London, King’s College London, London, UK
| | - Jeremy D. Sanderson
- Department of Gastroenterology, Guy’s and St. Thomas NHS Foundation Trust and King’s College London, King’s College London, London, UK
| | - William G. Wade
- King’s College London, Dental Institute, Guy’s Hospital, London, UK
| | - Alistair J. Lax
- King’s College London, Dental Institute, Guy’s Hospital, London, UK,CONTACT Alistair J. Lax King’s College London, Dental Institute, Guy’s Hospital, London
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Yi J, Simpanya MF, Settles EW, Shannon AB, Hernandez K, Pristo L, Keener ME, Hornstra H, Busch JD, Soffler C, Brett PJ, Currie BJ, Bowen RA, Tuanyok A, Keim P. Caprine humoral response to Burkholderia pseudomallei antigens during acute melioidosis from aerosol exposure. PLoS Negl Trop Dis 2019; 13:e0006851. [PMID: 30811382 PMCID: PMC6411198 DOI: 10.1371/journal.pntd.0006851] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2018] [Revised: 03/11/2019] [Accepted: 01/09/2019] [Indexed: 11/29/2022] Open
Abstract
Burkholderia pseudomallei causes melioidosis, a common source of pneumonia and sepsis in Southeast Asia and Northern Australia that results in high mortality rates. A caprine melioidosis model of aerosol infection that leads to a systemic infection has the potential to characterize the humoral immune response. This could help identify immunogenic proteins for new diagnostics and vaccine candidates. Outbred goats may more accurately mimic human infection, in contrast to the inbred mouse models used to date. B. pseudomallei infection was delivered as an intratracheal aerosol. Antigenic protein profiling was generated from the infecting strain MSHR511. Humoral immune responses were analyzed by ELISA and western blot, and the antigenic proteins were identified by mass spectrometry. Throughout the course of the infection the assay results demonstrated a much greater humoral response with IgG antibodies, in both breadth and quantity, compared to IgM antibodies. Pre-infection sera showed multiple immunogenic proteins already reactive for IgG (7-20) and IgM (0-12) in most of the goats despite no previous exposure to B. pseudomallei. After infection, the number of IgG reactive proteins showed a marked increase as the disease progressed. Early stage infection (day 7) showed immune reaction to chaperone proteins (GroEL, EF-Tu, and DnaK). These three proteins were detected in all serum samples after infection, with GroEL immunogenically dominant. Seven common reactive antigens were selected for further analysis using ELISA. The heat shock protein GroEL1 elicited the strongest goat antibody immune response compared to the other six antigens. Most of the six antigens showed the peak IgM reactivity at day 14, whereas the IgG reactivity increased further as the disease progressed. An overall MSHR511 proteomic comparison between the goat model and human sera showed that many immune reactive proteins are common between humans and goats with melioidosis.
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Affiliation(s)
- Jinhee Yi
- The Pathogen and Microbiome Institute, Northern Arizona University, Flagstaff, Arizona, United States of America
| | - Mukoma F. Simpanya
- The Pathogen and Microbiome Institute, Northern Arizona University, Flagstaff, Arizona, United States of America
| | - Erik W. Settles
- The Pathogen and Microbiome Institute, Northern Arizona University, Flagstaff, Arizona, United States of America
| | - Austin B. Shannon
- The Pathogen and Microbiome Institute, Northern Arizona University, Flagstaff, Arizona, United States of America
| | - Karen Hernandez
- The Pathogen and Microbiome Institute, Northern Arizona University, Flagstaff, Arizona, United States of America
| | - Lauren Pristo
- The Pathogen and Microbiome Institute, Northern Arizona University, Flagstaff, Arizona, United States of America
| | - Mitchell E. Keener
- The Pathogen and Microbiome Institute, Northern Arizona University, Flagstaff, Arizona, United States of America
| | - Heidie Hornstra
- The Pathogen and Microbiome Institute, Northern Arizona University, Flagstaff, Arizona, United States of America
| | - Joseph D. Busch
- The Pathogen and Microbiome Institute, Northern Arizona University, Flagstaff, Arizona, United States of America
| | - Carl Soffler
- Department of Biomedical Sciences, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, Colorado, United States of America
| | - Paul J. Brett
- Department of Microbiology and Immunology, University of Nevada, Reno School of Medicine, Reno, Nevada, United States of America
| | - Bart J. Currie
- Menzies School of Health Research and Infectious Diseases Department, Royal Darwin Hospital, Darwin, Northern Territory, Australia
| | - Richard A. Bowen
- Department of Biomedical Sciences, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, Colorado, United States of America
| | - Apichai Tuanyok
- Department of Infectious Diseases and Immunology, College of Veterinary Medicine and Emerging Pathogens Institute, University of Florida, Gainesville, Florida, United States of America
| | - Paul Keim
- The Pathogen and Microbiome Institute, Northern Arizona University, Flagstaff, Arizona, United States of America
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30
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Burkholderia pseudomallei Δ tonB Δ hcp1 Live Attenuated Vaccine Strain Elicits Full Protective Immunity against Aerosolized Melioidosis Infection. mSphere 2019; 4:4/1/e00570-18. [PMID: 30602524 PMCID: PMC6315081 DOI: 10.1128/msphere.00570-18] [Citation(s) in RCA: 32] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
In recent years, an increasing number of melioidosis cases have been reported in several regions where melioidosis is endemic and in areas where melioidosis had not commonly been diagnosed. Currently, the estimated burden of disease is around 165,000 new cases annually, including 89,000 cases that have fatal outcomes. This life-threatening infectious disease is caused by B. pseudomallei, which is classified as a Tier 1 select agent. Due to the high case fatality rate, intrinsic resistance to multiple antibiotic treatments, susceptibility to infection via the aerosol route, and potential use as a bioweapon, we have developed an effective live attenuated PBK001 vaccine capable of protecting against aerosolized melioidosis. Burkholderia pseudomallei is a Gram-negative facultative intracellular bacterium and the causative agent of melioidosis, a severe infectious disease found throughout the tropics. This organism is closely related to Burkholderia mallei, the etiological agent of glanders disease which primarily affects equines. These two pathogenic bacteria are classified as Tier 1 select agents due to their amenability to aerosolization, limited treatment options, and lack of an effective vaccine. We have previously successfully demonstrated the immunogenicity and protective efficacy of a live attenuated vaccine strain, B. malleiΔtonB Δhcp1 (CLH001). Thus, we applied this successful approach to the development of a similar vaccine against melioidosis by constructing the B. pseudomalleiΔtonB Δhcp1 (PBK001) strain. C57BL/6 mice were vaccinated intranasally with the live attenuated PBK001 strain and then challenged with wild-type B. pseudomallei K96243 by the aerosol route. Immunization with strain PBK001 resulted in full protection (100% survival) against acute aerosolized melioidosis with very low bacterial burden as observed in the lungs, livers, and spleens of immunized mice. PBK001 vaccination induced strong production of B. pseudomallei-specific serum IgG antibodies and both Th1 and Th17 CD4+ T cell responses. Further, humoral immunity appeared to be essential for vaccine-induced protection, whereas CD4+ and CD8+ T cells played a less direct immune role. Overall, PBK001 was shown to be an effective attenuated vaccine strain that activates a robust immune response and offers full protection against aerosol infection with B. pseudomallei. IMPORTANCE In recent years, an increasing number of melioidosis cases have been reported in several regions where melioidosis is endemic and in areas where melioidosis had not commonly been diagnosed. Currently, the estimated burden of disease is around 165,000 new cases annually, including 89,000 cases that have fatal outcomes. This life-threatening infectious disease is caused by B. pseudomallei, which is classified as a Tier 1 select agent. Due to the high case fatality rate, intrinsic resistance to multiple antibiotic treatments, susceptibility to infection via the aerosol route, and potential use as a bioweapon, we have developed an effective live attenuated PBK001 vaccine capable of protecting against aerosolized melioidosis.
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McLaughlin HP, Sue D. Rapid antimicrobial susceptibility testing and β-lactam-induced cell morphology changes of Gram-negative biological threat pathogens by optical screening. BMC Microbiol 2018; 18:218. [PMID: 30563467 PMCID: PMC6299660 DOI: 10.1186/s12866-018-1347-9] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2018] [Accepted: 11/16/2018] [Indexed: 12/20/2022] Open
Abstract
BACKGROUND For Yersinia pestis, Burkholderia pseudomallei, and Burkholderia mallei, conventional broth microdilution (BMD) is considered the gold standard for antimicrobial susceptibility testing (AST) and, depending on the species, requires an incubation period of 16-20 h, or 24-48 h according to the Clinical and Laboratory Standards Institute (CLSI) guidelines. After a diagnosis of plague, melioidosis or glanders during an outbreak or after an exposure event, the timely distribution of appropriate antibiotics for treatment or post-exposure prophylaxis of affected populations could reduce mortality rates. RESULTS Herein, we developed and evaluated a rapid, automated susceptibility test for these Gram-negative bacterial pathogens based on time-lapse imaging of cells incubating in BMD microtitre drug panels using an optical screening instrument (oCelloScope). In real-time, the instrument screened each inoculated well containing broth with various concentrations of antibiotics published by CLSI for primary testing: ciprofloxacin (CIP), doxycycline (DOX) and gentamicin (GEN) for Y. pestis; imipenem (IPM), ceftazidime (CAZ) and DOX for B. mallei; and IPM, DOX, CAZ, amoxicillin-clavulanic acid (AMC) and trimethoprim-sulfamethoxazole (SXT) for B. pseudomallei. Based on automated growth kinetic data, the time required to accurately determine susceptibility decreased by ≥70% for Y. pestis and ≥ 50% for B. mallei and B. pseudomallei compared to the times required for conventional BMD testing. Susceptibility to GEN, IPM and DOX could be determined in as early as three to six hours. In the presence of CAZ, susceptibility based on instrument-derived growth values could not be determined for the majority of B. pseudomallei and B. mallei strains tested. Time-lapse video imaging of these cultures revealed that the formation of filaments in the presence of this cephalosporin at inhibitory concentrations was detected as growth. Other β-lactam-induced cell morphology changes, such as the formation of spheroplasts and rapid cell lysis, were also observed and appear to be strain- and antibiotic concentration-dependent. CONCLUSIONS A rapid, functional AST was developed and real-time video footage captured β-lactam-induced morphologies of wild-type B. mallei and B. pseudomallei strains in broth. Optical screening reduced the time to results required for AST of three Gram-negative biothreat pathogens using clinically relevant, first-line antibiotics compared to conventional BMD.
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Affiliation(s)
- Heather P. McLaughlin
- Laboratory of Preparedness and Response Branch, Division of Preparedness and Emerging Infections, National Center for Emerging and Zoonotic Infectious Diseases, Centers for Disease Control and Prevention, 1600 Clifton Road NE, MS-H17-5, Atlanta, GA 30333 USA
| | - David Sue
- Laboratory of Preparedness and Response Branch, Division of Preparedness and Emerging Infections, National Center for Emerging and Zoonotic Infectious Diseases, Centers for Disease Control and Prevention, 1600 Clifton Road NE, MS-H17-5, Atlanta, GA 30333 USA
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Weppelmann TA, Norris MH, von Fricken ME, Rahman Khan MS, Okech BA, Cannella AP, Schweizer HP, Sanford DC, Tuanyok A. Seroepidemiology of Burkholderia pseudomallei, Etiologic Agent of Melioidosis, in the Ouest and Sud-Est Departments of Haiti. Am J Trop Med Hyg 2018; 99:1222-1228. [PMID: 30226137 PMCID: PMC6221251 DOI: 10.4269/ajtmh.18-0352] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2018] [Accepted: 08/22/2018] [Indexed: 12/13/2022] Open
Abstract
Burkholderia pseudomallei, the etiological agent of melioidosis, has been hypothesized to be endemic throughout the Caribbean, including the impoverished nation of Haiti. However, because of the protean clinical manifestations, presence of asymptomatic infections, and limited medical diagnostic capacity, the identification of active melioidosis cases remains challenging. A seroepidemiological study was conducted using a novel enzyme-linked immunosorbent assay (ELISA) to detect antibodies toward B. pseudomallei in the native population. The performance of an indirect ELISA with purified lipopolysaccharide (LPS) from B. pseudomallei was evaluated using serum collected from rhesus macaques exposed to aerosolized B. pseudomallei. After optimization, serum collected from asymptomatic population members (n = 756) was screened for polyvalent (immunoglobulin M [IgM]/ immunoglobulin G [IgG]/ immunoglobulin A) and monoclonal (IgG or IgM) immunoglobulins against B. pseudomallei LPS. The population seroprevalence was 11.5% (95% confidence interval [CI]: 9.2, 13.8) for polyvalent immunoglobulins, 9.8% (95% CI: 7.7, 11.9) for IgG, and 1.7% (95% CI: 0.8, 2.6%) for IgM. The seroprevalence was not significantly different by gender (P = 0.16), but increased significantly (P < 0.001) with age, yielding an estimated annual seroconversion rate of 1.05% (95% CI: 0.81, 1.3). The detection of both recent (IgM+) and previous (IgG+) exposure to B. pseudomallei provides serological evidence that melioidosis is endemic in Haiti.
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Affiliation(s)
- Thomas A. Weppelmann
- Herbert Wertheim College of Medicine, Florida International University, Miami, Florida
- Emerging Pathogens Institute, University of Florida, Gainesville, Florida
| | - Michael H. Norris
- Emerging Pathogens Institute, University of Florida, Gainesville, Florida
- Department of Infectious Diseases and Immunology, College of Veterinary Medicine, University of Florida, Gainesville, Florida
| | | | - Md. Siddiqur Rahman Khan
- Emerging Pathogens Institute, University of Florida, Gainesville, Florida
- Department of Infectious Diseases and Immunology, College of Veterinary Medicine, University of Florida, Gainesville, Florida
| | - Bernard A. Okech
- Emerging Pathogens Institute, University of Florida, Gainesville, Florida
- Department of Environmental and Global Health, College of Public Health and Health Professions, University of Florida, Gainesville, Florida
| | - Anthony P. Cannella
- Emerging Pathogens Institute, University of Florida, Gainesville, Florida
- Department of Medicine, College of Medicine, University of Florida, Gainesville, Florida
| | - Herbert P. Schweizer
- Emerging Pathogens Institute, University of Florida, Gainesville, Florida
- Department of Molecular Genetics and Microbiology, College of Medicine, University of Florida, Gainesville, Florida
| | | | - Apichai Tuanyok
- Emerging Pathogens Institute, University of Florida, Gainesville, Florida
- Department of Infectious Diseases and Immunology, College of Veterinary Medicine, University of Florida, Gainesville, Florida
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Lipid A Remodeling Is a Pathoadaptive Mechanism That Impacts Lipopolysaccharide Recognition and Intracellular Survival of Burkholderia pseudomallei. Infect Immun 2018; 86:IAI.00360-18. [PMID: 30037795 PMCID: PMC6204721 DOI: 10.1128/iai.00360-18] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2018] [Accepted: 07/13/2018] [Indexed: 12/13/2022] Open
Abstract
Burkholderia pseudomallei causes the severe disease melioidosis. The bacterium subverts the host immune system and replicates inside cells, and host mortality results primarily from sepsis-related complications. Burkholderia pseudomallei causes the severe disease melioidosis. The bacterium subverts the host immune system and replicates inside cells, and host mortality results primarily from sepsis-related complications. Lipopolysaccharide (LPS) is a major virulence factor and mediator of sepsis that many pathogens capable of intracellular growth modify to reduce their immunological “footprint.” The binding strength of B. pseudomallei LPS for human LPS binding protein (hLBP) was measured using surface plasmon resonance. The structures of lipid A isolated from B. pseudomallei under different temperatures were analyzed by matrix-assisted laser desorption ionization–time of flight mass spectrometry (MALDI-TOF MS), and the gene expression of two lipid A remodeling genes, lpxO and pagL, was investigated. The LPS was characterized for its ability to trigger tumor necrosis factor alpha (TNF-α) release and to activate caspase-11-triggered pyroptosis by introduction of LPS into the cytosol. Lipid A from long-term chronic-infection isolates was isolated and characterized by MALDI-TOF MS and also by the ability to trigger caspase-11-mediated cell death. Lipid A from B. pseudomallei 1026b lpxO and pagL mutants were characterized by positive- and negative-mode MALDI-TOF MS to ultimately identify their role in lipid A structural modifications. Replication of lpxO and pagL mutants and their complements within macrophages showed that lipid A remodeling can effect growth in host cells and activation of caspase-11-mediated cytotoxicity.
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Webb JR, Price EP, Somprasong N, Schweizer HP, Baird RW, Currie BJ, Sarovich DS. Development and validation of a triplex quantitative real-time PCR assay to detect efflux pump-mediated antibiotic resistance in Burkholderia pseudomallei. Future Microbiol 2018; 13:1403-1418. [PMID: 30256166 PMCID: PMC6190177 DOI: 10.2217/fmb-2018-0155] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2018] [Accepted: 07/23/2018] [Indexed: 01/12/2023] Open
Abstract
AIM To develop a probe-based triplex quantitative real-time PCR assay to simultaneously detect the upregulation of the efflux pumps AmrAB-OprA, BpeAB-OprB and BpeEF-OprC in Burkholderia pseudomallei strains exhibiting increased minimum inhibitory concentrations toward meropenem, doxycycline or trimethoprim-sulfamethoxazole. METHODS The triplex assay was developed and subsequently tested on RNA isolated from eight clinical and eight laboratory-generated B. pseudomallei mutants harboring efflux pump regulator mutations. RESULTS The triplex assay accurately detected efflux pump upregulation in all clinical and laboratory mutants, which corresponded with decreased antibiotic susceptibility or antibiotic resistance. CONCLUSION Rapid detection of antibiotic resistance provides clinicians with a tool to identify potential treatment failure in near real time, enabling informed alteration of treatment during an infection and improved patient outcomes.
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Affiliation(s)
- Jessica R Webb
- Global & Tropical Health Division, Menzies School of Health Research, Darwin, Northern Territory, Australia
| | - Erin P Price
- Global & Tropical Health Division, Menzies School of Health Research, Darwin, Northern Territory, Australia
- Faculty of Science, Health, Education & Engineering, University of the Sunshine Coast, Sippy Downs, Queensland, Australia
| | - Nawarat Somprasong
- Department of Molecular Genetics & Microbiology, College of Medicine, Emerging Pathogens Institute, University of Florida, Gainesville, FL, USA
| | - Herbert P Schweizer
- Department of Molecular Genetics & Microbiology, College of Medicine, Emerging Pathogens Institute, University of Florida, Gainesville, FL, USA
| | - Robert W Baird
- Departments of Infectious Diseases & Pathology & Northern Territory Medical Program, Royal Darwin Hospital, Darwin, Northern Territory, Australia
| | - Bart J Currie
- Global & Tropical Health Division, Menzies School of Health Research, Darwin, Northern Territory, Australia
- Departments of Infectious Diseases & Pathology & Northern Territory Medical Program, Royal Darwin Hospital, Darwin, Northern Territory, Australia
| | - Derek S Sarovich
- Global & Tropical Health Division, Menzies School of Health Research, Darwin, Northern Territory, Australia
- Faculty of Science, Health, Education & Engineering, University of the Sunshine Coast, Sippy Downs, Queensland, Australia
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Rhodes KA, Somprasong N, Podnecky NL, Mima T, Chirakul S, Schweizer HP. Molecular determinants of Burkholderia pseudomallei BpeEF-OprC efflux pump expression. MICROBIOLOGY-SGM 2018; 164:1156-1167. [PMID: 30024368 DOI: 10.1099/mic.0.000691] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Burkholderia pseudomallei, the cause of melioidosis, is intrinsically resistant to many antibiotics. Acquired multidrug resistance, including resistance to doxycycline and co-trimoxazole used for melioidosis eradication phase therapy, is mainly attributed to constitutive expression of the BpeEF-OprC efflux pump. Constitutive expression of this pump is caused by mutations affecting two highly similar LysR-type transcriptional regulators (LTTR), BpeT and BpeS, but their interaction with the regulatory region governing BpeEF-OprC expression has not yet been studied. The bpeE-bpeF-oprC genes are distally located in the llpE-bpeE-bpeF-oprC operon. The llpE gene encodes a putative lipase/esterase of unknown function. We show that in a bpeT mutant llpE is constitutively co-transcribed with bpeE-bpeF-oprC. As expected from previous studies with B. cenocepacia, deletion of llpE does not affect antibiotic efflux. Using transcriptional bpeE'-lacZ fusions, we demonstrate that the 188 bp bpeT-llpE intergenic region located between bpeT and the llpE-bpeE-bpeF-oprC operon contains regulatory elements needed for control of bpeT and llpE-bpeE-bpeF-oprC operon expression. By native polyacrylamide gel electrophoresis and electrophoretic mobility shift assays with purified recombinant BpeT and BpeS proteins, we show BpeT and BpeS form oligomers that share a 14 bp binding site overlapping the essential region required for llpE-bpeE-bpeF-oprC expression. The binding site contains the conserved T-N11-A LTTR box motif involved in binding of LysR proteins, which in concert with two other possible LTTR boxes may mediate BpeT and BpeS regulation of BpeEF-OprC expression. These studies form the basis for further investigation of BpeEF-OprC expression and regulation at the molecular level by yet unknown external stimuli.
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Affiliation(s)
- Katherine A Rhodes
- 1Department of Microbiology, Immunology and Pathology, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, CO, USA.,3Emerging Pathogens Institute, University of Florida, Gainesville, FL, USA.,2Department of Molecular Genetics and Microbiology, College of Medicine, Emerging Pathogens Institute, University of Florida, Gainesville, FL, USA.,†Present address: University of Arizona BIO5 Institute, Tucson, AZ 85721, USA
| | - Nawarat Somprasong
- 1Department of Microbiology, Immunology and Pathology, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, CO, USA.,2Department of Molecular Genetics and Microbiology, College of Medicine, Emerging Pathogens Institute, University of Florida, Gainesville, FL, USA.,3Emerging Pathogens Institute, University of Florida, Gainesville, FL, USA
| | - Nicole L Podnecky
- 1Department of Microbiology, Immunology and Pathology, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, CO, USA.,‡Present address: Department of Pharmacy, Faculty of Health Sciences, UiT - The Arctic University of Tromsø, 9037 Tromsø, Norway
| | - Takehiko Mima
- 1Department of Microbiology, Immunology and Pathology, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, CO, USA.,§Present address: Department of Bacteriology, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, 2-5-1 Shikata-cho, Kita-ku, Okayama, 700-8558, Japan
| | - Sunisa Chirakul
- 2Department of Molecular Genetics and Microbiology, College of Medicine, Emerging Pathogens Institute, University of Florida, Gainesville, FL, USA.,3Emerging Pathogens Institute, University of Florida, Gainesville, FL, USA
| | - Herbert P Schweizer
- 3Emerging Pathogens Institute, University of Florida, Gainesville, FL, USA.,2Department of Molecular Genetics and Microbiology, College of Medicine, Emerging Pathogens Institute, University of Florida, Gainesville, FL, USA.,1Department of Microbiology, Immunology and Pathology, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, CO, USA
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Chirakul S, Norris MH, Pagdepanichkit S, Somprasong N, Randall LB, Shirley JF, Borlee BR, Lomovskaya O, Tuanyok A, Schweizer HP. Transcriptional and post-transcriptional regulation of PenA β-lactamase in acquired Burkholderia pseudomallei β-lactam resistance. Sci Rep 2018; 8:10652. [PMID: 30006637 PMCID: PMC6045580 DOI: 10.1038/s41598-018-28843-7] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2018] [Accepted: 07/01/2018] [Indexed: 01/15/2023] Open
Abstract
Therapy of Burkholderia pseudomallei acute infections is largely limited to a few β-lactam antibiotics such as ceftazidime or meropenem. Although relatively rare, resistance emergence during therapy leads to treatment failures with high mortality rates. In the absence of acquired external resistance determinants in B. pseudomallei emergence of β-lactam resistance is invariably caused by mutational modification of genomically encoded factors. These include the deletion of the ceftazidime target penicillin-binding protein 3 or amino acid changes in the Class A PenA β-lactamase that expand its substrate spectrum, as well as penA gene duplication and amplification or its overexpression via transcriptional up-regulation. Evidence is presented that penA is co-transcribed with the upstream nlpD1 gene, that the transcriptional terminator for nlpD1 serves as a penA attenuator and that generation of a new promoter immediately upstream of the terminator/attenuator by a conserved G to A transition leads to anti-termination and thus constitutive PenA expression and extended β-lactam resistance. Further evidence obtained with the extensively β-lactam resistant clinical isolate Bp1651 shows that in addition to PenA overexpression and structural mutations other adaptive mechanisms contribute to intrinsic and acquired B. pseudomallei β-lactam resistance.
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Affiliation(s)
- Sunisa Chirakul
- University of Florida, College of Medicine, Emerging Pathogens Institute, Department of Molecular Genetics and Microbiology, Gainesville, FL, 32610, USA
| | - Michael H Norris
- University of Florida, College of Veterinary Medicine, Emerging Pathogens Institute, Department of Infectious Diseases and Immunity, Gainesville, FL, 32610, USA
| | - Sirawit Pagdepanichkit
- University of Florida, College of Medicine, Emerging Pathogens Institute, Department of Molecular Genetics and Microbiology, Gainesville, FL, 32610, USA
- Chulalongkorn University, Faculty of Veterinary Science, Department of Veterinary Public Health, Research Unit in Microbial Food Safety and Antimicrobial Resistance, Bangkok, 10330, Thailand
| | - Nawarat Somprasong
- University of Florida, College of Medicine, Emerging Pathogens Institute, Department of Molecular Genetics and Microbiology, Gainesville, FL, 32610, USA
| | - Linnell B Randall
- University of Florida, College of Medicine, Emerging Pathogens Institute, Department of Molecular Genetics and Microbiology, Gainesville, FL, 32610, USA
- Cornell University, Boyd Thompson Institute, Ithaca, NY, 14853, USA
| | - James F Shirley
- University of Florida, College of Medicine, Emerging Pathogens Institute, Department of Molecular Genetics and Microbiology, Gainesville, FL, 32610, USA
| | - Bradley R Borlee
- Colorado State University, College of Veterinary Medicine and Biomedical Sciences, Department of Microbiology, Immunology and Pathology, Fort Collins, CO, 80523, USA
| | | | - Apichai Tuanyok
- University of Florida, College of Veterinary Medicine, Emerging Pathogens Institute, Department of Infectious Diseases and Immunity, Gainesville, FL, 32610, USA
| | - Herbert P Schweizer
- University of Florida, College of Medicine, Emerging Pathogens Institute, Department of Molecular Genetics and Microbiology, Gainesville, FL, 32610, USA.
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Malleilactone Is a Burkholderia pseudomallei Virulence Factor Regulated by Antibiotics and Quorum Sensing. J Bacteriol 2018; 200:JB.00008-18. [PMID: 29735757 DOI: 10.1128/jb.00008-18] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2018] [Accepted: 04/30/2018] [Indexed: 12/21/2022] Open
Abstract
Burkholderia pseudomallei, the causative agent of melioidosis, encodes almost a dozen predicted polyketide (PK) biosynthetic gene clusters. Many of these are regulated by LuxR-I-type acyl-homoserine (AHL) quorum-sensing systems. One of the PK gene clusters, the mal gene cluster, is conserved in the close relative Burkholderia thailandensis The B. thailandensis mal genes code for the cytotoxin malleilactone and are regulated by a genetically linked LuxR-type transcription factor, MalR. Although AHLs typically interact with LuxR-type proteins to modulate gene transcription, the B. thailandensis MalR does not appear to be an AHL receptor. Here, we characterize the mal genes and MalR in B. pseudomallei We use chemical analyses to demonstrate that the B. pseudomallei mal genes code for malleilactone. Our results show that MalR and the mal genes contribute to the ability of B. pseudomallei to kill Caenorhabditis elegans In B. thailandensis, antibiotics like trimethoprim can activate MalR by driving transcription of the mal genes, and we demonstrate that some of the same antibiotics induce expression of B. pseudomallei malR We also demonstrate that B. pseudomallei MalR does not respond directly to AHLs. Our results suggest that MalR is indirectly repressed by AHLs, possibly through a repressor, ScmR. We further show that malleilactone is a B. pseudomallei virulence factor and provide the foundation for understanding how malleilactone contributes to the pathology of melioidosis infections.IMPORTANCE Many bacterially produced polyketides are cytotoxic to mammalian cells and are potentially important contributors to pathogenesis during infection. We are interested in the polyketide gene clusters present in Burkholderia pseudomallei, which causes the often-fatal human disease melioidosis. Using knowledge gained by studies in the close relative Burkholderia thailandensis, we show that one of the B. pseudomallei polyketide biosynthetic clusters produces a cytotoxic polyketide, malleilactone. Malleilactone contributes to B. pseudomallei virulence in a Caenorhabditis elegans infection model and is regulated by an orphan LuxR family quorum-sensing transcription factor, MalR. Our studies demonstrate that malleilactone biosynthesis or MalR could be new targets for developing therapeutics to treat melioidosis.
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Kraft CE, Angert ER. Competition for vitamin B1 (thiamin) structures numerous ecological interactions. QUARTERLY REVIEW OF BIOLOGY 2018; 92:151-68. [PMID: 29562121 DOI: 10.1086/692168] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
Thiamin (vitamin B1) is a cofactor required for essential biochemical reactions in all living organisms, yet free thiamin is scarce in the environment. The diversity of biochemical pathways involved in the acquisition, degradation, and synthesis of thiamin indicates that organisms have evolved numerous ecological strategies for meeting this nutritional requirement. In this review we synthesize information from multiple disciplines to show how the complex biochemistry of thiamin influences ecological outcomes of interactions between organisms in environments ranging from the open ocean and the Australian outback to the gastrointestinal tract of animals. We highlight population and ecosystem responses to the availability or absence of thiamin. These include widespread mortality of fishes, birds, and mammals, as well as the thiamin-dependent regulation of ocean productivity. Overall, we portray thiamin biochemistry as the foundation for molecularly mediated ecological interactions that influence survival and abundance of a vast array of organisms.
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Determinants of Extreme β-Lactam Tolerance in the Burkholderia pseudomallei Complex. Antimicrob Agents Chemother 2018; 62:AAC.00068-18. [PMID: 29439964 DOI: 10.1128/aac.00068-18] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2018] [Accepted: 02/04/2018] [Indexed: 12/22/2022] Open
Abstract
Slow-growing bacteria are insensitive to killing by antibiotics, a trait known as antibiotic tolerance. In this study, we characterized the genetic basis of an unusually robust β-lactam (meropenem) tolerance seen in Burkholderia species. We identified tolerance genes under three different slow-growth conditions by extensive transposon mutant sequencing (Tn-seq), followed by single mutant validation. There were three principal findings. First, mutations in a small number of genes reduced tolerance under multiple conditions. Most of the functions appeared to be specific to peptidoglycan synthesis and the response to its disruption by meropenem action rather than being associated with more general physiological processes. The top tolerance genes are involved in immunity toward a type VI toxin targeting peptidoglycan (BTH_I0069), peptidoglycan recycling (ldcA), periplasmic regulation by proteolysis (prc), and an envelope stress response (rpoE and degS). Second, most of the tolerance functions did not contribute to growth in the presence of meropenem (intrinsic resistance), indicating that the two traits are largely distinct. Third, orthologues of many of the top Burkholderia thailandensis tolerance genes were also important in Burkholderia pseudomallei Overall, these studies show that the determinants of meropenem tolerance differ considerably depending on cultivation conditions, but that there are a few shared functions with strong mutant phenotypes that are important in multiple Burkholderia species.
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Norris MH, Khan MSR, Chirakul S, Schweizer HP, Tuanyok A. Outer Membrane Vesicle Vaccines from Biosafe Surrogates Prevent Acute Lethal Glanders in Mice. Vaccines (Basel) 2018; 6:E5. [PMID: 29320408 PMCID: PMC5874646 DOI: 10.3390/vaccines6010005] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2017] [Revised: 01/04/2018] [Accepted: 01/06/2018] [Indexed: 01/13/2023] Open
Abstract
Burkholderia mallei is a host-adapted Gram-negative mammalian pathogen that causes the severe disease glanders. Glanders can manifest as a rapid acute progression or a chronic debilitating syndrome primarily affecting solipeds and humans in close association with infected animals. In USA, B. mallei is classified as one of the most important bacterial biothreat agents. Presently, there is no licensed glanders vaccine available for humans or animals. In this work, outer membrane vesicles (OMVs) were isolated from three attenuated biosafe bacterial strains, Burkholderia pseudomallei Bp82, B. thailandensis E555, and B. thailandensis TxDOH and used to vaccinate mice. B. thailandensis OMVs induced significantly higher antibody responses that were investigated. B. mallei specific serum antibody responses were of higher magnitude in mice vaccinated with B. thailandensis OMVs compared to levels in mice vaccinated with B. pseudomallei OMVs. OMVs derived from biosafe strains protected mice from acute lethal glanders with vesicles from the two B. thailandensis strains affording significant protection (>90%) up to 35 days post-infection with some up to 60 days. Organ loads from 35-day survivors indicated bacteria colonization of the lungs, liver, and spleen while those from 60 days had high CFUs in the spleens. The highest antibody producing vaccine (B. thailandensis E555 OMVs) also protected C57BL/6 mice from acute inhalational glanders with evidence of full protection.
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Affiliation(s)
- Michael H Norris
- Department of Infectious Diseases and Immunology, College of Veterinary Medicine; University of Florida, Gainesville, FL 32608, USA.
- Emerging Pathogens Institute, University of Florida, Gainesville, FL 32610, USA.
| | - Mohammad S R Khan
- Department of Infectious Diseases and Immunology, College of Veterinary Medicine; University of Florida, Gainesville, FL 32608, USA.
- Emerging Pathogens Institute, University of Florida, Gainesville, FL 32610, USA.
| | - Sunisa Chirakul
- Department of Infectious Diseases and Immunology, College of Veterinary Medicine; University of Florida, Gainesville, FL 32608, USA.
- Emerging Pathogens Institute, University of Florida, Gainesville, FL 32610, USA.
| | - Herbert P Schweizer
- Emerging Pathogens Institute, University of Florida, Gainesville, FL 32610, USA.
- Department of Molecular Genetics and Microbiology, College of Medicine, University of Florida, Gainesville, FL 32603, USA.
| | - Apichai Tuanyok
- Department of Infectious Diseases and Immunology, College of Veterinary Medicine; University of Florida, Gainesville, FL 32608, USA.
- Emerging Pathogens Institute, University of Florida, Gainesville, FL 32610, USA.
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Haynes MK, Garcia M, Peters R, Waller A, Tedesco P, Ursu O, Bologa CG, Santos RG, Pinilla C, Wu TH, Lovchik JA, Oprea TI, Sklar LA, Tegos GP. High-Throughput Flow Cytometry Screening of Multidrug Efflux Systems. Methods Mol Biol 2018; 1700:293-318. [PMID: 29177837 DOI: 10.1007/978-1-4939-7454-2_16] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
The resistance nodulation cell division (RND) family of proteins are inner membrane transporters that associate with periplasmic adaptor proteins and outer membrane porins to affect substrate transport from the cytosol and periplasm in Gram-negative bacteria. Various structurally diverse compounds are substrates of RND transporters. Along with their notable role in antibiotic resistance, these transporters are essential for niche colonization, quorum sensing, and virulence as well as for the removal of fatty acids and bile salts. As such, RNDs are an attractive target for antimicrobial development. However, while enhancing the utility of antibiotics with an RND inhibitor is an appealing concept, only a small core of chemotypes has been identified as efflux pump inhibitors (EPIs). Thus, our key objective is the development and validation of an efflux profiling and discovery strategy for RND model systems. Here we describe a flow cytometric dye accumulation assay that uses fluorescein diacetate (FDA) to interrogate the model Gram-negative pathogens Escherichia coli, Franscisella tularensis, and Burkholderia pseudomallei. Fluorochrome retention is increased in the presence of known efflux inhibitors and in RND deletion strains. The assay can be used in a high-throughput format to evaluate efflux of dye-substrate candidates and to screen chemical libraries for novel EPIs. Triaged compounds that inhibit efflux in pathogenic strains are tested for growth inhibition and antibiotic potentiation using microdilution culture plates in a select agent Biosafety Level-3 (BSL3) environment. This combined approach demonstrates the utility of flow cytometric analysis for efflux activity and provides a useful platform in which to characterize efflux in pathogenic Gram-negative bacteria. Screening small molecule libraries for novel EPI candidates offers the potential for the discovery of new classes of antibacterial compounds.
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Affiliation(s)
- Mark K Haynes
- Center for Molecular Discovery, University of New Mexico School of Medicine, Albuquerque, NM, USA.
- Department of Pathology, University of New Mexico School of Medicine, Albuquerque, NM, USA.
| | - Matthew Garcia
- Center for Molecular Discovery, University of New Mexico School of Medicine, Albuquerque, NM, USA
- Department of Pathology, University of New Mexico School of Medicine, Albuquerque, NM, USA
| | - Ryan Peters
- Center for Infectious Disease and Immunity, Department of Internal Medicine, University of New Mexico School of Medicine, Albuquerque, NM, USA
| | - Anna Waller
- Center for Molecular Discovery, University of New Mexico School of Medicine, Albuquerque, NM, USA
- Department of Pathology, University of New Mexico School of Medicine, Albuquerque, NM, USA
| | - Pietro Tedesco
- Institute of Protein Biochemistry, National Research Council, Naples, Italy
- Department of Chemical Sciences and School of Biotechnological Sciences, University of Naples, Naples, Italy
| | - Oleg Ursu
- Division of Translational Informatics, Department of Internal Medicine, University of New Mexico School of Medicine, Albuquerque, NM, USA
| | - Cristian G Bologa
- Division of Translational Informatics, Department of Internal Medicine, University of New Mexico School of Medicine, Albuquerque, NM, USA
| | - Radleigh G Santos
- Torrey Pines Institute for Molecular Studies, Port St Lucie, FL, USA
| | | | - Terry H Wu
- Center for Infectious Disease and Immunity, Department of Internal Medicine, University of New Mexico School of Medicine, Albuquerque, NM, USA
| | - Julie A Lovchik
- Center for Infectious Disease and Immunity, Department of Internal Medicine, University of New Mexico School of Medicine, Albuquerque, NM, USA
| | - Tudor I Oprea
- Division of Translational Informatics, Department of Internal Medicine, University of New Mexico School of Medicine, Albuquerque, NM, USA
| | - Larry A Sklar
- Center for Molecular Discovery, University of New Mexico School of Medicine, Albuquerque, NM, USA
- Department of Pathology, University of New Mexico School of Medicine, Albuquerque, NM, USA
| | - George P Tegos
- Department of Dermatology, Harvard Medical School, Boston, MA, USA.
- Wellman Center for Photomedicine, Massachusetts General Hospital, Boston, MA, USA.
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A Burkholderia pseudomallei Outer Membrane Vesicle Vaccine Provides Cross Protection against Inhalational Glanders in Mice and Non-Human Primates. Vaccines (Basel) 2017; 5:vaccines5040049. [PMID: 29232837 PMCID: PMC5748615 DOI: 10.3390/vaccines5040049] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2017] [Revised: 12/05/2017] [Accepted: 12/06/2017] [Indexed: 01/28/2023] Open
Abstract
Burkholderia mallei is a Gram-negative, non-motile, facultative intracellular bacillus and the causative agent of glanders, a highly contagious zoonotic disease. B. mallei is naturally resistant to multiple antibiotics and there is concern for its potential use as a bioweapon, making the development of a vaccine against B. mallei of critical importance. We have previously demonstrated that immunization with multivalent outer membrane vesicles (OMV) derived from B. pseudomallei provide significant protection against pneumonic melioidosis. Given that many virulence determinants are highly conserved between the two species, we sought to determine if the B. pseudomallei OMV vaccine could cross-protect against B. mallei. We immunized C57Bl/6 mice and rhesus macaques with B. pseudomallei OMVs and subsequently challenged animals with aerosolized B. mallei. Immunization with B. pseudomallei OMVs significantly protected mice against B. mallei and the protection observed was comparable to that achieved with a live attenuated vaccine. OMV immunization induced the production of B.mallei-specific serum IgG and a mixed Th1/Th17 CD4 and CD8 T cell response in mice. Additionally, immunization of rhesus macaques with B. pseudomallei OMVs provided protection against glanders and induced B.mallei-specific serum IgG in non-human primates. These results demonstrate the ability of the multivalent OMV vaccine platform to elicit cross-protection against closely-related intracellular pathogens and to induce robust humoral and cellular immune responses against shared protective antigens.
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Titball RW, Burtnick MN, Bancroft GJ, Brett P. Burkholderia pseudomallei and Burkholderia mallei vaccines: Are we close to clinical trials? Vaccine 2017; 35:5981-5989. [DOI: 10.1016/j.vaccine.2017.03.022] [Citation(s) in RCA: 52] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2017] [Revised: 02/17/2017] [Accepted: 03/07/2017] [Indexed: 10/19/2022]
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Mechanisms of Resistance to Folate Pathway Inhibitors in Burkholderia pseudomallei: Deviation from the Norm. mBio 2017; 8:mBio.01357-17. [PMID: 28874476 PMCID: PMC5587915 DOI: 10.1128/mbio.01357-17] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
The trimethoprim and sulfamethoxazole combination, co-trimoxazole, plays a vital role in the treatment of Burkholderia pseudomallei infections. Previous studies demonstrated that the B. pseudomallei BpeEF-OprC efflux pump confers widespread trimethoprim resistance in clinical and environmental isolates, but this is not accompanied by significant resistance to co-trimoxazole. Using the excluded select-agent strain B. pseudomallei Bp82, we now show that in vitro acquired trimethoprim versus co-trimoxazole resistance is mainly mediated by constitutive BpeEF-OprC expression due to bpeT mutations or by BpeEF-OprC overexpression due to bpeS mutations. Mutations in bpeT affect the carboxy-terminal effector-binding domain of the BpeT LysR-type activator protein. Trimethoprim resistance can also be mediated by dihydrofolate reductase (FolA) target mutations, but this occurs rarely unless BpeEF-OprC is absent. BpeS is a transcriptional regulator that is 62% identical to BpeT. Mutations affecting the BpeS DNA-binding or carboxy-terminal effector-binding domains result in constitutive BpeEF-OprC overexpression, leading to trimethoprim and sulfamethoxazole efflux and thus to co-trimoxazole resistance. The majority of laboratory-selected co-trimoxazole-resistant mutants often also contain mutations in folM, encoding a pterin reductase. Genetic analyses of these mutants established that both bpeS mutations and folM mutations contribute to co-trimoxazole resistance, although the exact role of folM remains to be determined. Mutations affecting bpeT, bpeS, and folM are common in co-trimoxazole-resistant clinical isolates, indicating that mutations affecting these genes are clinically significant. Co-trimoxazole resistance in B. pseudomallei is a complex phenomenon, which may explain why resistance to this drug is rare in this bacterium. Burkholderia pseudomallei causes melioidosis, a tropical disease that is difficult to treat. The bacterium’s resistance to antibiotics limits therapeutic options. The paucity of orally available drugs further complicates therapy. The oral drug of choice is co-trimoxazole, a combination of trimethoprim and sulfamethoxazole. These antibiotics target two distinct enzymes, FolA (dihydrofolate reductase) and FolP (dihydropteroate synthase), in the bacterial tetrahydrofolate biosynthetic pathway. Although co-trimoxazole resistance is minimized due to two-target inhibition, bacterial resistance due to folA and folP mutations does occur. Co-trimoxazole resistance in B. pseudomallei is rare and has not yet been studied. Co-trimoxazole resistance in this bacterium employs a novel strategy involving differential regulation of BpeEF-OprC efflux pump expression that determines the drug resistance profile. Contributing are mutations affecting folA, but not folP, and folM, a folate pathway-associated gene whose function is not yet well understood and which has not been previously implicated in folate inhibitor resistance in clinical isolates.
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Rapid Filter-Based Detection and Culture of Burkholderia pseudomallei from Small Volumes of Urine. J Clin Microbiol 2017. [PMID: 28637908 DOI: 10.1128/jcm.00764-17] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Clinical outcomes of melioidosis patients improve when the infecting agent, Burkholderia pseudomallei, is rapidly detected and identified by laboratory testing. Detection of B. pseudomallei DNA or recovery of the pathogen by culture from urine can support a diagnosis of melioidosis and guide patient care. Two new methods, designated filter-capture DNA isolation (FCDI) and filter cellular recovery (FCR), were developed to increase the sensitivity of detection and recovery of viable B. pseudomallei cells from small volumes (0.45 ml) of urine. DNA from eight strains of B. pseudomallei that were spiked into synthetic urine at low concentrations (1 × 102 CFU/ml) was detected in FCDI cell lysates using real-time PCR with greater consistency than with preparations from a QIAamp DNA Blood minikit. The FCR method showed greater B. pseudomallei detection sensitivity than conventional urine culture methods and resulted in typical colony growth at 24 h from as few as 1 × 102 CFU/ml. In addition, the FCR method does not rely on precipitation of a urine pellet by centrifugation and requires a smaller volume of urine. The FCDI and FCR methods described here could improve time-to-results and decrease the number of negative B. pseudomallei reports that are currently observed from urine culture as a consequence of samples containing low or variable bacterial cell concentrations.
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Norris MH, Rahman Khan MS, Schweizer HP, Tuanyok A. An avirulent Burkholderia pseudomallei ∆purM strain with atypical type B LPS: expansion of the toolkit for biosafe studies of melioidosis. BMC Microbiol 2017; 17:132. [PMID: 28592242 PMCID: PMC5461690 DOI: 10.1186/s12866-017-1040-4] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2017] [Accepted: 05/26/2017] [Indexed: 02/08/2023] Open
Abstract
BACKGROUND The work was undertaken to expand the tools available for researching Burkholderia pseudomallei (Bp), the etiological agent of the tropical disease melioidosis. Melioidosis has the potential to pose a severe threat to public health and safety. In the United States, Bp is listed as a Tier-1 select agent by the Centers for Disease Control and Prevention (CDC), thus requiring high levels of regulation and biosafety level 3 (BSL3) facilities for experimental manipulation of live organisms. An avirulent ∆purM derivative of strain 1026b (Bp82) has proven to be a valuable tool for biosafe research as a select-agent excluded strain, but the high level of genetic diversity between Bp strains necessitates an expansion of the biosafe toolset. RESULTS The ∆purM mutation was recapitulated in the Bp 576a strain, a serotype B background. An important difference between strains 1026b and 576a is the lipopolysaccharide (LPS), a major virulence factor and protective antigen. Polyclonal sera from 1026b-challenged non-human primates showed no cross reactivity with strain 576a LPS and low reactivity with whole cell lysate. Strain 576a replicates to higher levels in mouse organs and induces more TNF-α in the lungs of BALB/c mice compared to 1026b. The newly created Bp 576a ∆purM strain, designated 576mn, was auxotrophic for adenine in minimal media, capable of wild-type growth in rich media with addition of adenine, and auxotrophy was abrogated with single-copy complementation. Bp 576mn was unable to replicate in human cells and was avirulent in BALB/c mice following high-dose intranasal inoculation, similar to Bp82. Organ loads indicated a significant reduction in bacterial replication. CONCLUSIONS In this work, the new biosafe strain 576mn with atypical type B LPS was generated. This strain should prove a valuable addition to the toolkit for biosafe studies of Bp and development of therapeutic and preventative strategies aimed at combatting melioidosis. Strain 576mn is an ideal candidate for select-agent exclusion.
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Affiliation(s)
- Michael H Norris
- Department of Infectious Diseases and Pathology, College of Veterinary Medicine, Univeristy of Florida, Gainesville, FL, USA
- Emerging Pathogens Institute, University of Florida, Gainesville, FL, USA
| | - Md Siddiqur Rahman Khan
- Department of Infectious Diseases and Pathology, College of Veterinary Medicine, Univeristy of Florida, Gainesville, FL, USA
- Emerging Pathogens Institute, University of Florida, Gainesville, FL, USA
| | - Herbert P Schweizer
- Department of Molecular Genetics and Microbiology, College of Medicine, University of Florida, Gainesville, FL, USA
- Emerging Pathogens Institute, University of Florida, Gainesville, FL, USA
| | - Apichai Tuanyok
- Department of Infectious Diseases and Pathology, College of Veterinary Medicine, Univeristy of Florida, Gainesville, FL, USA.
- Emerging Pathogens Institute, University of Florida, Gainesville, FL, USA.
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Bugrysheva JV, Sue D, Gee JE, Elrod MG, Hoffmaster AR, Randall LB, Chirakul S, Tuanyok A, Schweizer HP, Weigel LM. Antibiotic Resistance Markers in Burkholderia pseudomallei Strain Bp1651 Identified by Genome Sequence Analysis. Antimicrob Agents Chemother 2017; 61:e00010-17. [PMID: 28396541 PMCID: PMC5444168 DOI: 10.1128/aac.00010-17] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2017] [Accepted: 03/31/2017] [Indexed: 12/30/2022] Open
Abstract
Burkholderia pseudomallei Bp1651 is resistant to several classes of antibiotics that are usually effective for treatment of melioidosis, including tetracyclines, sulfonamides, and β-lactams such as penicillins (amoxicillin-clavulanic acid), cephalosporins (ceftazidime), and carbapenems (imipenem and meropenem). We sequenced, assembled, and annotated the Bp1651 genome and analyzed the sequence using comparative genomic analyses with susceptible strains, keyword searches of the annotation, publicly available antimicrobial resistance prediction tools, and published reports. More than 100 genes in the Bp1651 sequence were identified as potentially contributing to antimicrobial resistance. Most notably, we identified three previously uncharacterized point mutations in penA, which codes for a class A β-lactamase and was previously implicated in resistance to β-lactam antibiotics. The mutations result in amino acid changes T147A, D240G, and V261I. When individually introduced into select agent-excluded B. pseudomallei strain Bp82, D240G was found to contribute to ceftazidime resistance and T147A contributed to amoxicillin-clavulanic acid and imipenem resistance. This study provides the first evidence that mutations in penA may alter susceptibility to carbapenems in B. pseudomallei Another mutation of interest was a point mutation affecting the dihydrofolate reductase gene folA, which likely explains the trimethoprim resistance of this strain. Bp1651 was susceptible to aminoglycosides likely because of a frameshift in the amrB gene, the transporter subunit of the AmrAB-OprA efflux pump. These findings expand the role of penA to include resistance to carbapenems and may assist in the development of molecular diagnostics that predict antimicrobial resistance and provide guidance for treatment of melioidosis.
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Affiliation(s)
| | - David Sue
- Centers for Disease Control and Prevention, Atlanta, Georgia, USA
| | - Jay E Gee
- Centers for Disease Control and Prevention, Atlanta, Georgia, USA
| | - Mindy G Elrod
- Centers for Disease Control and Prevention, Atlanta, Georgia, USA
| | | | - Linnell B Randall
- Department of Molecular Genetics and Microbiology, Emerging Pathogens Institute, University of Florida, Gainesville, Florida, USA
| | - Sunisa Chirakul
- Department of Molecular Genetics and Microbiology, Emerging Pathogens Institute, University of Florida, Gainesville, Florida, USA
| | - Apichai Tuanyok
- Department of Molecular Genetics and Microbiology, Emerging Pathogens Institute, University of Florida, Gainesville, Florida, USA
| | - Herbert P Schweizer
- Department of Molecular Genetics and Microbiology, Emerging Pathogens Institute, University of Florida, Gainesville, Florida, USA
| | - Linda M Weigel
- Centers for Disease Control and Prevention, Atlanta, Georgia, USA
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Immune Recognition of the Epidemic Cystic Fibrosis Pathogen Burkholderia dolosa. Infect Immun 2017; 85:IAI.00765-16. [PMID: 28348057 DOI: 10.1128/iai.00765-16] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2016] [Accepted: 03/20/2017] [Indexed: 12/31/2022] Open
Abstract
Burkholderia dolosa caused an outbreak in the cystic fibrosis (CF) clinic at Boston Children's Hospital from 1998 to 2005 and led to the infection of over 40 patients, many of whom died due to complications from infection by this organism. To assess whether B. dolosa significantly contributes to disease or is recognized by the host immune response, mice were infected with a sequenced outbreak B. dolosa strain, AU0158, and responses were compared to those to the well-studied CF pathogen Pseudomonas aeruginosa In parallel, mice were also infected with a polar flagellin mutant of B. dolosa to examine the role of flagella in B. dolosa lung colonization. The results showed a higher persistence in the host by B. dolosa strains, and yet, neutrophil recruitment and cytokine production were lower than those with P. aeruginosa The ability of host immune cells to recognize B. dolosa was then assessed, B. dolosa induced a robust cytokine response in cultured cells, and this effect was dependent on the flagella only when bacteria were dead. Together, these results suggest that B. dolosa can be recognized by host cells in vitro but may avoid or suppress the host immune response in vivo through unknown mechanisms. B. dolosa was then compared to other Burkholderia species and found to induce similar levels of cytokine production despite being internalized by macrophages more than Burkholderia cenocepacia strains. These data suggest that B. dolosa AU0158 may act differently with host cells and is recognized differently by immune systems than are other Burkholderia strains or species.
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Norris MH, Schweizer HP, Tuanyok A. Structural diversity of Burkholderia pseudomallei lipopolysaccharides affects innate immune signaling. PLoS Negl Trop Dis 2017; 11:e0005571. [PMID: 28453531 PMCID: PMC5425228 DOI: 10.1371/journal.pntd.0005571] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2017] [Revised: 05/10/2017] [Accepted: 04/17/2017] [Indexed: 12/21/2022] Open
Abstract
Burkholderia pseudomallei (Bp) causes the disease melioidosis. The main cause of mortality in this disease is septic shock triggered by the host responding to lipopolysaccharide (LPS) components of the Gram-negative outer membrane. Bp LPS is thought to be a weak inducer of the host immune system. LPS from several strains of Bp were purified and their ability to induce the inflammatory mediators TNF-α and iNOS in murine macrophages at low concentrations was investigated. Innate and adaptive immunity qPCR arrays were used to profile expression patterns of 84 gene targets in response to the different LPS types. Additional qPCR validation confirmed large differences in macrophage response. LPS from a high-virulence serotype B strain 576a and a virulent rough central nervous system tropic strain MSHR435 greatly induced the innate immune response indicating that the immunopathogenesis of these strains is different than in infections with strains similar to the prototype strain 1026b. The accumulation of autophagic vesicles was also increased in macrophages challenged with highly immunogenic Bp LPS. Gene induction and concomitant cytokine secretion profiles of human PBMCs in response to the various LPS were also investigated. MALDI-TOF/TOF was used to probe the lipid A portions of the LPS, indicating substantial structural differences that likely play a role in host response to LPS. These findings add to the evolving knowledge of host-response to bacterial LPS, which can be used to better understand septic shock in melioidosis patients and in the rational design of vaccines.
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Affiliation(s)
- Michael H. Norris
- Department of Infectious Diseases and Pathology, College of Veterinary Medicine, University of Florida, Gainesville, Florida, United States of America
- Emerging Pathogens Institute, University of Florida, Gainesville, Florida, United States of America
| | - Herbert P. Schweizer
- Emerging Pathogens Institute, University of Florida, Gainesville, Florida, United States of America
- Department of Molecular Genetics and Microbiology, College of Medicine, University of Florida, Gainesville, Florida, United States of America
| | - Apichai Tuanyok
- Department of Infectious Diseases and Pathology, College of Veterinary Medicine, University of Florida, Gainesville, Florida, United States of America
- Emerging Pathogens Institute, University of Florida, Gainesville, Florida, United States of America
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