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Brychcy M, Kokodynski A, Lloyd D, Godoy VG. AspFlex: Molecular Tools to Study Gene Expression and Regulation in Acinetobacter baumannii. ACS Synth Biol 2023; 12:2773-2777. [PMID: 37587063 PMCID: PMC10621034 DOI: 10.1021/acssynbio.3c00167] [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: 03/21/2023] [Indexed: 08/18/2023]
Abstract
Acinetobacter baumannii is a Gram-negative nosocomial opportunistic pathogen frequently found in hospital settings, causing high incidence of in-hospital infections. It belongs to the ESKAPE group of pathogens (the "A" stands for A. baumannii), which are known to easily develop antibiotic resistances. It is crucial to create a molecular toolkit to investigate its basic biology, such as gene regulation. Despite A. baumannii having been a threat for almost two decades, an efficient and high-throughput plasmid system that can replicate in A. baumannii has not yet been developed. This study adapts an existing toolkit for Escherichia coli to meet A. baumannii's unique requirements and expands it by constructing a plasmid-based CRISPR interference (CRISPRi) system to generate gene knockdowns in A. baumannii.
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Affiliation(s)
- Merlin Brychcy
- Biology Department, Northeastern University, Boston, Massachusetts 02115, United States
| | - Alexis Kokodynski
- Biology Department, Northeastern University, Boston, Massachusetts 02115, United States
| | - Devin Lloyd
- Biology Department, Northeastern University, Boston, Massachusetts 02115, United States
| | - Veronica G. Godoy
- Biology Department, Northeastern University, Boston, Massachusetts 02115, United States
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2
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de Dios R, Gadar K, McCarthy RR. A high-efficiency scar-free genome-editing toolkit for Acinetobacter baumannii. J Antimicrob Chemother 2022; 77:3390-3398. [PMID: 36216579 PMCID: PMC9704439 DOI: 10.1093/jac/dkac328] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2022] [Accepted: 09/05/2022] [Indexed: 12/14/2022] Open
Abstract
BACKGROUND The current mutagenesis tools for Acinetobacter baumannii leave selection markers or residual sequences behind, or involve tedious counterselection and screening steps. Furthermore, they are usually adapted for model strains, rather than for MDR clinical isolates. OBJECTIVES To develop a scar-free genome-editing tool suitable for chromosomal and plasmid modifications in MDR A. baumannii AB5075. METHODS We prove the efficiency of our adapted genome-editing system by deleting the multidrug efflux pumps craA, cmlA5 and resistance island 2 (RI2), as well as curing plasmid p1AB5075, and combining these mutations. We then characterized the susceptibility of the mutants compared with the WT to different antibiotics (i.e. chloramphenicol, amikacin and tobramycin) by disc diffusion assays and determined the MIC for each strain. RESULTS We successfully adapted the genome-editing protocol to A. baumannii AB5075, achieving a double recombination frequency close to 100% and routinely securing the construction of a mutant within 10 working days. Furthermore, we show that both CraA and p1AB5075 are involved in chloramphenicol resistance, and that RI2 and p1AB5075 play a role in resistance to amikacin and tobramycin. CONCLUSIONS We have developed a versatile and highly efficient genome-editing tool for A. baumannii. We have demonstrated it can be used to modify both the chromosome and native plasmids. By challenging the method, we show the role of CraA and p1AB5075 in antibiotic resistance.
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Affiliation(s)
- Rubén de Dios
- Division of Biosciences, Department of Life Sciences, Centre of Inflammation Research and Translational Medicine, College of Health and Life Sciences, Brunel University London, Uxbridge, UB8 3PH, UK
| | - Kavita Gadar
- Division of Biosciences, Department of Life Sciences, Centre of Inflammation Research and Translational Medicine, College of Health and Life Sciences, Brunel University London, Uxbridge, UB8 3PH, UK
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3
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The DdrR Coregulator of the Acinetobacter baumannii Mutagenic DNA Damage Response Potentiates UmuDAb Repression of Error-Prone Polymerases. J Bacteriol 2022; 204:e0016522. [PMID: 36194009 PMCID: PMC9664961 DOI: 10.1128/jb.00165-22] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Acinetobacter baumannii
is a nosocomial pathogen that acquires antibiotic resistance genes through conjugative transfer and carries out a robust mutagenic DNA damage response. After exposure to conditions typically encountered in health care settings, such as antibiotics, UV light, and desiccation, this species induces error-prone UmuD′
2
C polymerases.
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Dib K, El Banna A, Radulescu C, Lopez Campos G, Sheehan G, Kavanagh K. Histamine Produced by Gram-Negative Bacteria Impairs Neutrophil's Antimicrobial Response by Engaging the Histamine 2 Receptor. J Innate Immun 2022; 15:153-173. [PMID: 35858582 PMCID: PMC10643892 DOI: 10.1159/000525536] [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: 01/11/2022] [Accepted: 06/12/2022] [Indexed: 11/19/2022] Open
Abstract
We found that histamine (10-9 M) did not have any effect on the in vitro capture of Escherichia coli by neutrophils but accelerated its intracellular killing. In contrast, histamine (10-6 M) delayed the capture of Escherichia coli by neutrophils and reduced the amounts of pHrodo zymosan particles inside acidic mature phagosomes. Histamine acted through the H4R and the H2R, which are coupled to the Src family tyrosine kinases or the cAMP/protein kinase A pathway, respectively. The protein kinase A inhibitor H-89 abrogated the delay in bacterial capture induced by histamine (10-6 M) and the Src family tyrosine kinase inhibitor PP2 blocked histamine (10-9 M) induced acceleration of bacterial intracellular killing and tyrosine phosphorylation of proteins. To investigate the role of histamine in pathogenicity, we designed an Acinetobacter baumannii strain deficient in histamine production (hdc::TOPO). Galleria mellonella larvae inoculated with the wild-type Acinetobacter baumannii ATCC 17978 strain (1.1 × 105 CFU) died rapidly (100% death within 40 h) but not when inoculated with the Acinetobacter baumannii hdc::TOPO mutant (10% mortality). The concentration of histamine rose in the larval haemolymph upon inoculation of the wild type but not the Acinetobacter baumannii hdc::TOPO mutant, such concentration of histamine blocks the ability of hemocytes from Galleria mellonella to capture Candida albicans in vitro. Thus, bacteria-producing histamine, by maintaining high levels of histamine, may impair neutrophil phagocytosis by hijacking the H2R.
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Affiliation(s)
- Karim Dib
- Wellcome-Wolfson Institute for Experimental Medicine, Queen's University Belfast, Belfast, UK
| | - Amal El Banna
- Wellcome-Wolfson Institute for Experimental Medicine, Queen's University Belfast, Belfast, UK
| | - Clara Radulescu
- Wellcome-Wolfson Institute for Experimental Medicine, Queen's University Belfast, Belfast, UK
| | - Guillermo Lopez Campos
- Wellcome-Wolfson Institute for Experimental Medicine, Queen's University Belfast, Belfast, UK
| | - Gerard Sheehan
- Department of Biology, Maynooth University, Maynooth, Ireland
| | - Kevin Kavanagh
- Department of Biology, Maynooth University, Maynooth, Ireland
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5
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Polyphosphate Kinase Is Required for the Processes of Virulence and Persistence in Acinetobacter baumannii. Microbiol Spectr 2022; 10:e0123022. [PMID: 35867473 PMCID: PMC9430702 DOI: 10.1128/spectrum.01230-22] [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] [Indexed: 11/20/2022] Open
Abstract
Acinetobacter baumannii, one of the most successful bacteria causing severe nosocomial infection, was identified as a top-priority pathogen by the WHO. Thus, genetic manipulations to clarify the potential targets for fighting A. baumannii resistance and virulence are vital. Polyphosphate (polyP) kinase (PPK) is conserved in nearly all bacteria and is responsible for polyP formation, which is associated with bacterial pathogenicity and antibiotic resistance. In this study, ppk1-deficient (Δppk1::Apr), ppk1-complemented (Δppk1::Apr/PJL02-ppk1), and wild-type strains of A. baumannii ATCC 17978 were used to determine the influence of PPK1 on A. baumannii virulence and persistence mainly by polyP quantification, surface motility, biofilm formation, and bacterial persistence assays. Our work found that PPK1 is indispensable for polyP formation in vivo and that the motility of the PPK1-deficient strain was significantly impaired due to the lack of a pilus-like structure typically present compared with the complemented and wild-type strains. The deficiency of PPK1 also inhibited the biofilm formation of A. baumannii and decreased bacterial persistence under stimuli of high-concentration ampicillin (Amp) treatment, H2O2 stress, heat shock, and starvation stress. Furthermore, ppk1-deficient bacterium-infected mice showed a significantly reduced bacterial load and a decreased inflammatory response. However, complementation with PPK1 effectively rescued the impaired virulence and persistence of ppk1-deficient A. baumannii. In addition, metabonomic analysis revealed that PPK1 was associated with glycerophospholipid metabolism and fatty acid biosynthesis. Taken together, our results suggest that targeting PPK1 to control A. baumannii pathogenicity and persistence is a feasible strategy to fight this pathogen. IMPORTANCEA. baumannii was identified as a top-priority pathogen by the WHO due to its antibiotic resistance. Meanwhile, the pathogenicity of A. baumannii mediated by several vital virulence factors also cannot be ignored. Here, the role of PPK1 in A. baumannii was also explored. We found that the motility ability and biofilm formation of a PPK1-deficient strain were significantly impaired. Furthermore, PPK1 was essential for its persistence maintenance to resist stimuli of high-concentration Amp treatment, H2O2 stress, heat shock, and starvation stress. Metabonomic analysis revealed that PPK1 was associated with glycerophospholipid metabolism and fatty acid biosynthesis. In addition, ppk1-deficient bacterium-infected mice showed significantly reduced bacterial loads and a decreased inflammatory responses in vivo. Together, our results suggest that PPK1 is vital for A. baumannii pathogenicity and persistence.
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Fan Q, Bibi S, Vallad GE, Goss EM, Hurlbert JC, Paret ML, Jones JB, Timilsina S. Identification of Genes in Xanthomonas euvesicatoria pv. rosa That Are Host Limiting in Tomato. PLANTS 2022; 11:plants11060796. [PMID: 35336678 PMCID: PMC8951399 DOI: 10.3390/plants11060796] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/25/2022] [Revised: 02/24/2022] [Accepted: 03/02/2022] [Indexed: 11/30/2022]
Abstract
Xanthomonas euvesicatoria pv. rosa strain Xer07 causes a leaf spot on a Rosa sp. and is closely related to X. euvesicatoria pv. euvesicatoria (Xee) and X. perforans (Xp), causal agents of bacterial spot of tomato. However, Xer07 is not pathogenic on tomato and elicits a hypersensitive reaction (HR). We compared the genomes of the three bacterial species to identify the factors that limit Xer07 on tomato. Comparison of pathogenicity associated factors including the type III secretion systems identified two genes, xopA and xer3856, in Xer07 that have lower sequence homology in tomato pathogens. xer3856 is a homolog of genes in X. citri (xac3856) and X. fuscans pv. aurantifolii, both of which have been reported to elicit HRs in tomato. When xer3856 was expressed in X. perforans and infiltrated in tomato leaflets, the transconjugant elicited an HR and significantly reduced bacterial populations compared to the wildtype X. perforans strain. When xer3856 was mutated in Xer07, the mutant strain still triggered an HR in tomato leaflets. The second gene identified codes for type III secreted effector XopA, which contains a harpin domain that is distinct from the xopA homologs in Xee and Xp. The Xer07-xopA, when expressed in X. perforans, did not elicit an HR in tomato leaflets, but significantly reduced bacterial populations. This indicates that xopA and xer3856 genes in combination with an additional factor(s) limit Xer07 in tomato.
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Affiliation(s)
- Qiurong Fan
- Department of Plant Pathology, University of Florida, Gainesville, FL 32611, USA; (Q.F.); (S.B.); (G.E.V.); (E.M.G.); (M.L.P.)
| | - Shaheen Bibi
- Department of Plant Pathology, University of Florida, Gainesville, FL 32611, USA; (Q.F.); (S.B.); (G.E.V.); (E.M.G.); (M.L.P.)
| | - Gary E. Vallad
- Department of Plant Pathology, University of Florida, Gainesville, FL 32611, USA; (Q.F.); (S.B.); (G.E.V.); (E.M.G.); (M.L.P.)
- Gulf Coast Research and Education Center, University of Florida, Balm, FL 33598, USA
| | - Erica M. Goss
- Department of Plant Pathology, University of Florida, Gainesville, FL 32611, USA; (Q.F.); (S.B.); (G.E.V.); (E.M.G.); (M.L.P.)
- Emerging Pathogens Institute, University of Florida, Gainesville, FL 32610, USA
| | - Jason C. Hurlbert
- Department of Chemistry, Physics and Geology, Winthrop University, Rock Hill, SC 29733, USA;
| | - Matthews L. Paret
- Department of Plant Pathology, University of Florida, Gainesville, FL 32611, USA; (Q.F.); (S.B.); (G.E.V.); (E.M.G.); (M.L.P.)
- North Florida Research and Education Center, University of Florida, Quincy, FL 32351, USA
| | - Jeffrey B. Jones
- Department of Plant Pathology, University of Florida, Gainesville, FL 32611, USA; (Q.F.); (S.B.); (G.E.V.); (E.M.G.); (M.L.P.)
- Correspondence: (J.B.J.); (S.T.)
| | - Sujan Timilsina
- Department of Plant Pathology, University of Florida, Gainesville, FL 32611, USA; (Q.F.); (S.B.); (G.E.V.); (E.M.G.); (M.L.P.)
- Correspondence: (J.B.J.); (S.T.)
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7
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Toth M, Lee M, Stewart NK, Vakulenko SB. Effects of Inactivation of d,d-Transpeptidases of Acinetobacter baumannii on Bacterial Growth and Susceptibility to β-Lactam Antibiotics. Antimicrob Agents Chemother 2022; 66:e0172921. [PMID: 34780270 PMCID: PMC8765447 DOI: 10.1128/aac.01729-21] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2021] [Accepted: 11/12/2021] [Indexed: 11/20/2022] Open
Abstract
Resistance to β-lactams, the most used antibiotics worldwide, constitutes the major problem for the treatment of bacterial infections. In the nosocomial pathogen Acinetobacter baumannii, β-lactamase-mediated resistance to the carbapenem family of β-lactam antibiotics has resulted in the selection and dissemination of multidrug-resistant isolates, which often cause infections characterized by high mortality rates. There is thus an urgent demand for new β-lactamase-resistant antibiotics that also inhibit their targets, penicillin-binding proteins (PBPs). As some PBPs are indispensable for the biosynthesis of the bacterial cell wall and survival, we evaluated their importance for the growth of A. baumannii by performing gene inactivation studies of d,d-transpeptidase domains of high-molecular-mass (HMM) PBPs individually and in combination with one another. We show that PBP3 is essential for A. baumannii survival, as deletion mutants of this d,d-transpeptidase were not viable. The inactivation of PBP1a resulted in partial cell lysis and retardation of bacterial growth, and these effects were further enhanced by the additional inactivation of PBP2 but not PBP1b. Susceptibility to β-lactam antibiotics increased 4- to 8-fold for the A. baumannii PBP1a/PBP1b/PBP2 triple mutant and 2- to 4-fold for all remaining mutants. Analysis of the peptidoglycan structure revealed a significant change in the muropeptide composition of the triple mutant and demonstrated that the lack of d,d-transpeptidase activity of PBP1a, PBP1b, and PBP2 is compensated for by an increase in the l,d-transpeptidase-mediated cross-linking activity of LdtJ. Overall, our data showed that in addition to essential PBP3, the simultaneous inhibition of PBP1a and PBP2 or PBPs in combination with LdtJ could represent potential strategies for the design of novel drugs against A. baumannii.
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Affiliation(s)
- Marta Toth
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana, USA
| | - Mijoon Lee
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana, USA
- Mass Spectrometry and Proteomics Facility, University of Notre Dame, Notre Dame, Indiana, USA
| | - Nichole K. Stewart
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana, USA
| | - Sergei B. Vakulenko
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana, USA
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8
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Massier S, Robin B, Mégroz M, Wright A, Harper M, Hayes B, Cosette P, Broutin I, Boyce JD, Dé E, Hardouin J. Phosphorylation of Extracellular Proteins in Acinetobacter baumannii in Sessile Mode of Growth. Front Microbiol 2021; 12:738780. [PMID: 34659171 PMCID: PMC8517400 DOI: 10.3389/fmicb.2021.738780] [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: 07/09/2021] [Accepted: 08/30/2021] [Indexed: 11/21/2022] Open
Abstract
Acinetobacter baumannii is a problematic nosocomial pathogen owing to its increasing resistance to antibiotics and its great ability to survive in the hospital environment, which is linked to its capacity to form biofilms. Structural and functional investigations of post-translational modifications, such as phosphorylations, may lead to identification of candidates for therapeutic targets against this pathogen. Here, we present the first S/T/Y phosphosecretome of two A. baumannii strains, the reference strain ATCC 17978 and the virulent multi-drug resistant strain AB0057, cultured in two modes of growth (planktonic and biofilm) using TiO2 chromatography followed by high resolution mass spectrometry. In ATCC 17978, we detected a total of 137 (97 phosphoproteins) and 52 (33 phosphoproteins) phosphosites in biofilm and planktonic modes of growth, respectively. Similarly, in AB0057, 155 (119 phosphoproteins) and 102 (74 phosphoproteins) phosphosites in biofilm and planktonic modes of growth were identified, respectively. Both strains in the biofilm mode of growth showed a higher number of phosphosites and phosphoproteins compared to planktonic growth. Several phosphorylated sites are localized in key regions of proteins involved in either drug resistance (β-lactamases), adhesion to host tissues (pilins), or protein secretion (Hcp). Site-directed mutagenesis of the Hcp protein, essential for type VI secretion system-mediated interbacterial competition, showed that four of the modified residues are essential for type VI secretion system activity.
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Affiliation(s)
- Sébastien Massier
- Normandie Univ., UNIROUEN, INSA Rouen, CNRS, Polymers, Biopolymers, Surfaces Laboratory, Rouen, France
- PISSARO Proteomic Facility, IRIB, Mont-Saint-Aignan, France
| | - Brandon Robin
- Normandie Univ., UNIROUEN, INSA Rouen, CNRS, Polymers, Biopolymers, Surfaces Laboratory, Rouen, France
| | - Marianne Mégroz
- Infection and Immunity Program, Department of Microbiology, Monash Biomedicine Discovery Institute, Monash University, Melbourne, VIC, Australia
| | - Amy Wright
- Infection and Immunity Program, Department of Microbiology, Monash Biomedicine Discovery Institute, Monash University, Melbourne, VIC, Australia
| | - Marina Harper
- Infection and Immunity Program, Department of Microbiology, Monash Biomedicine Discovery Institute, Monash University, Melbourne, VIC, Australia
| | - Brooke Hayes
- Infection and Immunity Program, Department of Microbiology, Monash Biomedicine Discovery Institute, Monash University, Melbourne, VIC, Australia
| | - Pascal Cosette
- Normandie Univ., UNIROUEN, INSA Rouen, CNRS, Polymers, Biopolymers, Surfaces Laboratory, Rouen, France
- PISSARO Proteomic Facility, IRIB, Mont-Saint-Aignan, France
| | | | - John D. Boyce
- Infection and Immunity Program, Department of Microbiology, Monash Biomedicine Discovery Institute, Monash University, Melbourne, VIC, Australia
| | - Emmanuelle Dé
- Normandie Univ., UNIROUEN, INSA Rouen, CNRS, Polymers, Biopolymers, Surfaces Laboratory, Rouen, France
| | - Julie Hardouin
- Normandie Univ., UNIROUEN, INSA Rouen, CNRS, Polymers, Biopolymers, Surfaces Laboratory, Rouen, France
- PISSARO Proteomic Facility, IRIB, Mont-Saint-Aignan, France
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Short FL, Liu Q, Shah B, Clift HE, Naidu V, Li L, Prity FT, Mabbutt BC, Hassan KA, Paulsen IT. The Acinetobacter baumannii disinfectant resistance protein, AmvA, is a spermidine and spermine efflux pump. Commun Biol 2021; 4:1114. [PMID: 34552198 PMCID: PMC8458285 DOI: 10.1038/s42003-021-02629-6] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2020] [Accepted: 09/01/2021] [Indexed: 02/08/2023] Open
Abstract
Antimicrobial resistance genes, including multidrug efflux pumps, evolved long before the ubiquitous use of antimicrobials in medicine and infection control. Multidrug efflux pumps often transport metabolites, signals and host-derived molecules in addition to antibiotics or biocides. Understanding their ancestral physiological roles could inform the development of strategies to subvert their activity. In this study, we investigated the response of Acinetobacter baumannii to polyamines, a widespread, abundant class of amino acid-derived metabolites, which led us to identify long-chain polyamines as natural substrates of the disinfectant efflux pump AmvA. Loss of amvA dramatically reduced tolerance to long-chain polyamines, and these molecules induce expression of amvA through binding to its cognate regulator AmvR. A second clinically-important efflux pump, AdeABC, also contributed to polyamine tolerance. Our results suggest that the disinfectant resistance capability that allows A. baumannii to survive in hospitals may have evolutionary origins in the transport of polyamine metabolites.
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Affiliation(s)
- Francesca L. Short
- grid.1004.50000 0001 2158 5405Department of Molecular Sciences, Macquarie University, North Ryde, NSW Australia ,grid.1002.30000 0004 1936 7857Department of Microbiology, Biomedicine Discovery Institute, Monash University, Clayton, VIC Australia
| | - Qi Liu
- grid.1004.50000 0001 2158 5405Department of Molecular Sciences, Macquarie University, North Ryde, NSW Australia
| | - Bhumika Shah
- grid.1004.50000 0001 2158 5405Department of Molecular Sciences, Macquarie University, North Ryde, NSW Australia
| | - Heather E. Clift
- grid.1004.50000 0001 2158 5405Department of Molecular Sciences, Macquarie University, North Ryde, NSW Australia ,grid.280427.b0000 0004 0434 015XPresent Address: Versiti Blood Research Institute, Milwaukee, WI USA
| | - Varsha Naidu
- grid.1004.50000 0001 2158 5405Department of Molecular Sciences, Macquarie University, North Ryde, NSW Australia
| | - Liping Li
- grid.1004.50000 0001 2158 5405Department of Molecular Sciences, Macquarie University, North Ryde, NSW Australia
| | - Farzana T. Prity
- grid.1004.50000 0001 2158 5405Department of Molecular Sciences, Macquarie University, North Ryde, NSW Australia
| | - Bridget C. Mabbutt
- grid.1004.50000 0001 2158 5405Department of Molecular Sciences, Macquarie University, North Ryde, NSW Australia
| | - Karl A. Hassan
- grid.266842.c0000 0000 8831 109XSchool of Environmental and Life Sciences, University of Newcastle, Callaghan, NSW Australia
| | - Ian T. Paulsen
- grid.1004.50000 0001 2158 5405Department of Molecular Sciences, Macquarie University, North Ryde, NSW Australia
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10
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Corral J, Pérez-Varela M, Sánchez-Osuna M, Cortés P, Barbé J, Aranda J. Importance of twitching and surface-associated motility in the virulence of Acinetobacter baumannii. Virulence 2021; 12:2201-2213. [PMID: 34515614 PMCID: PMC8451467 DOI: 10.1080/21505594.2021.1950268] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
Acinetobacter baumannii is a pathogen of increasing clinical importance worldwide, especially given its ability to readily acquire resistance determinants. Motile strains of this bacterium can move by either or both of two types of motility: (i) twitching, driven by type IV pili, and (ii) surface-associated motility, an appendage-independent form of movement. A. baumannii strain MAR002 possesses both twitching and surface-associated motility. In this study, we isolated spontaneous rifampin-resistant mutants of strain MAR002 in which point mutations in the rpoB gene were identified that resulted in an altered motility pattern. Transcriptomic analysis of mutants lacking twitching, surface-associated motility, or both led to the identification of deregulated genes within each motility phenotype, based on their level of expression and their biological function. Investigations of the corresponding knockout mutants revealed several genes involved in the motility of A. baumannii strain MAR002, including two involved in twitching (encoding a minor pilin subunit and an RND [resistance nodulation division] component), one in surface-associated motility (encoding an amino acid permease), and eight in both (encoding RND and ABC components, the energy transducer TonB, the porin OprD, the T6SS component TagF, an IclR transcriptional regulator, a PQQ-dependent sugar dehydrogenase, and a putative pectate lyase). Virulence assays showed the reduced pathogenicity of mutants with impairments in both types of motility or in surface-associated motility alone. By contrast, the virulence of twitching-affected mutants was not affected. These results shed light on the key role of surface-associated motility and the limited role of twitching in the pathogenicity of A. baumannii.
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Affiliation(s)
- Jordi Corral
- Departament De Genètica I Microbiologia, Facultat De Biociènces, Universitat Autònoma De Barcelona, Barcelona, Spain
| | - María Pérez-Varela
- Departament De Genètica I Microbiologia, Facultat De Biociènces, Universitat Autònoma De Barcelona, Barcelona, Spain
| | - Miquel Sánchez-Osuna
- Departament De Genètica I Microbiologia, Facultat De Biociènces, Universitat Autònoma De Barcelona, Barcelona, Spain
| | - Pilar Cortés
- Departament De Genètica I Microbiologia, Facultat De Biociènces, Universitat Autònoma De Barcelona, Barcelona, Spain
| | - Jordi Barbé
- Departament De Genètica I Microbiologia, Facultat De Biociènces, Universitat Autònoma De Barcelona, Barcelona, Spain
| | - Jesús Aranda
- Departament De Genètica I Microbiologia, Facultat De Biociènces, Universitat Autònoma De Barcelona, Barcelona, Spain
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11
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Lin GH, Hsieh MC, Shu HY. Role of Iron-Containing Alcohol Dehydrogenases in Acinetobacter baumannii ATCC 19606 Stress Resistance and Virulence. Int J Mol Sci 2021; 22:ijms22189921. [PMID: 34576087 PMCID: PMC8465190 DOI: 10.3390/ijms22189921] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2021] [Revised: 09/11/2021] [Accepted: 09/13/2021] [Indexed: 11/21/2022] Open
Abstract
Most bacteria possess alcohol dehydrogenase (ADH) genes (Adh genes) to mitigate alcohol toxicity, but these genes have functions beyond alcohol degradation. Previous research has shown that ADH can modulate quorum sensing in Acinetobacter baumannii, a rising opportunistic pathogen. However, the number and nature of Adh genes in A. baumannii have not yet been fully characterized. We identified seven alcohol dehydrogenases (NAD+-ADHs) from A. baumannii ATCC 19606, and examined the roles of three iron-containing ADHs, ADH3, ADH4, and ADH6. Marker-less mutation was used to generate Adh3, Adh4, and Adh6 single, double, and triple mutants. Disrupted Adh4 mutants failed to grow in ethanol-, 1-butanol-, or 1-propanol-containing mediums, and recombinant ADH4 exhibited strongest activity against ethanol. Stress resistance assays with inorganic and organic hydroperoxides showed that Adh3 and Adh6 were key to oxidative stress resistance. Virulence assays performed on the Galleria mellonella model organism revealed that Adh4 mutants had comparable virulence to wild-type, while Adh3 and Adh6 mutants had reduced virulence. The results suggest that ADH4 is primarily involved in alcohol metabolism, while ADH3 and ADH6 are key to stress resistance and virulence. Further investigation into the roles of other ADHs in A. baumannii is warranted.
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Affiliation(s)
- Guang-Huey Lin
- Master Program of Microbiology and Immunology, School of Medicine, Tzu Chi University, Hualien 97004, Taiwan; (G.-H.L.); (M.-C.H.)
- Department of Microbiology, School of Medicine, Tzu Chi University, Hualien 97004, Taiwan
- International College, Tzu Chi University, Hualien 97004, Taiwan
| | - Ming-Chuan Hsieh
- Master Program of Microbiology and Immunology, School of Medicine, Tzu Chi University, Hualien 97004, Taiwan; (G.-H.L.); (M.-C.H.)
| | - Hung-Yu Shu
- Department of Bioscience Technology, Chang Jung Christian University, Tainan 71101, Taiwan
- Correspondence: ; Tel.: +886-6-278-5123 (ext. 3211); Fax: +886-6-278-5010
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D'Souza R, Nguyen LP, Pinto NA, Lee H, Vu TN, Kim H, Cho HS, Yong D. Role of AmpG in the resistance to β-lactam agents, including cephalosporins and carbapenems: candidate for a novel antimicrobial target. Ann Clin Microbiol Antimicrob 2021; 20:45. [PMID: 34134705 PMCID: PMC8207665 DOI: 10.1186/s12941-021-00446-7] [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: 05/27/2020] [Accepted: 05/24/2021] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND A complex cascade of genes, enzymes, and transcription factors regulates AmpC β-lactamase overexpression. We investigated the network of AmpC β-lactamase overexpression in Klebsiella aerogenes and identified the role of AmpG in resistance to β-lactam agents, including cephalosporins and carbapenems. METHODS A transposon mutant library was created for carbapenem-resistant K. aerogenes YMC2008-M09-943034 (KE-Y1) to screen for candidates with increased susceptibility to carbapenems, which identified the susceptible mutant derivatives KE-Y3 and KE-Y6. All the strains were subjected to highly contiguous de novo assemblies using PacBio sequencing to investigate the loss of resistance due to transposon insertion. Complementation and knock-out experiments using lambda Red-mediated homologous recombinase and CRISPR-Cas9 were performed to confirm the role of gene of interest. RESULTS In-depth analysis of KE-Y3 and KE-Y6 revealed the insertion of a transposon at six positions in each strain, at which truncation of the AmpG permease gene was common in both. The disruption of the AmpG permease leads to carbapenem susceptibility, which was further confirmed by complementation. We generated an AmpG permease gene knockout using lambda Red-mediated recombineering in K. aerogenes KE-Y1 and a CRISPR-Cas9-mediated gene knockout in multidrug-resistant Klebsiella pneumoniae-YMC/2013/D to confer carbapenem susceptibility. CONCLUSIONS These findings suggest that inhibition of the AmpG is a potential strategy to increase the efficacy of β-lactam agents against Klebsiella aerogenes.
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Affiliation(s)
- Roshan D'Souza
- Department of Laboratory Medicine and Research Institute of Bacterial Resistance, Yonsei University College of Medicine, 50-1 Yonsei-ro, Seodaemun-gu, Seoul, 03722, Korea.,J. Craig Venter Institute, Rockville, MD, USA
| | - Le Phuong Nguyen
- Department of Laboratory Medicine and Research Institute of Bacterial Resistance, Yonsei University College of Medicine, 50-1 Yonsei-ro, Seodaemun-gu, Seoul, 03722, Korea.,Brain Korea 21+ Project for Medical Science, Yonsei University, Seoul, Korea
| | - Naina A Pinto
- Brain Korea 21+ Project for Medical Science, Yonsei University, Seoul, Korea
| | - Hyunsook Lee
- Department of Laboratory Medicine and Research Institute of Bacterial Resistance, Yonsei University College of Medicine, 50-1 Yonsei-ro, Seodaemun-gu, Seoul, 03722, Korea.,Brain Korea 21+ Project for Medical Science, Yonsei University, Seoul, Korea
| | - Thao Nguyen Vu
- Department of Laboratory Medicine and Research Institute of Bacterial Resistance, Yonsei University College of Medicine, 50-1 Yonsei-ro, Seodaemun-gu, Seoul, 03722, Korea.,Brain Korea 21+ Project for Medical Science, Yonsei University, Seoul, Korea
| | - Hoyoung Kim
- Department of Systems Biology, Yonsei University, Seoul, Korea
| | - Hyun Soo Cho
- Department of Systems Biology, Yonsei University, Seoul, Korea
| | - Dongeun Yong
- Department of Laboratory Medicine and Research Institute of Bacterial Resistance, Yonsei University College of Medicine, 50-1 Yonsei-ro, Seodaemun-gu, Seoul, 03722, Korea.
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13
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Gil-Marqués ML, Labrador Herrera G, Miró Canturri A, Pachón J, Smani Y, Pachón-Ibáñez ME. Role of PstS in the Pathogenesis of Acinetobacter baumannii Under Microaerobiosis and Normoxia. J Infect Dis 2021; 222:1204-1212. [PMID: 32324853 DOI: 10.1093/infdis/jiaa201] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2019] [Accepted: 04/20/2020] [Indexed: 01/15/2023] Open
Abstract
Acinetobacter baumannii is a successful pathogen responsible for infections with high mortality rate. During the course of infection it can be found in microaerobic environments, which influences virulence factor expression. From a previous transcriptomic analysis of A. baumannii ATCC 17978 under microaerobiosis, we know the gene pstS is overexpressed under microaerobiosis. Here, we studied its role in A. baumannii virulence. pstS loss significantly decreased bacterial adherence and invasion into A549 cells and increased A549 cell viability. pstS loss also reduced motility and biofilm-forming ability of A. baumannii. In a peritoneal sepsis murine model, the minimum lethal dose required by A. baumannii ATCC 17978 ΔpstS was lower compared to the wild type (4.3 vs 3.2 log colony forming units/mL, respectively), and the bacterial burden in tissues and fluids was lower. Thus, the loss of the phosphate sensor PstS produced a decrease in A. baumannii pathogenesis, supporting its role as a virulence factor.
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Affiliation(s)
- María Luisa Gil-Marqués
- Clinical Unit of Infectious Diseases, Microbiology, and Preventive Medicine, Institute of Biomedicine of Seville, University Hospital Virgen del Rocío, Consejo Superior de Investigaciones Científicas, University of Seville, Seville, Spain
| | - Gema Labrador Herrera
- Clinical Unit of Infectious Diseases, Microbiology, and Preventive Medicine, Institute of Biomedicine of Seville, University Hospital Virgen del Rocío, Consejo Superior de Investigaciones Científicas, University of Seville, Seville, Spain
| | - Andrea Miró Canturri
- Clinical Unit of Infectious Diseases, Microbiology, and Preventive Medicine, Institute of Biomedicine of Seville, University Hospital Virgen del Rocío, Consejo Superior de Investigaciones Científicas, University of Seville, Seville, Spain
| | - Jerónimo Pachón
- Clinical Unit of Infectious Diseases, Microbiology, and Preventive Medicine, Institute of Biomedicine of Seville, University Hospital Virgen del Rocío, Consejo Superior de Investigaciones Científicas, University of Seville, Seville, Spain
- Department of Medicine, University of Seville, Seville, Spain
| | - Younes Smani
- Clinical Unit of Infectious Diseases, Microbiology, and Preventive Medicine, Institute of Biomedicine of Seville, University Hospital Virgen del Rocío, Consejo Superior de Investigaciones Científicas, University of Seville, Seville, Spain
| | - María Eugenia Pachón-Ibáñez
- Clinical Unit of Infectious Diseases, Microbiology, and Preventive Medicine, Institute of Biomedicine of Seville, University Hospital Virgen del Rocío, Consejo Superior de Investigaciones Científicas, University of Seville, Seville, Spain
- Department of Medicine, University of Seville, Seville, Spain
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14
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Chen CL, Dudek A, Liang YH, Janapatla RP, Lee HY, Hsu L, Kuo HY, Chiu CH. d-mannose-sensitive pilus of Acinetobacter baumannii is linked to biofilm formation and adherence onto respiratory tract epithelial cells. JOURNAL OF MICROBIOLOGY, IMMUNOLOGY, AND INFECTION = WEI MIAN YU GAN RAN ZA ZHI 2021; 55:69-79. [PMID: 33610507 DOI: 10.1016/j.jmii.2021.01.008] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/12/2020] [Revised: 01/10/2021] [Accepted: 01/26/2021] [Indexed: 11/25/2022]
Abstract
BACKGROUND/PURPOSE Acinetobacter baumannii is an important nosocomial pathogen. To better understand the role of CsuA/BABCDE pilus of A. baumannii in virulence, bacterial biofilm formation, adherence and carbohydrate-mediated inhibition were conducted. METHODS CsuA/BABCDE pilus-producing (abbreviated Csu pilus) operon of A. baumannii ATCC17978 was cloned for analysis of biofilm formation on an abiotic plastic plate, bacterial adherence to respiratory epithelial human A549 cells and carbohydrate-mediated inhibition. The carbohydrates used for inhibition of biofilm formation and adherence to A549 cells included monosaccharides, pyranosides, and mannose-polymers. RESULTS The Csu pilus of A. baumannii ATCC17978 was cloned and expressed into a non-pilus-producing Escherichia coli JM109, and was knocked out as well. The recombinant Csu (rCsu) pilus on E. coli JM109/rCsu pilus-producing clone observed by both electro-microscopy and atomic force microscopy showed abundant, while Csu-knockout A. baumannii ATCC17978 mutant appeared less or no pilus production. The E. coli JM109/rCsu pilus-producing clone significantly increased biofilm formation and adherence to A549 cells; however, the Csu-knockout mutant dramatically lost biofilm-making ability but, in contrast, increased adherence. Moreover, both of biofilm formation and adherence could be significantly inhibited by d-mannose and methyl-α-d-mannopyranoside in Csu pilus-producing E. coli JM109, whereas in A. baumannii ATCC17978, high concentration of carbohydrates was required for the inhibition, suggesting that Csu pilus is sensitive to d-mannose. CONCLUSION This is the first study confirming that Csu pilus of A. baumannii belongs to mannose-sensitive type 1 pilus family and contributes to biofilm formation and bacterial adherence to human epithelial cells.
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Affiliation(s)
- Chyi-Liang Chen
- Molecular Infectious Disease Research Center, Chang Gung Memorial Hospital, Taoyuan, Taiwan
| | - Anna Dudek
- Molecular Infectious Disease Research Center, Chang Gung Memorial Hospital, Taoyuan, Taiwan
| | - Yi-Hua Liang
- Molecular Infectious Disease Research Center, Chang Gung Memorial Hospital, Taoyuan, Taiwan
| | | | - Hao-Yuan Lee
- Molecular Infectious Disease Research Center, Chang Gung Memorial Hospital, Taoyuan, Taiwan; Department of Nursing, Jen-Teh Junior College of Medicine, Nursing and Management, Miaoli, Taiwan; Department of Pediatrics, Wei Gong Memorial Hospital, Miaoli, Taiwan; School of Medicine, College of Medicine, Fu Jen Catholic University, New Taipei, Taiwan
| | - Long Hsu
- Department of Electrophysics, National Chiao Tung University, Hsinchu, Taiwan
| | - Han-Yueh Kuo
- Division of Infectious Disease, Department of Internal Medicine, National Taiwan University Hospital, Hsinchu Branch, Hsinchu, Taiwan
| | - Cheng-Hsun Chiu
- Molecular Infectious Disease Research Center, Chang Gung Memorial Hospital, Taoyuan, Taiwan; Department of Pediatrics, Chang Gung Memorial Hospital, Chang Gung University College of Medicine, Taoyuan, Taiwan.
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15
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Corral J, Pérez-Varela M, Barbé J, Aranda J. Direct interaction between RecA and a CheW-like protein is required for surface-associated motility, chemotaxis and the full virulence of Acinetobacter baumannii strain ATCC 17978. Virulence 2021; 11:315-326. [PMID: 32255384 PMCID: PMC7161683 DOI: 10.1080/21505594.2020.1748923] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
Acinetobacter baumannii is a nosocomial pathogen that causes multi-drug resistant infections mainly in immunocompromised patients. Although this gram-negative species lacks flagella, it is able to move over wet surfaces through a not well characterized type of movement known as surface-associated motility. In this study we demonstrate through the inactivation of the A1S_2813 gene (coding a CheW-like protein) and recA (coding a DNA damage repair and recombination protein) that both genes are involved in the surface-associated motility and chemotaxis of A. baumannii ATCC 17978 strain. In addition, we also point out that the lack of either RecA or CheW-like proteins reduces its virulence in the Caenorhabditis elegans and the Galleria mellonella animal models. Furthermore, we show through co-immunoprecipitation assays that the CheW-like protein and RecA interact and that this interaction is abolished by the introduction of the mutation S97A in one of the domains of CheW-like protein that is structurally conserved in Salmonella enterica and necessary for the RecA-CheW interaction in this bacterial species. Finally, we show that the replacement of the wild-type CheW-like protein by that presenting the S97A mutation impairs surface-associated motility, chemotaxis and virulence of A. baumannii strain ATCC 17978.
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Affiliation(s)
- Jordi Corral
- Departament de Genètica i Microbiologia, Facultat de Biociènces, Universitat Autònoma de Barcelona, Bellaterra, Spain
| | - María Pérez-Varela
- Departament de Genètica i Microbiologia, Facultat de Biociènces, Universitat Autònoma de Barcelona, Bellaterra, Spain
| | - Jordi Barbé
- Departament de Genètica i Microbiologia, Facultat de Biociènces, Universitat Autònoma de Barcelona, Bellaterra, Spain
| | - Jesús Aranda
- Departament de Genètica i Microbiologia, Facultat de Biociènces, Universitat Autònoma de Barcelona, Bellaterra, Spain
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The H-NS Regulator Plays a Role in the Stress Induced by Carbapenemase Expression in Acinetobacter baumannii. mSphere 2020; 5:5/4/e00793-20. [PMID: 32848010 PMCID: PMC7449629 DOI: 10.1128/msphere.00793-20] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Carbapenem-resistant A. baumannii (CRAB) is recognized as one of the most threatening Gram-negative bacilli. H-NS is known to play a role in controlling the transcription of a variety of different genes, including those associated with the stress response, persistence, and virulence. In the present work, we uncovered a link between the role of H-NS in the A. baumannii stress response and its relationship with the envelope stress response and resistance to DNA-damaging agents. Overall, we posit a new role of H-NS, showing that H-NS serves to endure envelope stress and could also be a mechanism that alleviates the stress induced by MBL expression in A. baumannii. This could be an evolutionary advantage to further resist the action of carbapenems. Disruption of the histone-like nucleoid structuring protein (H-NS) was shown to affect the ability of Gram-negative bacteria to regulate genes associated with virulence, persistence, stress response, quorum sensing, biosynthesis pathways, and cell adhesion. Here, we used the expression of metallo-β-lactamases (MBLs), known to elicit envelope stress by the accumulation of toxic precursors in the periplasm, to interrogate the role of H-NS in Acinetobacter baumannii, together with other stressors. Using a multidrug-resistant A. baumannii strain, we observed that H-NS plays a role in alleviating the stress triggered by MBL toxic precursors and counteracts the effect of DNA-damaging agents, supporting its role in stress response. IMPORTANCE Carbapenem-resistant A. baumannii (CRAB) is recognized as one of the most threatening Gram-negative bacilli. H-NS is known to play a role in controlling the transcription of a variety of different genes, including those associated with the stress response, persistence, and virulence. In the present work, we uncovered a link between the role of H-NS in the A. baumannii stress response and its relationship with the envelope stress response and resistance to DNA-damaging agents. Overall, we posit a new role of H-NS, showing that H-NS serves to endure envelope stress and could also be a mechanism that alleviates the stress induced by MBL expression in A. baumannii. This could be an evolutionary advantage to further resist the action of carbapenems.
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17
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Rodríguez D, Maneiro M, Vázquez-Ucha JC, Beceiro A, González-Bello C. 6-Arylmethylidene Penicillin-Based Sulfone Inhibitors for Repurposing Antibiotic Efficiency in Priority Pathogens. J Med Chem 2020; 63:3737-3755. [PMID: 32196336 DOI: 10.1021/acs.jmedchem.0c00127] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The ability of 6-(aryl)methylidene penicillin-based sulfones 1-7 to repurpose β-lactam antibiotics activity with bacterial species that carry carbapenem-hydrolyzing class D β-lactamases (OXA-23, OXA-24/40 and OXA-48), as well as with class A (TEM-1, CTX-M-2) and class C (CMY-2, DHA-1) enzymes, is reported. The combinations imipenem/3 and imipenem/4 restored almost completely the antibiotic efficacy in OXA-23 and OXA-24/40 carbapenemase-producing A. baumannii strains (1 μg mL-1) and also provided good results for OXA-48 carbapenemase-producing K. pneumoniae strains (4 μg mL-1). Compounds 2-6 in combinations with ceftazidime and ampicillin were also efficient in restoring antibiotic efficacy in E. coli strains carrying class C (CMY-2 and DHA-1) and class A (TEM-1 and CTX-M-2) β-lactamase enzymes, respectively. Kinetic and inhibition studies with the OXA-24/40 enzyme, protein mass spectrometry analysis and docking studies allowed us to gain an insight into the inhibition mechanism and the experimentally observed differences between the ligands.
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Affiliation(s)
- Diana Rodríguez
- Centro Singular de Investigación en Química Biolóxica e Materiais Moleculares (CiQUS), Departamento de Química Orgánica, Universidade de Santiago de Compostela, Jenaro de la Fuente s/n, 15782 Santiago de Compostela, Spain
| | - María Maneiro
- Centro Singular de Investigación en Química Biolóxica e Materiais Moleculares (CiQUS), Departamento de Química Orgánica, Universidade de Santiago de Compostela, Jenaro de la Fuente s/n, 15782 Santiago de Compostela, Spain
| | - Juan C Vázquez-Ucha
- Servicio de Microbiología do Complexo Hospitalario Universitario da Coruña (CHUAC), Instituto de Investigación Biomédica da Coruña (INIBIC), Xubias de Arriba, 84, 15006 A Coruña, Spain
| | - Alejandro Beceiro
- Servicio de Microbiología do Complexo Hospitalario Universitario da Coruña (CHUAC), Instituto de Investigación Biomédica da Coruña (INIBIC), Xubias de Arriba, 84, 15006 A Coruña, Spain
| | - Concepción González-Bello
- Centro Singular de Investigación en Química Biolóxica e Materiais Moleculares (CiQUS), Departamento de Química Orgánica, Universidade de Santiago de Compostela, Jenaro de la Fuente s/n, 15782 Santiago de Compostela, Spain
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Cafiso V, Stracquadanio S, Lo Verde F, Dovere V, Zega A, Pigola G, Aranda J, Stefani S. COL R Acinetobacter baumannii sRNA Signatures: Computational Comparative Identification and Biological Targets. Front Microbiol 2020; 10:3075. [PMID: 32010115 PMCID: PMC6978653 DOI: 10.3389/fmicb.2019.03075] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2019] [Accepted: 12/19/2019] [Indexed: 11/25/2022] Open
Abstract
Multidrug-Resistant (MDR) and Extensively Drug Resistant (XDR) Acinetobacter baumannii (Ab) represent a serious cause of healthcare-associated infections worldwide. Currently, the available treatment options are very restricted and colistin-based therapies are last-line treatments of these infections, even though colistin resistant (COLR) Ab have rarely been isolated yet. In bacteria, small non-coding RNAs (sRNAs) have been implicated in regulatory pathways of different biological functions, however, no knowledge exists about the sRNA role on the biological adaptation in COLRAb. Our study investigated two Italian XDR isogenic colistin-susceptible/resistant (COLS/R) Ab strain-pairs to discover new sRNA signatures. Comparative sRNA transcriptome (sRNAome) analyses were carried out by Illumina RNA-seq using both a Tru-Seq and a Short Insert library, whilst Ab ATCC 17978 and ACICU Reference Genome assembly, mapping, annotation and statistically significant differential expression (q-value ≤ 0.01) of the raw reads were performed by the Rockhopper tool. A computational filtering, sorting only similarly statistically significant differentially expressed (DE) sRNAs mapping on the same gene in both COLRAb isolates was conducted. COLR vs. COLS sRNAome, analyzed integrating the DE sRNAs obtained from the two different libraries, revealed some statistically significant DE sRNAs in COLRAb. In detail, we found: (i) two different under-expressed cis-acting sRNAs (AbsRNA1 and AbsRNA2) mapping in antisense orientation the 16S rRNA gene A1S_r01, (ii) one under-expressed cis-acting sRNA (AbsRNA3) targeting the A1S_2505 gene (hypothetical protein), (iii) one under-expressed microRNA-size small RNA fragment (AbsRNA4) and its pre-microAbsRNA4 targeting the A1S_0501 gene (hypothetical protein), (iv) as well as an over-expressed microRNA-size small RNA fragment (AbsRNA5) and its pre-microAbsRNA5 targeting the A1S_3097 gene (signal peptide). Custom TaqMan® probe-based real-time qPCRs validated the expression pattern of the selected sRNA candidates shown by RNA-seq. Furthermore, analysis on sRNA ΔA1S_r01, ΔA1S_2505 as well as the over-expressed A1S_3097 mutants revealed no effects on colistin resistance. Our study, for the first time, found the sRNAome signatures of clinical COLRAb with a computational prediction of their targets related to protein synthesis, host-microbe interaction and other different biological functions, including biofilm production, cell-cycle control, virulence, and antibiotic-resistance.
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Affiliation(s)
- Viviana Cafiso
- Department of Biomedical and Biotechnological Sciences, University of Catania, Catania, Italy
| | - Stefano Stracquadanio
- Department of Biomedical and Biotechnological Sciences, University of Catania, Catania, Italy
| | - Flavia Lo Verde
- Department of Biomedical and Biotechnological Sciences, University of Catania, Catania, Italy
| | - Veronica Dovere
- Department of Translational Research and New Technology in Medicine and Surgery, Azienda Ospedaliero Universitaria Pisana, University of Pisa, Pisa, Italy
| | - Alessandra Zega
- Department of Biomedical and Biotechnological Sciences, University of Catania, Catania, Italy
| | - Giuseppe Pigola
- Department of Clinical and Experimental Medicine, University of Catania, Catania, Italy
| | - Jesús Aranda
- Departament de Genètica i Microbiologia, Facultat de Biociènces, Universitat Autònoma de Barcelona, Barcelona, Spain
| | - Stefania Stefani
- Department of Biomedical and Biotechnological Sciences, University of Catania, Catania, Italy
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Robust Suppression of Lipopolysaccharide Deficiency in Acinetobacter baumannii by Growth in Minimal Medium. J Bacteriol 2019; 201:JB.00420-19. [PMID: 31451545 DOI: 10.1128/jb.00420-19] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2019] [Accepted: 08/19/2019] [Indexed: 12/12/2022] Open
Abstract
Lipopolysaccharide (LPS) is normally considered to be essential for viability in Gram-negative bacteria but can be removed in Acinetobacter baumannii Mutant cells lacking this component of the outer membrane show growth and morphological defects. Here, we report that growth rates equivalent to the wild type can be achieved simply by propagation in minimal medium. The loss of LPS requires that cells rely on phospholipids for both leaflets of the outer membrane. We show that growth rate in the absence of LPS is not limited by nutrient availability but by the rate of outer membrane biogenesis. We hypothesize that because cells grow more slowly, outer membrane synthesis ceases to be rate limiting in minimal medium.IMPORTANCE Gram-negative bacteria are defined by their asymmetric outer membrane that consists of phospholipids on the inner leaflet and lipopolysaccharide (LPS) in the outer leaflet. LPS is essential in all but a few Gram-negative species; the reason for this differential essentiality is not well understood. One species that can survive without LPS, Acinetobacter baumannii, shows characteristic growth and morphology phenotypes. We show that these phenotypes can be suppressed under conditions of slow growth and describe how LPS loss is connected to the growth defects. In addition to better defining the challenges A. baumannii cells face in the absence of LPS, we provide a new hypothesis that may explain the species-dependent conditional essentiality.
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Gil-Marqués ML, Moreno-Martínez P, Costas C, Pachón J, Blázquez J, McConnell MJ. Peptidoglycan recycling contributes to intrinsic resistance to fosfomycin in Acinetobacter baumannii. J Antimicrob Chemother 2019; 73:2960-2968. [PMID: 30124902 DOI: 10.1093/jac/dky289] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2018] [Accepted: 06/25/2018] [Indexed: 12/15/2022] Open
Abstract
Background Acinetobacter baumannii is intrinsically resistant to fosfomycin; however, the mechanisms underlying this resistance are poorly understood. Objectives To identify and characterize genes that contribute to intrinsic fosfomycin resistance in A. baumannii. Methods More than 9000 individual transposon mutants of the A. baumannii ATCC 17978 strain (fosfomycin MIC ≥1024 mg/L) were screened to identify mutations conferring increased susceptibility to fosfomycin. In-frame deletion mutants were constructed for the identified genes and their susceptibility to fosfomycin was characterized by MIC determination and growth in the presence of fosfomycin. The effects of these mutations on membrane permeability and peptidoglycan integrity were characterized. Susceptibilities to 21 antibiotics were determined for the mutant strains. Results Screening of the transposon library identified mutants in the ampD and anmK genes, both encoding enzymes of the peptidoglycan recycling pathway, that demonstrated increased susceptibility to fosfomycin. MIC values for in-frame deletion mutants were ≥42-fold (ampD) and ≥8-fold (anmK) lower than those for the parental strain, and growth of the mutant strains in the presence of 32 mg/L fosfomycin was significantly reduced. Neither mutation resulted in increased cell permeability; however, the ampD mutant demonstrated decreased peptidoglycan integrity. Susceptibility to 21 antibiotics was minimally affected by mutations in ampD and anmK. Conclusions This study demonstrates that AmpD and AnmK of the peptidoglycan recycling pathway contribute to intrinsic fosfomycin resistance in A. baumannii, indicating that inhibitors of these enzymes could be used in combination with fosfomycin as a novel treatment approach for MDR A. baumannii.
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Affiliation(s)
- María Luisa Gil-Marqués
- Clinical Unit of Infectious Diseases, Clinical Microbiology and Preventive Medicine, Institute of Biomedicine of Seville (IBiS), University Hospital Virgen del Rocío/CSIC/University of Seville, Seville, Spain
| | - Patricia Moreno-Martínez
- Clinical Unit of Infectious Diseases, Clinical Microbiology and Preventive Medicine, Institute of Biomedicine of Seville (IBiS), University Hospital Virgen del Rocío/CSIC/University of Seville, Seville, Spain
| | - Coloma Costas
- Clinical Unit of Infectious Diseases, Clinical Microbiology and Preventive Medicine, Institute of Biomedicine of Seville (IBiS), University Hospital Virgen del Rocío/CSIC/University of Seville, Seville, Spain
| | - Jerónimo Pachón
- Clinical Unit of Infectious Diseases, Clinical Microbiology and Preventive Medicine, Institute of Biomedicine of Seville (IBiS), University Hospital Virgen del Rocío/CSIC/University of Seville, Seville, Spain.,Department of Medicine, University of Seville, Seville, Spain
| | - Jesús Blázquez
- Centro Nacional de Biotecnología (CNB), Consejo Superior de Investigaciones Científicas (CSIC), Madrid, Spain
| | - Michael J McConnell
- Clinical Unit of Infectious Diseases, Clinical Microbiology and Preventive Medicine, Institute of Biomedicine of Seville (IBiS), University Hospital Virgen del Rocío/CSIC/University of Seville, Seville, Spain
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21
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Intercellular Transfer of Chromosomal Antimicrobial Resistance Genes between Acinetobacter baumannii Strains Mediated by Prophages. Antimicrob Agents Chemother 2019; 63:AAC.00334-19. [PMID: 31138576 DOI: 10.1128/aac.00334-19] [Citation(s) in RCA: 31] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2019] [Accepted: 05/22/2019] [Indexed: 01/01/2023] Open
Abstract
The spread of antimicrobial resistance genes (ARGs) among Gram-negative pathogens, including Acinetobacter baumannii, is primarily mediated by transferable plasmids; however, ARGs are frequently integrated into its chromosome. How ARG gets horizontally incorporated into the chromosome of A. baumannii, and whether it functions as a cause for further spread of ARG, remains unknown. Here, we demonstrated intercellular prophage-mediated transfer of chromosomal ARGs without direct cell-cell interaction in A. baumannii We prepared ARG-harboring extracellular DNA (eDNA) components from the culture supernatant of a multidrug-resistant (MDR) A. baumannii NU-60 strain and exposed an antimicrobial-susceptible (AS) A. baumannii ATCC 17978 strain to the eDNA components. The antimicrobial-resistant (AR) A. baumannii ATCC 17978 derivatives appeared to acquire various ARGs, originating from dispersed loci of the MDR A. baumannii chromosome, along with their surrounding regions, by homologous recombination, with the ARGs including armA (aminoglycoside resistance), bla TEM-1 (β-lactam resistance), tet(B) (tetracycline resistance), and gyrA-81L (nalidixic acid resistance) genes. Notably, the eDNAs conferring antimicrobial resistance were enveloped in specific capsid proteins consisting of phage particles, thereby protecting the eDNAs from detergent and DNase treatments. The phages containing ARGs were likely released into the extracellular space from MDR A. baumannii, thereby transducing ARGs into AS A. baumannii, resulting in the acquisition of AR properties by the recipient. We concluded that the generalized transduction, in which phages were capable of carrying random pieces of A. baumannii genomic DNAs, enabled efficacious intercellular transfer of chromosomal ARGs between A. baumannii strains without direct cell-cell interaction.
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Tuttobene MR, Fernández-García L, Blasco L, Cribb P, Ambroa A, Müller GL, Fernández-Cuenca F, Bleriot I, Rodríguez RE, Barbosa BGV, Lopez-Rojas R, Trastoy R, López M, Bou G, Tomás M, Mussi MA. Quorum and Light Signals Modulate Acetoin/Butanediol Catabolism in Acinetobacter spp. Front Microbiol 2019; 10:1376. [PMID: 31281296 PMCID: PMC6595428 DOI: 10.3389/fmicb.2019.01376] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2019] [Accepted: 06/03/2019] [Indexed: 12/25/2022] Open
Abstract
Acinetobacter spp. are found in all environments on Earth due to their extraordinary capacity to survive in the presence of physical and chemical stressors. In this study, we analyzed global gene expression in airborne Acinetobacter sp. strain 5-2Ac02 isolated from hospital environment in response to quorum network modulators and found that they induced the expression of genes of the acetoin/butanediol catabolism, volatile compounds shown to mediate interkingdom interactions. Interestingly, the acoN gene, annotated as a putative transcriptional regulator, was truncated in the downstream regulatory region of the induced acetoin/butanediol cluster in Acinetobacter sp. strain 5-2Ac02, and its functioning as a negative regulator of this cluster integrating quorum signals was confirmed in Acinetobacter baumannii ATCC 17978. Moreover, we show that the acetoin catabolism is also induced by light and provide insights into the light transduction mechanism by showing that the photoreceptor BlsA interacts with and antagonizes the functioning of AcoN in A. baumannii, integrating also a temperature signal. The data support a model in which BlsA interacts with and likely sequesters AcoN at this condition, relieving acetoin catabolic genes from repression, and leading to better growth under blue light. This photoregulation depends on temperature, occurring at 23°C but not at 30°C. BlsA is thus a dual regulator, modulating different transcriptional regulators in the dark but also under blue light, representing thus a novel concept. The overall data show that quorum modulators as well as light regulate the acetoin catabolic cluster, providing a better understanding of environmental as well as clinical bacteria.
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Affiliation(s)
- Marisel Romina Tuttobene
- Centro de Estudios Fotosintéticos y Bioquímicos de Rosario (CEFOBI-CONICET), Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, Rosario, Argentina
| | - Laura Fernández-García
- Microbiology Department-Biomedical Research Institute A Coruña (INIBIC), Hospital A Coruña (CHUAC), University of A Coruña (UDC), A Coruña, Spain
| | - Lucía Blasco
- Microbiology Department-Biomedical Research Institute A Coruña (INIBIC), Hospital A Coruña (CHUAC), University of A Coruña (UDC), A Coruña, Spain
| | - Pamela Cribb
- Instituto de Biología Molecular y Celular de Rosario (IBR-CONICET), Rosario, Argentina
| | - Anton Ambroa
- Microbiology Department-Biomedical Research Institute A Coruña (INIBIC), Hospital A Coruña (CHUAC), University of A Coruña (UDC), A Coruña, Spain
| | - Gabriela Leticia Müller
- Centro de Estudios Fotosintéticos y Bioquímicos de Rosario (CEFOBI-CONICET), Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, Rosario, Argentina
| | - Felipe Fernández-Cuenca
- Clinical Unit for Infectious Diseases, Microbiology and Preventive Medicine, Hospital Universitario Virgen Macarena, Seville, Spain.,Department of Microbiology and Medicine, University of Seville, Seville, Spain.,Biomedicine Institute of Seville (IBIS), Seville, Spain
| | - Inés Bleriot
- Centro de Estudios Fotosintéticos y Bioquímicos de Rosario (CEFOBI-CONICET), Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, Rosario, Argentina
| | | | - Beatriz G V Barbosa
- Microbial Resistance Laboratory, Biological Sciences Institute, University of Pernambuco (UPE), Recife, Brazil
| | - Rafael Lopez-Rojas
- Clinical Unit for Infectious Diseases, Microbiology and Preventive Medicine, Hospital Universitario Virgen Macarena, Seville, Spain.,Department of Microbiology and Medicine, University of Seville, Seville, Spain.,Biomedicine Institute of Seville (IBIS), Seville, Spain
| | - Rocío Trastoy
- Microbiology Department-Biomedical Research Institute A Coruña (INIBIC), Hospital A Coruña (CHUAC), University of A Coruña (UDC), A Coruña, Spain
| | - María López
- Microbiology Department-Biomedical Research Institute A Coruña (INIBIC), Hospital A Coruña (CHUAC), University of A Coruña (UDC), A Coruña, Spain
| | - Germán Bou
- Centro de Estudios Fotosintéticos y Bioquímicos de Rosario (CEFOBI-CONICET), Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, Rosario, Argentina
| | - María Tomás
- Microbiology Department-Biomedical Research Institute A Coruña (INIBIC), Hospital A Coruña (CHUAC), University of A Coruña (UDC), A Coruña, Spain
| | - María A Mussi
- Centro de Estudios Fotosintéticos y Bioquímicos de Rosario (CEFOBI-CONICET), Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, Rosario, Argentina
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23
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Roles of Efflux Pumps from Different Superfamilies in the Surface-Associated Motility and Virulence of Acinetobacter baumannii ATCC 17978. Antimicrob Agents Chemother 2019; 63:AAC.02190-18. [PMID: 30642939 DOI: 10.1128/aac.02190-18] [Citation(s) in RCA: 33] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2018] [Accepted: 01/07/2019] [Indexed: 02/06/2023] Open
Abstract
Although the relationship between Acinetobacter baumannii efflux pumps and antimicrobial resistance is well documented, less is known about the involvement of these proteins in the pathogenicity of this nosocomial pathogen. In previous work, we identified the AbaQ major facilitator superfamily (MFS) efflux pump and demonstrated its participation in the motility and virulence of A. baumannii In the present study, we examined the role in these processes of A. baumannii transporters belonging to different superfamilies of efflux pumps. Genes encoding known or putative permeases belonging to efflux pump superfamilies other than the MFS were selected, and the corresponding knockouts were constructed. The antimicrobial susceptibilities of these mutants were consistent with previously reported data. In mutants of A. baumannii strain ATCC 17978 carrying inactivated genes encoding the efflux pumps A1S_2736 (resistance nodulation division [RND]), A1S_3371 (multidrug and toxic compound extrusion [MATE]), and A1S_0710 (small multidrug resistance [SMR]), as well as the newly described ATP-binding cassette (ABC) permeases A1S_1242 and A1S_2622, both surface-associated motility and virulence were reduced compared to the parental strain. However, inactivation of the genes encoding the known ABC permeases A1S_0536 and A1S_1535, the newly identified putative ABC permeases A1S_0027 and A1S_1057, or the proteobacterial antimicrobial compound efflux (PACE) transporters A1S_1503 and A1S_2063 had no effects on bacterial motility or virulence. Our results demonstrate the involvement of antimicrobial transporters belonging at least to five of the six known efflux pump superfamilies in both surface-associated motility and virulence in A. baumannii ATCC 17978.
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24
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Askelson TE, McMullin AB, Duong T. Targeted gene inactivation in Lactobacillus gallinarum ATCC 33199 using chromosomal integration. Poult Sci 2019; 98:398-403. [PMID: 30124967 DOI: 10.3382/ps/pey363] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2018] [Accepted: 08/02/2018] [Indexed: 11/20/2022] Open
Abstract
Although Lactobacillus species have been administered widely as probiotics in poultry production, the mechanisms responsible for their functionality are not well understood. The genetic tools available for use in lactobacilli are advanced but have not been applied widely to investigate their probiotic functionality in poultry. The genome sequence of Lactobacillus gallinarum ATCC 33199, originally isolated from the chicken crop, has recently been made available suggesting this organism as a potentially important model organism for probiotic research in poultry. In this study, we demonstrated the functionality of the pORI28 system for construction of isogenic knockout mutants in L. gallinarum ATCC 33199 using insertional inactivation of lacL as proof-of-principle. The establishment of an effective chromosomal integration system for use in L. gallinarum ATCC 33199 will provide a platform for functional genomic analyses to investigate the functionality of this model organism in the gastrointestinal tract of poultry.
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Affiliation(s)
- T E Askelson
- Department of Poultry Science, Texas A&M University, College Station, TX 77843-2472, USA
| | - A B McMullin
- Department of Poultry Science, Texas A&M University, College Station, TX 77843-2472, USA
| | - T Duong
- Department of Poultry Science, Texas A&M University, College Station, TX 77843-2472, USA
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25
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Abstract
Acinetobacter baumannii is characterized as a nosocomial, gram-negative, multidrug-resistant bacterium, which has gained increasing attention due to its prevalence in hospital settings and high mortality rates upon infection. Currently, a number of different protocols have been developed in attempts to genetically alter A. baumannii, including multidrug-resistant strains. Although the bacterium has an unusual ability to uptake exogenous DNA in the natural environments, within the laboratory setting, gene manipulation to study virulence properties can be challenging. In this chapter we describe a general protocol for modification of specific genes using homologous recombination and a counterselectable marker.
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Affiliation(s)
- Indranil Biswas
- Department of Microbiology, Molecular Genetics and Immunology, University of Kansas Medical Center, Kansas City, KS, USA.
| | - Joshua Mettlach
- Department of Microbiology, Molecular Genetics and Immunology, University of Kansas Medical Center, Kansas City, KS, USA
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26
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Ronish LA, Lillehoj E, Fields JK, Sundberg EJ, Piepenbrink KH. The structure of PilA from Acinetobacter baumannii AB5075 suggests a mechanism for functional specialization in Acinetobacter type IV pili. J Biol Chem 2018; 294:218-230. [PMID: 30413536 DOI: 10.1074/jbc.ra118.005814] [Citation(s) in RCA: 38] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2018] [Revised: 10/19/2018] [Indexed: 11/06/2022] Open
Abstract
Type IV pili (T4P) are bacterial appendages composed of protein subunits, called pilins, noncovalently assembled into helical fibers. T4P are essential, in many bacterial species, for processes as diverse as twitching motility, natural competence, biofilm or microcolony formation, and host cell adhesion. The genes encoding type IV pili are found universally in the Gram-negative, aerobic, nonflagellated, and pathogenic coccobacillus Acinetobacter baumannii, but there is considerable variation in PilA, the major protein subunit, both in amino acid sequence and in glycosylation patterns. Here we report the X-ray crystal structure of PilA from AB5075, a recently characterized, highly virulent isolate, at 1.9 Å resolution and compare it to homologues from A. baumannii strains ACICU and BIDMC57, which are C-terminally glycosylated. These structural comparisons revealed that PilAAB5075 exhibits a distinctly electronegative surface chemistry. To understand the functional consequences of this change in surface electrostatics, we complemented a ΔpilA knockout strain with divergent pilA genes from ACICU, BIDMC57, and AB5075. The resulting transgenic strains showed differential twitching motility and biofilm formation while maintaining the ability to adhere to epithelial cells. PilAAB5075 and PilAACICU, although structurally similar, promote different characteristics, favoring twitching motility and biofilm formation, respectively. These results support a model in which differences in pilus electrostatics affect the equilibrium of microcolony formation, which in turn alters the balance between motility and biofilm formation in Acinetobacter.
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Affiliation(s)
- Leslie A Ronish
- Department of Biochemistry, University of Nebraska-Lincoln, Lincoln, Nebraska 68588
| | - Erik Lillehoj
- Department of Pediatrics, University of Maryland School of Medicine, Baltimore, Maryland 21201
| | - James K Fields
- Institute of Human Virology, University of Maryland School of Medicine, Baltimore, Maryland 21201
| | - Eric J Sundberg
- Institute of Human Virology, University of Maryland School of Medicine, Baltimore, Maryland 21201; Department of Medicine, University of Maryland School of Medicine, Baltimore, Maryland 21201; Departments of Microbiology and Immunology, University of Maryland School of Medicine, Baltimore, Maryland 21201
| | - Kurt H Piepenbrink
- Department of Biochemistry, University of Nebraska-Lincoln, Lincoln, Nebraska 68588; Departments of Food Science and Technology, University of Nebraska-Lincoln, Lincoln, Nebraska 68588; Nebraska Food for Health Center, University of Nebraska-Lincoln, Lincoln, Nebraska 68588; Center for Integrated Biomolecular Communication, University of Nebraska-Lincoln, Lincoln, Nebraska 68588.
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27
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Gwin CM, Prakash N, Christian Belisario J, Haider L, Rosen ML, Martinez LR, Rigel NW. The apolipoprotein N-acyl transferase Lnt is dispensable for growth in Acinetobacter species. MICROBIOLOGY-SGM 2018; 164:1547-1556. [PMID: 30307391 DOI: 10.1099/mic.0.000726] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Directing the flow of protein traffic is a critical task faced by all cellular organisms. In Gram-negative bacteria, this traffic includes lipoproteins. Lipoproteins are synthesized as precursors in the cytoplasm and receive their acyl modifications upon export across the inner membrane. The third and final acyl chain is added by Lnt, which until recently was thought to be essential in all Gram-negatives. In this report, we show that Acinetobacter species can also tolerate a complete loss-of-function mutation in lnt. Absence of a fully functional Lnt impairs modification of lipoproteins, increases outer membrane permeability and susceptibility to antibiotics, and alters normal cellular morphology. In addition, we show that loss of lnt triggers a global transcriptional response to this added cellular stress. Taken together, our findings provide new insights on and support the growing revisions to the Gram-negative lipoprotein biogenesis paradigm.
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Affiliation(s)
- Celena M Gwin
- 1Department of Biology, Hofstra University, Hempstead, NY, USA.,2Department of Microbial Pathogenesis, Yale University, New Haven, CT, USA
| | - Natalia Prakash
- 1Department of Biology, Hofstra University, Hempstead, NY, USA
| | - J Christian Belisario
- 3Department of Biomedical Sciences, College of Osteopathic Medicine, New York Institute of Technology, Old Westbury, NY, USA
| | - Lubaina Haider
- 1Department of Biology, Hofstra University, Hempstead, NY, USA.,4College of Medicine, SUNY-Downstate Medical Center, Brooklyn, NY, USA
| | - Marlene L Rosen
- 1Department of Biology, Hofstra University, Hempstead, NY, USA
| | - Luis R Martinez
- 3Department of Biomedical Sciences, College of Osteopathic Medicine, New York Institute of Technology, Old Westbury, NY, USA.,5Department of Biological Sciences, The Border Biomedical Research Center, University of Texas at El Paso, El Paso, TX, USA
| | - Nathan W Rigel
- 1Department of Biology, Hofstra University, Hempstead, NY, USA
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28
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Crépin S, Ottosen EN, Peters K, Smith SN, Himpsl SD, Vollmer W, Mobley HLT. The lytic transglycosylase MltB connects membrane homeostasis and in vivo fitness of Acinetobacter baumannii. Mol Microbiol 2018; 109:745-762. [PMID: 29884996 PMCID: PMC6185781 DOI: 10.1111/mmi.14000] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2018] [Revised: 05/30/2018] [Accepted: 07/15/2018] [Indexed: 01/06/2023]
Abstract
Acinetobacter baumannii has emerged as a leading nosocomial pathogen, infecting a wide range of anatomic sites including the respiratory tract and the bloodstream. In addition to being multi‐drug resistant, little is known about the molecular basis of A. baumannii pathogenesis. To better understand A. baumannii virulence, a combination of a transposon‐sequencing (TraDIS) screen and the neutropenic mouse model of bacteremia was used to identify the full set of fitness genes required during bloodstream infection. The lytic transglycosylase MltB was identified as a critical fitness factor. MltB cleaves the MurNAc‐GlcNAc bond of peptidoglycan, which leads to cell wall remodeling. Here we show that MltB is part of a complex network connecting resistance to stresses, membrane homeostasis, biogenesis of pili and in vivo fitness. Indeed, inactivation of mltB not only impaired resistance to serum complement, cationic antimicrobial peptides and oxygen species, but also altered the cell envelope integrity, activated the envelope stress response, drastically reduced the number of pili at the cell surface and finally, significantly decreased colonization of both the bloodstream and the respiratory tract.
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Affiliation(s)
- Sébastien Crépin
- Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, MI, USA
| | - Elizabeth N Ottosen
- Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, MI, USA
| | - Katharina Peters
- Centre for Bacterial Cell Biology, Institute for Cell and Molecular Biosciences, Newcastle University, Newcastle upon Tyne, UK
| | - Sara N Smith
- Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, MI, USA
| | - Stephanie D Himpsl
- Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, MI, USA
| | - Waldemar Vollmer
- Centre for Bacterial Cell Biology, Institute for Cell and Molecular Biosciences, Newcastle University, Newcastle upon Tyne, UK
| | - Harry L T Mobley
- Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, MI, USA
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29
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Kandel PP, Chen H, De La Fuente L. A Short Protocol for Gene Knockout and Complementation in Xylella fastidiosa Shows that One of the Type IV Pilin Paralogs (PD1926) Is Needed for Twitching while Another (PD1924) Affects Pilus Number and Location. Appl Environ Microbiol 2018; 84:e01167-18. [PMID: 29980551 PMCID: PMC6121978 DOI: 10.1128/aem.01167-18] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2018] [Accepted: 06/29/2018] [Indexed: 11/20/2022] Open
Abstract
Twitching motility is one of the major virulence factors of the plant-pathogenic bacterium Xylella fastidiosa, and it is mediated by type IV pili (TFP) that are present at one of the cell poles. Genome analysis of X. fastidiosa showed the presence of at least four paralogs of the gene pilA, which encodes the TFP major pilin subunit. However, whether all of these paralogs have a functional role in TFP structure and function is unknown. Here, using a short and reliable protocol based on overlap extension PCR and natural transformation, deletion mutants of two pilA paralogs (pilA1 PD1924 and pilA2 PD1926) were generated in two X. fastidiosa subsp. fastidiosa strains, WM1-1 and TemeculaL, followed by assessment of twitching motility and biofilm formation. Deletion of pilA2 caused loss of twitching motility, whereas deletion of pilA1 did not influence twitching motility but caused hyperpiliation and extended distribution of TFP along the sides of the cell. Loss of twitching motility due to pilA2 deletion was restored when a wild-type copy of the pilA2 gene was added at a neutral site in the genome of mutants in both wild-type backgrounds. This study demonstrates that PCR templates generated by overlap extension PCR can be successfully used to rapidly generate gene knockouts and perform genetic complementation in X. fastidiosa, and that twitching motility in X. fastidiosa is controlled by regulating the transcription of the major pilin subunit, pilA2IMPORTANCE The bacterial plant pathogen Xylella fastidiosa causes incurable diseases in multiple hosts, including grape, citrus, and blueberry. Historically restricted to the Americas, it was recently found to cause epidemics in olives in Italy and to infect other hosts in Europe and Asia. In this study, we report a short protocol to create deletion and complemented mutants using fusion PCR and natural transformation. We also determined the distinct function of two pilin paralogs, the main structural component of TFP involved in twitching motility, which allows this bacterium to move inside the xylem vessels against the flow. One of the paralogs is needed for twitching movement, whereas the other does not have an effect on motility but influences the number and position of TFP. Since twitching motility is fundamental for the virulence of this xylem-limited bacterium, this study contributes to the understanding of the regulation of virulence by this pathogen.
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Affiliation(s)
- Prem P Kandel
- Department of Entomology and Plant Pathology, Auburn University, Auburn, Alabama, USA
| | - Hongyu Chen
- Department of Entomology and Plant Pathology, Auburn University, Auburn, Alabama, USA
| | - Leonardo De La Fuente
- Department of Entomology and Plant Pathology, Auburn University, Auburn, Alabama, USA
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30
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Functional Characterization of AbaQ, a Novel Efflux Pump Mediating Quinolone Resistance in Acinetobacter baumannii. Antimicrob Agents Chemother 2018; 62:AAC.00906-18. [PMID: 29941648 DOI: 10.1128/aac.00906-18] [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: 05/04/2018] [Accepted: 06/18/2018] [Indexed: 01/15/2023] Open
Abstract
Acinetobacter baumannii has emerged as an important multidrug-resistant nosocomial pathogen. In previous work, we identified a putative MFS transporter, AU097_RS17040, involved in the pathogenicity of A. baumannii (M. Pérez-Varela, J. Corral, J. A. Vallejo, S. Rumbo-Feal, G. Bou, J. Aranda, and J. Barbé, Infect Immun 85:e00327-17, 2017, https://doi.org/10.1128/IAI.00327-17). In this study, we analyzed the susceptibility to diverse antimicrobial agents of A. baumannii cells defective in this transporter, referred to as AbaQ. Our results showed that AbaQ is mainly involved in the extrusion of quinolone-type drugs in A. baumannii.
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31
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Identification of Novel Acinetobacter baumannii Type VI Secretion System Antibacterial Effector and Immunity Pairs. Infect Immun 2018; 86:IAI.00297-18. [PMID: 29735524 DOI: 10.1128/iai.00297-18] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2018] [Accepted: 05/04/2018] [Indexed: 12/21/2022] Open
Abstract
The type VI secretion system (T6SS) is a macromolecular machine that delivers protein effectors into host cells and/or competing bacteria. The effectors may be delivered as noncovalently bound cargo of T6SS needle proteins (VgrG/Hcp/PAAR) or as C-terminal extensions of these proteins. Many Acinetobacter baumannii strains produce a T6SS, but little is known about the specific effectors or how they are delivered. In this study, we show that A. baumannii AB307-0294 encodes three vgrG loci, each containing a vgrG gene, a T6SS toxic effector gene, and an antitoxin/immunity gene. Each of the T6SS toxic effectors could kill Escherichia coli when produced in trans unless the cognate immunity protein was coproduced. To determine the role of each VgrG in effector delivery, we performed interbacterial competitive killing assays using A. baumannii AB307-0294 vgrG mutants, together with Acinetobacter baylyi prey cells expressing pairs of immunity genes that protected against two toxic effectors but not a third. Using this approach, we showed that AB307-0294 produces only three T6SS toxic effectors capable of killing A. baylyi and that each VgrG protein is specific for the carriage of one effector. Finally, we analyzed a number of A. baumannii genomes and identified significant diversity in the range of encoded T6SS VgrG and effector proteins, with correlations between effector types and A. baumannii global clone lineages.
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32
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Contact-Dependent Growth Inhibition Proteins in Acinetobacter baylyi ADP1. Curr Microbiol 2018; 75:1434-1440. [PMID: 30019131 PMCID: PMC6182759 DOI: 10.1007/s00284-018-1540-y] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2018] [Accepted: 07/12/2018] [Indexed: 02/08/2023]
Abstract
Bacterial contact-dependent growth inhibition (CDI) systems are two-partner secretion systems in which toxic CdiA proteins are exported on the outer membrane by cognate transporter CdiB proteins. Upon binding to specific receptors, the C-terminal toxic (CT) domain, detached from CdiA, is delivered to neighbouring cells. Contacts inhibit the growth of not-self-bacteria, lacking immunity proteins co-expressed with CdiA, but promote cooperative behaviours in "self" bacteria, favouring the formation of biofilm structures. The Acinetobacter baylyi ADP1 strain features two CdiA, which differ significantly in size and have different CT domains. Homologous proteins sharing the same CT domains have been identified in A. baumannii. The growth inhibition property of the two A. baylyi CdiA proteins was supported by competition assays between wild-type cells and mutants lacking immunity genes. However, neither protein plays a role in biofilm formation or adherence to epithelial cells, as proved by assays carried out with knockout mutants. Inhibitory and stimulatory properties may be similarly uncoupled in A. baumannii proteins.
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33
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Emergence of High-Level Colistin Resistance in an Acinetobacter baumannii Clinical Isolate Mediated by Inactivation of the Global Regulator H-NS. Antimicrob Agents Chemother 2018; 62:AAC.02442-17. [PMID: 29712662 DOI: 10.1128/aac.02442-17] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2017] [Accepted: 03/01/2018] [Indexed: 12/31/2022] Open
Abstract
Colistin is a crucial last-line drug used for the treatment of life-threatening infections caused by multidrug-resistant strains of the Gram-negative bacterium Acinetobacter baumannii However, colistin-resistant A. baumannii isolates can still be isolated following failed colistin therapy. Resistance is most often mediated by the addition of phosphoethanolamine (pEtN) to lipid A by PmrC, following missense mutations in the pmrCAB operon encoding PmrC and the two-component signal transduction system PmrA/PmrB. We recovered a pair of A. baumannii isolates from a single patient before (6009-1) and after (6009-2) failed colistin treatment. These strains displayed low and very high levels of colistin resistance (MICs, 8 to 16 μg/ml and 128 μg/ml), respectively. To understand how increased colistin resistance arose, we sequenced the genome of each isolate, which revealed that 6009-2 had an extra copy of the insertion sequence element ISAba125 within a gene encoding an H-NS family transcriptional regulator. To confirm the role of H-NS in colistin resistance, we generated an hns deletion mutant in 6009-1 and showed that colistin resistance increased upon the deletion of hns We also provided 6009-2 with an intact copy of hns and showed that the strain was no longer resistant to high concentrations of colistin. Transcriptomic analysis of the clinical isolates identified more than 150 genes as being differentially expressed in the colistin-resistant hns mutant 6009-2. Importantly, the expression of eptA, encoding a second lipid A-specific pEtN transferase but not pmrC, was increased in the hns mutant. This is the first time an H-NS family transcriptional regulator has been associated with a pEtN transferase and colistin resistance.
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New Shuttle Vectors for Gene Cloning and Expression in Multidrug-Resistant Acinetobacter Species. Antimicrob Agents Chemother 2018; 62:AAC.02480-17. [PMID: 29339383 DOI: 10.1128/aac.02480-17] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2017] [Accepted: 01/02/2018] [Indexed: 12/28/2022] Open
Abstract
Understanding bacterial pathogenesis requires adequate genetic tools to assess the role of individual virulence determinants by mutagenesis and complementation assays, as well as for homologous and heterologous expression of cloned genes. Our knowledge of Acinetobacter baumannii pathogenesis has so far been limited by the scarcity of genetic tools to manipulate multidrug-resistant (MDR) epidemic strains, which are responsible for most infections. Here, we report on the construction of new multipurpose shuttle plasmids, namely, pVRL1 and pVRL2, which can efficiently replicate in Acinetobacter spp. and in Escherichia coli The pVRL1 plasmid has been constructed by combining (i) the cryptic plasmid pWH1277 from Acinetobacter calcoaceticus, which provides an origin of replication for Acinetobacter spp.; (ii) a ColE1-like origin of replication; (iii) the gentamicin or zeocin resistance cassette for antibiotic selection; and (iv) a multilinker containing several unique restriction sites. Modification of pVRL1 led to the generation of the pVRL2 plasmid, which allows arabinose-inducible gene transcription with an undetectable basal expression level of cloned genes under uninduced conditions and a high dynamic range of responsiveness to the inducer. Both pVRL1 and pVRL2 can easily be selected in MDR A. baumannii, have a narrow host range and a high copy number, are stably maintained in Acinetobacter spp., and appear to be compatible with indigenous plasmids carried by epidemic strains. Plasmid maintenance is guaranteed by the presence of a toxin-antitoxin system, providing more insights into the mechanism of plasmid stability in Acinetobacter spp.
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Quinn B, Traglia GM, Nguyen M, Martinez J, Liu C, Fernandez JS, Ramirez MS. Effect of Host Human Products on Natural Transformation in Acinetobacter baumannii. Curr Microbiol 2018; 76:950-953. [PMID: 29332139 DOI: 10.1007/s00284-017-1417-5] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2017] [Accepted: 12/06/2017] [Indexed: 12/15/2022]
Abstract
Our previous data show that serum albumin can trigger natural transformation in Acinetobacter baumannii. However, extracellular matrix/basal membrane components, norepinephrine, and mucin did not have a significant effect on this process. Therefore, the effect of human products appears to be albumin specific, as both BSA and HSA have been shown to increase of natural transformation.
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Affiliation(s)
- Brettni Quinn
- Center for Applied Biotechnology Studies, Department of Biological Science, College of Natural Sciences and Mathematics, California State University Fullerton, Fullerton, CA, USA
| | - German M Traglia
- Laboratorio de Bacteriología Clínica, Departamento de Bioquímica Clínica, Facultad de Farmacia y Bioquímica, Hospital de Clínicas José de San Martín, Buenos Aires, Argentina
| | - Meaghan Nguyen
- Center for Applied Biotechnology Studies, Department of Biological Science, College of Natural Sciences and Mathematics, California State University Fullerton, Fullerton, CA, USA
| | - Jasmine Martinez
- Center for Applied Biotechnology Studies, Department of Biological Science, College of Natural Sciences and Mathematics, California State University Fullerton, Fullerton, CA, USA
| | - Christine Liu
- Center for Applied Biotechnology Studies, Department of Biological Science, College of Natural Sciences and Mathematics, California State University Fullerton, Fullerton, CA, USA
| | - Jennifer S Fernandez
- Center for Applied Biotechnology Studies, Department of Biological Science, College of Natural Sciences and Mathematics, California State University Fullerton, Fullerton, CA, USA
| | - Maria Soledad Ramirez
- Center for Applied Biotechnology Studies, Department of Biological Science, College of Natural Sciences and Mathematics, California State University Fullerton, Fullerton, CA, USA.
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Kuo HY, Chao HH, Liao PC, Hsu L, Chang KC, Tung CH, Chen CH, Liou ML. Functional Characterization of Acinetobacter baumannii Lacking the RNA Chaperone Hfq. Front Microbiol 2017; 8:2068. [PMID: 29163381 PMCID: PMC5663733 DOI: 10.3389/fmicb.2017.02068] [Citation(s) in RCA: 38] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2017] [Accepted: 10/09/2017] [Indexed: 12/15/2022] Open
Abstract
The RNA chaperone Hfq is involved in the riboregulation of diverse genes via small RNAs. Recent studies have demonstrated that Hfq contributes to the stress response and the virulence of several pathogens, and the roles of Hfq vary among bacterial species. Here, we attempted to elucidate the role of Hfq in Acinetobacter baumannii ATCC 17978. In the absence of hfq, A. baumannii exhibited retarded cell growth and was highly sensitive to environmental stress, including osmotic and oxidative pressure, pH, and temperature. Compared to the wild-type, the Hfq mutant had reduced outer membrane vesicles secretion and fimbriae production as visualized by atomic force microscopy. The absence of hfq reduced biofilm formation, airway epithelial cell adhesion and invasion, and survival in macrophage. Further, the hfq mutant induced significantly higher IL-8 levels in airway epithelial cells, which would promote bacterial clearance by the host. In addition to results similar to those reported for other bacteria, our findings demonstrate that Hfq is required in the regulation of the iron-acquisition system via downregulating the bauA and basD genes, the stress-related outer membrane proteins carO, A1S_0820, ompA, and nlpE, and the stress-related cytosolic proteins uspA and groEL. Our data indicate that Hfq plays a critical role in environmental adaptation and virulence in A. baumannii by modulating stress responses, surface architectures, and virulence factors. This study is the first to illustrate the functional role of Hfq in A. baumannii.
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Affiliation(s)
- Han-Yueh Kuo
- Department of Medicine, National Taiwan University Hospital Hsin-Chu Branch, Hsinchu, Taiwan.,Department of Internal Medicine, College of Medicine, National Taiwan University, Taipei, Taiwan
| | - Hsuan-Hao Chao
- Department of Electrophysics, National Chiao Tung University, Hsinchu, Taiwan
| | - Po-Cheng Liao
- Department of Medical Laboratory Science and Biotechnology, Yuanpei University, Hsinchu, Taiwan
| | - Long Hsu
- Department of Electrophysics, National Chiao Tung University, Hsinchu, Taiwan
| | - Kai-Chih Chang
- Department of Laboratory Medicine and Biotechnology, Tzu Chi University, Hualien, Taiwan
| | - Chi-Hua Tung
- Department of Bioinformatics, Chung Hua University, Hsinchu, Taiwan
| | - Chang-Hua Chen
- Division of Infectious Disease, Department of Internal Medicine, Changhua Christian Hospital, Changhua, Taiwan.,Center of Infection Prevention and Control, Changhua Christian Hospital, Changhua, Taiwan
| | - Ming-Li Liou
- Department of Medical Laboratory Science and Biotechnology, Yuanpei University, Hsinchu, Taiwan
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Activity of the β-Lactamase Inhibitor LN-1-255 against Carbapenem-Hydrolyzing Class D β-Lactamases from Acinetobacter baumannii. Antimicrob Agents Chemother 2017; 61:AAC.01172-17. [PMID: 28807908 DOI: 10.1128/aac.01172-17] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2017] [Accepted: 08/02/2017] [Indexed: 12/21/2022] Open
Abstract
The number of infections caused by Gram-negative pathogens carrying carbapenemases is increasing, and the group of carbapenem-hydrolyzing class D β-lactamases (CHDLs) is especially problematic. Several clinically important CHDLs have been identified in Acinetobacter baumannii, including OXA-23, OXA-24/40, OXA-58, OXA-143, OXA-235, and the chromosomally encoded OXA-51. The selection and dissemination of carbapenem-resistant A. baumannii strains constitutes a serious global threat. Carbapenems have been successfully utilized as last-resort antibiotics for the treatment of multidrug-resistant A. baumannii infections. However, the spread of OXA carbapenemases is compromising the continued use of these antimicrobials. In response to this clinical issue, it is necessary and urgent to design and develop new specific inhibitors with efficacy against these enzymes. The aim of this work was to characterize the inhibitory activity of LN-1-255 (a 6-alkylidene-2-substituted penicillin sulfone) and compare it to that of two established inhibitors (avibactam and tazobactam) against the most relevant enzymes of each group of class D carbapenemases in A. baumannii The β-lactamase inhibitor LN-1-255 demonstrated excellent microbiological synergy and inhibition kinetics parameters against all tested CHDLs and a significantly higher activity than tazobactam and avibactam. A combination of carbapenems and LN-1-255 was effective against A. baumannii class D carbapenemases. Docking assays confirmed the affinity of LN-1-255 for the active site of these enzymes. LN-1-255 represents a potential new β-lactamase inhibitor that may have a significant role in eradicating infections caused by A. baumannii isolates carrying CHDLs.
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Álvarez-Fraga L, Rumbo-Feal S, Pérez A, Gómez MJ, Gayoso C, Vallejo JA, Ohneck EJ, Valle J, Actis LA, Beceiro A, Bou G, Poza M. Global assessment of small RNAs reveals a non-coding transcript involved in biofilm formation and attachment in Acinetobacter baumannii ATCC 17978. PLoS One 2017; 12:e0182084. [PMID: 28763494 PMCID: PMC5538643 DOI: 10.1371/journal.pone.0182084] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2017] [Accepted: 07/12/2017] [Indexed: 12/30/2022] Open
Abstract
Many strains of Acinetobacter baumannii have been described as being able to form biofilm. Small non-coding RNAs (sRNAs) control gene expression in many regulatory circuits in bacteria. The aim of the present work was to provide a global description of the sRNAs produced both by planktonic and biofilm-associated (sessile) cells of A. baumannii ATCC 17978, and to compare the corresponding gene expression profiles to identify sRNAs molecules associated to biofilm formation and virulence. sRNA was extracted from both planktonic and sessile cells and reverse transcribed. cDNA was subjected to 454-pyrosequencing using the GS-FLX Titanium chemistry. The global analysis of the small RNA transcriptome revealed different sRNA expression patterns in planktonic and biofilm associated cells, with some of the transcripts only expressed or repressed in sessile bacteria. A total of 255 sRNAs were detected, with 185 of them differentially expressed in the different types of cells. A total of 9 sRNAs were expressed only in biofilm cells, while the expression of other 21 coding regions were repressed only in biofilm cells. Strikingly, the expression level of the sRNA 13573 was 120 times higher in biofilms than in planktonic cells, an observation that prompted us to further investigate the biological role of this non-coding transcript. Analyses of an isogenic mutant and over-expressing strains revealed that the sRNA 13573 gene is involved in biofilm formation and attachment to A549 human alveolar epithelial cells. The present work serves as a basis for future studies examining the complex regulatory network that regulate biofilm biogenesis and attachment to eukaryotic cells in A. baumannii ATCC 17978.
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Affiliation(s)
- Laura Álvarez-Fraga
- Departamento de Microbiología, Instituto de Investigación Biomédica (INIBIC), Complejo Hospitalario Universitario (CHUAC), A Coruña, Spain
| | - Soraya Rumbo-Feal
- Departamento de Microbiología, Instituto de Investigación Biomédica (INIBIC), Complejo Hospitalario Universitario (CHUAC), A Coruña, Spain
| | - Astrid Pérez
- Departamento de Microbiología, Instituto de Investigación Biomédica (INIBIC), Complejo Hospitalario Universitario (CHUAC), A Coruña, Spain
- Department of Microbiology, Miami University, Oxford, Ohio, United States of America
| | - Manuel J. Gómez
- Department of Molecular Evolution, Center for Astrobiology, INTA-CSIC, Torrejón de Ardoz, Madrid, Spain
- Centro Nacional de Investigaciones Cardiovasculares Carlos III, Madrid, Spain
| | - Carmen Gayoso
- Departamento de Microbiología, Instituto de Investigación Biomédica (INIBIC), Complejo Hospitalario Universitario (CHUAC), A Coruña, Spain
| | - Juan A. Vallejo
- Departamento de Microbiología, Instituto de Investigación Biomédica (INIBIC), Complejo Hospitalario Universitario (CHUAC), A Coruña, Spain
| | - Emily J. Ohneck
- Department of Microbiology, Miami University, Oxford, Ohio, United States of America
| | - Jaione Valle
- Departamento de Biofilms Microbianos, Instituto de Agrobiotecnología, Navarra, Spain
| | - Luis A. Actis
- Department of Microbiology, Miami University, Oxford, Ohio, United States of America
| | - Alejandro Beceiro
- Departamento de Microbiología, Instituto de Investigación Biomédica (INIBIC), Complejo Hospitalario Universitario (CHUAC), A Coruña, Spain
| | - Germán Bou
- Departamento de Microbiología, Instituto de Investigación Biomédica (INIBIC), Complejo Hospitalario Universitario (CHUAC), A Coruña, Spain
- * E-mail: (GB); (MP)
| | - Margarita Poza
- Departamento de Microbiología, Instituto de Investigación Biomédica (INIBIC), Complejo Hospitalario Universitario (CHUAC), A Coruña, Spain
- * E-mail: (GB); (MP)
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Mutations in the β-Subunit of the RNA Polymerase Impair the Surface-Associated Motility and Virulence of Acinetobacter baumannii. Infect Immun 2017; 85:IAI.00327-17. [PMID: 28507065 DOI: 10.1128/iai.00327-17] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2017] [Accepted: 05/08/2017] [Indexed: 12/19/2022] Open
Abstract
Acinetobacter baumannii is a major cause of antibiotic-resistant nosocomial infections worldwide. In this study, several rifampin-resistant spontaneous mutants obtained from the A. baumannii ATCC 17978 strain that differed in their point mutations in the rpoB gene, encoding the β-subunit of the RNA polymerase, were isolated. All the mutants harboring amino acid substitutions in position 522 or 540 of the RpoB protein were impaired in surface-associated motility and had attenuated virulence in the fertility model of Caenorhabditis elegans The transcriptional profile of these mutants included six downregulated genes encoding proteins homologous to transporters and metabolic enzymes widespread among A. baumannii clinical isolates. The construction of knockout mutants in each of the six downregulated genes revealed a significant reduction in the surface-associated motility and virulence of four of them in the A. baumannii ATCC 17978 strain, as well as in the virulent clinical isolate MAR002. Taken together, our results provide strong evidence of the connection between motility and virulence in this multiresistant nosocomial pathogen.
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Selectable Markers for Use in Genetic Manipulation of Extensively Drug-Resistant (XDR) Acinetobacter baumannii HUMC1. mSphere 2017; 2:mSphere00140-17. [PMID: 28497114 PMCID: PMC5422034 DOI: 10.1128/msphere.00140-17] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2017] [Accepted: 04/06/2017] [Indexed: 11/20/2022] Open
Abstract
Multidrug-resistant (MDR), extensively drug-resistant (XDR), and pan-drug-resistant (PDR) strains of Acinetobacter baumannii have frequently been characterized. The ability of A. baumannii to develop resistance to antibiotics is a key reason this organism has been difficult to study using genetic and molecular biology approaches. Here we report selectable markers that are not only useful but necessary for the selection of drug-resistant transformants in the setting of drug-resistant backgrounds. Use of these selectable markers can be applied to a variety of genetic and molecular techniques such as mutagenesis and transformation. These selectable markers will help promote genetic and molecular biology studies of otherwise onerous drug-resistant strains, while avoiding the generation of pathogenic organisms that are resistant to clinically relevant antibiotics. Acinetobacter baumannii is one of the most antibiotic-resistant pathogens in clinical medicine, and extensively drug-resistant (XDR) strains are commonly isolated from infected patients. Such XDR strains are already resistant to traditional selectable genetic markers, limiting the ability to conduct pathogenesis research by genetic disruption. Optimization of selectable markers is therefore critical for the advancement of fundamental molecular biology techniques to use in these strains. We screened 23 drugs that constitute a broad array of antibiotics spanning multiple drug classes against HUMC1, a highly virulent and XDR A. baumannii clinical blood and lung isolate. HUMC1 is resistant to all clinically useful antibiotics that are reported by the clinical microbiology laboratory, except for colistin. Ethical concerns about intentionally establishing pan-resistance, including to the last-line agent, colistin, in a clinical isolate made identification of other markers desirable. We screened additional antibiotics that are in clinical use and those that are useful only in a lab setting to identify selectable markers that were effective at selecting for transformants in vitro. We show that supraphysiological levels of tetracycline can overcome innate drug resistance displayed by this XDR strain. Last, we demonstrate that transformation of the tetA (tetracycline resistance) and Sh ble (zeocin resistance), but not pac (puromycin resistance), resistance cassettes allow for selection of drug-resistant transformants. These results make the genetic manipulation of XDR A. baumannii strains easily achieved. IMPORTANCE Multidrug-resistant (MDR), extensively drug-resistant (XDR), and pan-drug-resistant (PDR) strains of Acinetobacter baumannii have frequently been characterized. The ability of A. baumannii to develop resistance to antibiotics is a key reason this organism has been difficult to study using genetic and molecular biology approaches. Here we report selectable markers that are not only useful but necessary for the selection of drug-resistant transformants in the setting of drug-resistant backgrounds. Use of these selectable markers can be applied to a variety of genetic and molecular techniques such as mutagenesis and transformation. These selectable markers will help promote genetic and molecular biology studies of otherwise onerous drug-resistant strains, while avoiding the generation of pathogenic organisms that are resistant to clinically relevant antibiotics.
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Saranathan R, Pagal S, Sawant AR, Tomar A, Madhangi M, Sah S, Satti A, Arunkumar KP, Prashanth K. Disruption of tetR type regulator adeN by mobile genetic element confers elevated virulence in Acinetobacter baumannii. Virulence 2017; 8:1316-1334. [PMID: 28436748 DOI: 10.1080/21505594.2017.1322240] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
Acinetobacter baumannii is an important human pathogen and considered as a major threat due to its extreme drug resistance. In this study, the genome of a hyper-virulent MDR strain PKAB07 of A. baumannii isolated from an Indian patient was sequenced and analyzed to understand its mechanisms of virulence, resistance and evolution. Comparative genome analysis of PKAB07 revealed virulence and resistance related genes scattered throughout the genome, instead of being organized as an island, indicating the highly mosaic nature of the genome. Many intermittent horizontal gene transfer events, insertion sequence (IS) element insertions identified were augmenting resistance machinery and elevating the SNP densities in A. baumannii eventually aiding in their swift evolution. ISAba1, the most widely distributed insertion sequence in A. baumannii was found in multiple sites in PKAB07. Out of many ISAba1 insertions, we identified novel insertions in 9 different genes wherein insertional inactivation of adeN (tetR type regulator) was significant. To assess the significance of this disruption in A. baumannii, adeN mutant and complement strains were constructed in A. baumannii ATCC 17978 strain and studied. Biofilm levels were abrogated in the adeN knockout when compared with the wild type and complemented strain of adeN knockout. Virulence of the adeN knockout mutant strain was observed to be high, which was validated by in vitro experiments and Galleria mellonella infection model. The overexpression of adeJ, a major component of AdeIJK efflux pump observed in adeN knockout strain could be the possible reason for the elevated virulence in adeN mutant and PKB07 strain. Knocking out of adeN in ATCC strain led to increased resistance and virulence at par with the PKAB07. Disruption of tetR type regulator adeN by ISAba1 consequently has led to elevated virulence in this pathogen.
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Affiliation(s)
- Rajagopalan Saranathan
- a Department of Biotechnology, School of Life Sciences , Pondicherry University , Puducherry , India
| | - Sudhakar Pagal
- a Department of Biotechnology, School of Life Sciences , Pondicherry University , Puducherry , India
| | - Ajit R Sawant
- a Department of Biotechnology, School of Life Sciences , Pondicherry University , Puducherry , India
| | - Archana Tomar
- b Laboratory of Molecular Genetics , Centre for DNA Fingerprinting and Diagnostics (CDFD) , Hyderabad , India
| | - M Madhangi
- a Department of Biotechnology, School of Life Sciences , Pondicherry University , Puducherry , India
| | - Suresh Sah
- a Department of Biotechnology, School of Life Sciences , Pondicherry University , Puducherry , India
| | - Annapurna Satti
- b Laboratory of Molecular Genetics , Centre for DNA Fingerprinting and Diagnostics (CDFD) , Hyderabad , India
| | - K P Arunkumar
- b Laboratory of Molecular Genetics , Centre for DNA Fingerprinting and Diagnostics (CDFD) , Hyderabad , India
| | - K Prashanth
- a Department of Biotechnology, School of Life Sciences , Pondicherry University , Puducherry , India
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Serum Albumin and Ca2+ Are Natural Competence Inducers in the Human Pathogen Acinetobacter baumannii. Antimicrob Agents Chemother 2016; 60:4920-9. [PMID: 27270286 DOI: 10.1128/aac.00529-16] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2016] [Accepted: 05/28/2016] [Indexed: 01/07/2023] Open
Abstract
The increasing frequency of bacteria showing antimicrobial resistance (AMR) raises the menace of entering into a postantibiotic era. Horizontal gene transfer (HGT) is one of the prime reasons for AMR acquisition. Acinetobacter baumannii is a nosocomial pathogen with outstanding abilities to survive in the hospital environment and to acquire resistance determinants. Its capacity to incorporate exogenous DNA is a major source of AMR genes; however, few studies have addressed this subject. The transformation machinery as well as the factors that induce natural competence in A. baumannii are unknown. In this study, we demonstrate that naturally competent strain A118 increases its natural transformation frequency upon the addition of Ca(2+)or albumin. We show that comEA and pilQ are involved in this process since their expression levels are increased upon the addition of these compounds. An unspecific protein, like casein, does not reproduce this effect, showing that albumin's effect is specific. Our work describes the first specific inducers of natural competence in A. baumannii Overall, our results suggest that the main protein in blood enhances HGT in A. baumannii, contributing to the increase of AMR in this threatening human pathogen.
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Li X, Quan J, Yang Y, Ji J, Liu L, Fu Y, Hua X, Chen Y, Pi B, Jiang Y, Yu Y. Abrp, a new gene, confers reduced susceptibility to tetracycline, glycylcine, chloramphenicol and fosfomycin classes in Acinetobacter baumannii. Eur J Clin Microbiol Infect Dis 2016; 35:1371-5. [PMID: 27220329 DOI: 10.1007/s10096-016-2674-0] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2015] [Accepted: 05/09/2016] [Indexed: 11/29/2022]
Abstract
Acinetobacter baumannii, a non-fermenting gram-negative coccobacillus, is a major pathogen responsible for a variety of healthcare-associated infections, including pneumonia, urinary tract and bloodstream infections. Moreover, A. baumannii is associated with alarming increases in drug resistance rates to almost all available antibiotics leaving limited treatment options. Here, we characterize the biological functions of a novel gene, abrp, which encodes a peptidase C13 family. We demonstrate that the abrp is associated with decreased susceptibility to tetracycline, minocycline, doxycycline, tigecycline, chloramphenicol and fosfomycin. Deletion of abrp was able to increase cell membrane permeability and display slower cell growth rate. Results from the present study show that abrp plays an important role in conferring reduced susceptibility to different classes of antibiotics and cell growth in A. baumannii. The change of antibiotic sensitivities may result from modifications to the cell membrane permeability of A. baumannii.
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Affiliation(s)
- X Li
- Department of Infectious Diseases, Sir Run Run Shaw Hospital, College of Medicine, Zhejiang University, Hangzhou, Zhejiang, 310016, China.,Centre of Laboratory Medicine, Zhejiang Provincial People's Hospital, 158 Shangtang Road, Hangzhou, 310014, China
| | - J Quan
- Department of Infectious Diseases, Sir Run Run Shaw Hospital, College of Medicine, Zhejiang University, Hangzhou, Zhejiang, 310016, China
| | - Y Yang
- Department of Infectious Diseases, Sir Run Run Shaw Hospital, College of Medicine, Zhejiang University, Hangzhou, Zhejiang, 310016, China
| | - J Ji
- Department of Infectious Diseases, Sir Run Run Shaw Hospital, College of Medicine, Zhejiang University, Hangzhou, Zhejiang, 310016, China
| | - L Liu
- Department of Infectious Diseases, Sir Run Run Shaw Hospital, College of Medicine, Zhejiang University, Hangzhou, Zhejiang, 310016, China
| | - Y Fu
- Department of Infectious Diseases, Sir Run Run Shaw Hospital, College of Medicine, Zhejiang University, Hangzhou, Zhejiang, 310016, China
| | - X Hua
- Department of Infectious Diseases, Sir Run Run Shaw Hospital, College of Medicine, Zhejiang University, Hangzhou, Zhejiang, 310016, China
| | - Y Chen
- Department of Infectious Diseases, Sir Run Run Shaw Hospital, College of Medicine, Zhejiang University, Hangzhou, Zhejiang, 310016, China
| | - B Pi
- Department of Infectious Diseases, Sir Run Run Shaw Hospital, College of Medicine, Zhejiang University, Hangzhou, Zhejiang, 310016, China
| | - Y Jiang
- Department of Infectious Diseases, Sir Run Run Shaw Hospital, College of Medicine, Zhejiang University, Hangzhou, Zhejiang, 310016, China
| | - Y Yu
- Department of Infectious Diseases, Sir Run Run Shaw Hospital, College of Medicine, Zhejiang University, Hangzhou, Zhejiang, 310016, China.
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Characterization of surface antigen protein 1 (SurA1) from Acinetobacter baumannii and its role in virulence and fitness. Vet Microbiol 2016; 186:126-38. [PMID: 27016767 DOI: 10.1016/j.vetmic.2016.02.018] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2015] [Revised: 01/24/2016] [Accepted: 02/22/2016] [Indexed: 01/02/2023]
Abstract
Acinetobacter baumannii is a Gram-negative bacillus that causes nosocomial infections, such as bacteremia, pneumonia, and meningitis and urinary tract and wound infections. In the present study, the surface antigen protein 1 (SurA1) gene of A. baumannii strain CCGGD201101 was identified, cloned and expressed, and then its roles in fitness and virulence were investigated. Virulence was observed in the human lung cancer cell lines A549 and HEp-2 at one week after treatment with recombinant SurA1. One isogenic SurA1 knock-out strain, GR0015, which was derived from the A. baumannii strain CCGGD201101 isolated from diseased chicks in a previous study, highlighted the effect of SurA1 on fitness and growth. Its growth rate in LB broth and killing activity in human sera were significantly decreased compared with strain CCGGD201101. In the Galleria mellonella insect model, the isogenic SurA1 knock-out strain exhibited a lower survival rate and decreased dissemination. These results suggest that SurA1 plays an important role in the fitness and virulence of A. baumannii.
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Yildirim S, Thompson MG, Jacobs AC, Zurawski DV, Kirkup BC. Evaluation of Parameters for High Efficiency Transformation of Acinetobacter baumannii. Sci Rep 2016; 6:22110. [PMID: 26911658 PMCID: PMC4766488 DOI: 10.1038/srep22110] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2015] [Accepted: 02/03/2016] [Indexed: 11/09/2022] Open
Abstract
Acinetobacter baumannii is an emerging, nosocomial pathogen that is poorly characterized due to a paucity of genetic tools and methods. While whole genome sequence data from several epidemic and environmental strains have recently become available, the functional characterization of genes is significantly lagging. Efficient transformation is one of the first steps to develop molecular tools that can be used to address these shortcomings. Here we report parameters allowing high efficiency transformation of A. baumannii. Using a multi-factorial experimental design we found that growth phase, voltage, and resistance all significantly contribute to transformation efficiency. The highest efficiency (4.3 × 10(8) Transformants/μg DNA) was obtained at the stationary growth phase of the bacterium (OD 6.0) using 25 ng of plasmid DNA under 100 Ohms resistance and 1.7 kV/cm voltage. The optimized electroporation parameters reported here provide a useful tool for genetic manipulation of A. baumannii.
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Affiliation(s)
- Suleyman Yildirim
- Department of Wound Infections, Bacterial Diseases Walter Reed Army Institute of Research, Silver Spring, Maryland, USA
| | - Mitchell G Thompson
- Department of Wound Infections, Bacterial Diseases Walter Reed Army Institute of Research, Silver Spring, Maryland, USA
| | - Anna C Jacobs
- Department of Wound Infections, Bacterial Diseases Walter Reed Army Institute of Research, Silver Spring, Maryland, USA
| | - Daniel V Zurawski
- Department of Wound Infections, Bacterial Diseases Walter Reed Army Institute of Research, Silver Spring, Maryland, USA
| | - Benjamin C Kirkup
- Department of Wound Infections, Bacterial Diseases Walter Reed Army Institute of Research, Silver Spring, Maryland, USA.,Department of Medicine, Infectious Diseases Division, Uniformed Services University of the Health Sciences, F. Edward Hebert School of Medicine, Bethesda, Maryland, USA
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Catel-Ferreira M, Marti S, Guillon L, Jara L, Coadou G, Molle V, Bouffartigues E, Bou G, Shalk I, Jouenne T, Vila-Farrés X, Dé E. The outer membrane porin OmpW of Acinetobacter baumannii is involved in iron uptake and colistin binding. FEBS Lett 2016; 590:224-31. [PMID: 26823169 DOI: 10.1002/1873-3468.12050] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2015] [Revised: 12/10/2015] [Indexed: 11/07/2022]
Abstract
This study was undertaken to characterize functions of the outer membrane protein OmpW, which potentially contributes to the development of colistin- and imipenem-resistance in Acinetobacter baumannii. Reconstitution of OmpW in artificial lipid bilayers showed that it forms small channels (23 pS in 1 m KCl) and markedly interacts with iron and colistin, but not with imipenem. In vivo, (55) Fe uptake assays comparing the behaviours of ΔompW mutant and wild-type strains confirmed a role for OmpW in A. baumannii iron homeostasis. However, the loss of OmpW expression did not have an impact on A. baumannii susceptibilities to colistin or imipenem.
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Affiliation(s)
- Manuella Catel-Ferreira
- CNRS UMR 6270 & FR3038, Normandie Univ, Laboratoire Polymères, Biopolymères & Surfaces, Université de Rouen, Mont Saint Aignan, France
| | - Sara Marti
- CNRS UMR 6270 & FR3038, Normandie Univ, Laboratoire Polymères, Biopolymères & Surfaces, Université de Rouen, Mont Saint Aignan, France.,Center for International Health Research, CRESIB, Hospital Clínic, University of Barcelona, Spain
| | - Laurent Guillon
- UMR 7242, Université de Strasbourg-CNRS, ESBS, Illkirch, France
| | - Luis Jara
- Departament de Genètica i Microbiologia, Facultat de Biociències, Universitat Autònoma de Barcelona, Spain
| | - Gaël Coadou
- COBRA-CNRS, Laboratoire de RMN et Modélisation moléculaire, UMR 6014 & FR3038 CNRS, Université de Rouen, Mont Saint Aignan, France
| | - Virginie Molle
- Laboratoire de Dynamique des Interactions Membranaires Normales et Pathologiques, Universités de Montpellier II et I, CNRS; UMR 5235, Montpellier Cedex 05, France
| | - Emeline Bouffartigues
- Laboratoire de Microbiologie Signaux et Micro-Environnement (LMSM) EA 4312, Université de Rouen, Evreux, France
| | - German Bou
- Servicio de Microbiología-INIBIC, Complejo Hospitalario Universitario A Coruña (CHUAC), Spain
| | - Isabelle Shalk
- UMR 7242, Université de Strasbourg-CNRS, ESBS, Illkirch, France
| | - Thierry Jouenne
- CNRS UMR 6270 & FR3038, Normandie Univ, Laboratoire Polymères, Biopolymères & Surfaces, Université de Rouen, Mont Saint Aignan, France
| | - Xavier Vila-Farrés
- Center for International Health Research, CRESIB, Hospital Clínic, University of Barcelona, Spain
| | - Emmanuelle Dé
- CNRS UMR 6270 & FR3038, Normandie Univ, Laboratoire Polymères, Biopolymères & Surfaces, Université de Rouen, Mont Saint Aignan, France
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Characterization of an Acinetobacter baumannii lptD Deletion Strain: Permeability Defects and Response to Inhibition of Lipopolysaccharide and Fatty Acid Biosynthesis. J Bacteriol 2015; 198:731-41. [PMID: 26668262 DOI: 10.1128/jb.00639-15] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2015] [Accepted: 12/04/2015] [Indexed: 01/03/2023] Open
Abstract
UNLABELLED Lipid A on the Gram-negative outer membrane (OM) is synthesized in the cytoplasm by the Lpx pathway and translocated to the OM by the Lpt pathway. Some Acinetobacter baumannii strains can tolerate the complete loss of lipopolysaccharide (LPS) resulting from the inactivation of early LPS pathway genes such as lpxC. Here, we characterized a mutant deleted for lptD, which encodes an OM protein that mediates the final translocation of fully synthesized LPS to the OM. Cells lacking lptD had a growth defect comparable to that of an lpxC deletion mutant under the growth conditions tested but were more sensitive to hydrophobic antibiotics, revealing a more significant impact on cell permeability from impaired LPS translocation than from the loss of LPS synthesis. Consistent with this, ATP leakage and N-phenyl-1-naphthylamine (NPN) fluorescence assays indicated a more severe impact of lptD deletion than of lpxC deletion on inner and outer membrane permeability, respectively. Targeted liquid chromatography-mass spectrometry (LCMS) analysis of LPS intermediates from UDP-3-O-R-3-hydroxylauroyl-N-acetyl-α-d-glucosamine through lipid IV(A) showed that the loss of LptD caused an accumulation of lipid IV(A). This suggested that pathway intermediate accumulation or mislocalization caused by the blockage of later LPS pathway steps impacts envelope integrity. Supporting this notion, chemical inhibition of lipid A precursor enzymes, including LpxC and FabB/F, in the lptD deletion strain partially rescued growth and permeability defects. IMPORTANCE New antibiotics to treat Gram-negative bacterial infections are urgently needed. Inhibition of LPS biosynthesis is attractive because this would impact viability and cell permeability. Therefore, a better understanding of this pathway is important, especially in strains such as A. baumannii ATCC 19606, where LPS biosynthesis is not essential in vitro. We show that ATCC 19606 also survives the loss of the final translocation of LPS into the OM (lptD deletion). Intriguingly, this impaired cell envelope integrity more than the loss of LPS biosynthesis (lpxC deletion), presumably due to the accumulation of toxic intermediates. Supporting this, chemical inhibition of LPS biosynthesis partially reversed this permeability defect. This extends our understanding of the LPS machinery and provides insights into potential interrelationships of the target steps along this important pathway.
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Acinetobacter baumannii Genes Required for Bacterial Survival during Bloodstream Infection. mSphere 2015; 1:mSphere00013-15. [PMID: 27303682 PMCID: PMC4863628 DOI: 10.1128/msphere.00013-15] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2015] [Accepted: 09/28/2015] [Indexed: 11/25/2022] Open
Abstract
A. baumannii is a significant cause of bacterial bloodstream infection in humans. Since multiple antibiotic resistance is becoming more common among strains of A. baumannii, there is an urgent need to develop novel tools to treat infections caused by this dangerous pathogen. To develop knowledge-guided treatment approaches for A. baumannii, a thorough understanding of the mechanism by which this pathogen causes bloodstream infection is required. Here, using a mouse model of infection, we report the identification of A. baumannii genes that are critical for the ability of this pathogen to cause bloodstream infections. This study lays the foundation for future research on A. baumannii genes that can be targeted to develop novel therapeutics against this emerging human pathogen. Acinetobacter baumannii is emerging as a leading global multiple-antibiotic-resistant nosocomial pathogen. The identity of genes essential for pathogenesis in a mammalian host remains largely unknown. Using transposon-directed insertion-site sequencing (TraDIS), we identified A. baumannii genes involved in bacterial survival in a leukopenic mouse model of bloodstream infection. Mice were inoculated with a pooled transposon mutant library derived from 109,000 mutants, and TraDIS was used to map transposon insertion sites in the genomes of bacteria in the inoculum and of bacteria recovered from mouse spleens. Unique transposon insertion sites were mapped and used to calculate a fitness factor for every insertion site based on its relative abundance in the inoculum and postinfection libraries. Eighty-nine transposon insertion mutants that were underrepresented after experimental infection in mice compared to their presence in the inocula were delineated as candidates for further evaluation. Genetically defined mutants lacking feoB (ferrous iron import), ddc (d-ala-d-ala-carboxypeptidase), and pntB (pyridine nucleotide transhydrogenase subunit) exhibited a fitness defect during systemic infection resulting from bacteremia. In vitro, these mutants, as well as a fepA (ferric enterobactin receptor) mutant, are defective in survival in human serum and within macrophages and are hypersensitive to killing by antimicrobial peptides compared to the survival of the parental strain under these conditions. Our data demonstrate that FepA is involved in the uptake of exogenous enterobactin in A. baumannii. Genetic complementation rescues the phenotypes of mutants in assays that emulate conditions encountered during infection. In summary, we have determined novel A. baumannii fitness genes involved in the pathogenesis of mammalian infection. IMPORTANCEA. baumannii is a significant cause of bacterial bloodstream infection in humans. Since multiple antibiotic resistance is becoming more common among strains of A. baumannii, there is an urgent need to develop novel tools to treat infections caused by this dangerous pathogen. To develop knowledge-guided treatment approaches for A. baumannii, a thorough understanding of the mechanism by which this pathogen causes bloodstream infection is required. Here, using a mouse model of infection, we report the identification of A. baumannii genes that are critical for the ability of this pathogen to cause bloodstream infections. This study lays the foundation for future research on A. baumannii genes that can be targeted to develop novel therapeutics against this emerging human pathogen.
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Hammerstrom TG, Beabout K, Clements TP, Saxer G, Shamoo Y. Acinetobacter baumannii Repeatedly Evolves a Hypermutator Phenotype in Response to Tigecycline That Effectively Surveys Evolutionary Trajectories to Resistance. PLoS One 2015; 10:e0140489. [PMID: 26488727 PMCID: PMC4619398 DOI: 10.1371/journal.pone.0140489] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2015] [Accepted: 09/25/2015] [Indexed: 01/23/2023] Open
Abstract
The evolution of hypermutators in response to antibiotic treatment in both clinical and laboratory settings provides a unique context for the study of adaptive evolution. With increased mutation rates, the number of hitchhiker mutations within an evolving hypermutator population is remarkably high and presents substantial challenges in determining which mutations are adaptive. Intriguingly however, hypermutators also provide an opportunity to explore deeply the accessible evolutionary trajectories that lead to increased organism fitness, in this case the evolution of antibiotic resistance to the clinically relevant antibiotic tigecycline by the hospital pathogen Acinetobacter baumannii. Using a continuous culture system, AB210M, a clinically derived strain of A. baumannii, was evolved to tigecycline resistance. Analysis of the adapted populations showed that nearly all the successful lineages became hypermutators via movement of a mobile element to inactivate mutS. In addition, metagenomic analysis of population samples revealed another 896 mutations that occurred at a frequency greater than 5% in the population, while 38 phenotypically distinct individual colonies harbored a total of 1712 mutations. These mutations were scattered throughout the genome and affected ~40% of the coding sequences. The most highly mutated gene was adeS, a known tigecycline-resistance gene; however, adeS was not solely responsible for the high level of TGC resistance. Sixteen other genes stood out as potentially relevant to increased resistance. The five most prominent candidate genes (adeS, rpsJ, rrf, msbA, and gna) consistently re-emerged in subsequent replicate population studies suggesting they are likely to play a role in adaptation to tigecycline. Interestingly, the repeated evolution of a hypermutator phenotype in response to antibiotic stress illustrates not only a highly adaptive strategy to resistance, but also a remarkably efficient survey of successful evolutionary trajectories.
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Affiliation(s)
- Troy G Hammerstrom
- Department of Biosciences, Rice University, Houston, Texas, United States of America
| | - Kathryn Beabout
- Department of Biosciences, Rice University, Houston, Texas, United States of America
| | - Thomas P Clements
- Department of Biosciences, Rice University, Houston, Texas, United States of America
| | - Gerda Saxer
- Department of Biosciences, Rice University, Houston, Texas, United States of America
| | - Yousif Shamoo
- Department of Biosciences, Rice University, Houston, Texas, United States of America
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Lin MF, Tsai PW, Chen JY, Lin YY, Lan CY. OmpA Binding Mediates the Effect of Antimicrobial Peptide LL-37 on Acinetobacter baumannii. PLoS One 2015; 10:e0141107. [PMID: 26484669 PMCID: PMC4618850 DOI: 10.1371/journal.pone.0141107] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2015] [Accepted: 10/05/2015] [Indexed: 02/06/2023] Open
Abstract
Multidrug-resistant Acinetobacter baumannii has recently emerged as an important pathogen in nosocomial infection; thus, effective antimicrobial regimens are urgently needed. Human antimicrobial peptides (AMPs) exhibit multiple functions and antimicrobial activities against bacteria and fungi and are proposed to be potential adjuvant therapeutic agents. This study examined the effect of the human cathelicidin-derived AMP LL-37 on A. baumannii and revealed the underlying mode of action. We found that LL-37 killed A. baumannii efficiently and reduced cell motility and adhesion. The bacteria-killing effect of LL-37 on A. baumannii was more efficient compared to other AMPs, including human ß–defensin 3 (hBD3) and histatin 5 (Hst5). Both flow cytometric analysis and immunofluorescence staining showed that LL-37 bound to A. baumannii cells. Moreover, far-western analysis demonstrated that LL-37 could bind to the A. baumannii OmpA (AbOmpA) protein. An ELISA assay indicated that biotin-labelled LL-37 (BA-LL37) bound to the AbOmpA74-84 peptide in a dose-dependent manner. Using BA-LL37 as a probe, the ~38 kDa OmpA signal was detected in the wild type but the ompA deletion strain did not show the protein, thereby validating the interaction. Finally, we found that the ompA deletion mutant was more sensitive to LL-37 and decreased cell adhesion by 32% compared to the wild type. However, ompA deletion mutant showed a greatly reduced adhesion defect after LL-37 treatment compared to the wild strain. Taken together, this study provides evidence that LL-37 affects A. baumannii through OmpA binding.
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Affiliation(s)
- Ming-Feng Lin
- Department of Medicine, National Taiwan University Hospital Chu-Tung Branch, Hsin-Chu County, Taiwan
| | - Pei-Wen Tsai
- Institute of Molecular and Cellular Biology, National Tsing Hua University, Hsin-Chu City, Taiwan
| | - Jeng-Yi Chen
- Institute of Molecular and Cellular Biology, National Tsing Hua University, Hsin-Chu City, Taiwan
| | - Yun-You Lin
- Institute of Molecular and Cellular Biology, National Tsing Hua University, Hsin-Chu City, Taiwan
| | - Chung-Yu Lan
- Institute of Molecular and Cellular Biology, National Tsing Hua University, Hsin-Chu City, Taiwan
- Department of Life Science, National Tsing Hua University, Hsin-Chu City, Taiwan
- * E-mail:
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