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Jiao Y, Yan J, Sutaria DS, Lu P, Vicchiarelli M, Reyna Z, Ruiz-Delgado J, Burk E, Moon E, Shah NR, Spellberg B, Bonomo RA, Drusano GL, Louie A, Luna BM, Bulitta JB. Population pharmacokinetics and humanized dosage regimens matching the peak, area, trough, and range of amikacin plasma concentrations in immune-competent murine bloodstream and lung infection models. Antimicrob Agents Chemother 2024; 68:e0139423. [PMID: 38289076 PMCID: PMC10916399 DOI: 10.1128/aac.01394-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2023] [Accepted: 12/22/2023] [Indexed: 03/07/2024] Open
Abstract
Amikacin is an FDA-approved aminoglycoside antibiotic that is commonly used. However, validated dosage regimens that achieve clinically relevant exposure profiles in mice are lacking. We aimed to design and validate humanized dosage regimens for amikacin in immune-competent murine bloodstream and lung infection models of Acinetobacter baumannii. Plasma and lung epithelial lining fluid (ELF) concentrations after single subcutaneous doses of 1.37, 13.7, and 137 mg/kg of body weight were simultaneously modeled via population pharmacokinetics. Then, humanized amikacin dosage regimens in mice were designed and prospectively validated to match the peak, area, trough, and range of plasma concentration profiles in critically ill patients (clinical dose: 25-30 mg/kg of body weight). The pharmacokinetics of amikacin were linear, with a clearance of 9.93 mL/h in both infection models after a single dose. However, the volume of distribution differed between models, resulting in an elimination half-life of 48 min for the bloodstream and 36 min for the lung model. The drug exposure in ELF was 72.7% compared to that in plasma. After multiple q6h dosing, clearance decreased by ~80% from the first (7.35 mL/h) to the last two dosing intervals (~1.50 mL/h) in the bloodstream model. Likewise, clearance decreased by 41% from 7.44 to 4.39 mL/h in the lung model. The humanized dosage regimens were 117 mg/kg of body weight/day in mice [administered in four fractions 6 h apart (q6h): 61.9%, 18.6%, 11.3%, and 8.21% of total dose] for the bloodstream and 96.7 mg/kg of body weight/day (given q6h as 65.1%, 16.9%, 10.5%, and 7.41%) for the lung model. These validated humanized dosage regimens and population pharmacokinetic models support translational studies with clinically relevant amikacin exposure profiles.
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Affiliation(s)
- Yuanyuan Jiao
- Department of Pharmacotherapy and Translational Research, College of Pharmacy, University of Florida, Orlando, Florida, USA
| | - Jun Yan
- Department of Molecular Microbiology and Immunology, Keck School of Medicine, University of Southern California, Los Angeles, California, USA
| | - Dhruvitkumar S. Sutaria
- Department of Pharmacotherapy and Translational Research, College of Pharmacy, University of Florida, Orlando, Florida, USA
| | - Peggy Lu
- Department of Molecular Microbiology and Immunology, Keck School of Medicine, University of Southern California, Los Angeles, California, USA
| | - Michael Vicchiarelli
- Institute for Therapeutic Innovation, College of Medicine, University of Florida, Orlando, Florida, USA
| | - Zeferino Reyna
- Department of Molecular Microbiology and Immunology, Keck School of Medicine, University of Southern California, Los Angeles, California, USA
| | - Juan Ruiz-Delgado
- Department of Molecular Microbiology and Immunology, Keck School of Medicine, University of Southern California, Los Angeles, California, USA
| | - Elizabeth Burk
- Department of Molecular Microbiology and Immunology, Keck School of Medicine, University of Southern California, Los Angeles, California, USA
| | - Eugene Moon
- Department of Molecular Microbiology and Immunology, Keck School of Medicine, University of Southern California, Los Angeles, California, USA
| | - Nirav R. Shah
- Department of Pharmacotherapy and Translational Research, College of Pharmacy, University of Florida, Orlando, Florida, USA
| | - Brad Spellberg
- Los Angeles County-USC (LAC+USC) Medical Center, Los Angeles, California, USA
| | - Robert A. Bonomo
- Department of Medicine, Case Western Reserve University, Cleveland, Ohio, USA
- Department of Molecular Biology and Microbiology, Case Western Reserve University, Cleveland, Ohio, USA
- Department of Biochemistry, Case Western Reserve University, Cleveland, Ohio, USA
- Department of Pharmacology, Case Western Reserve University, Cleveland, Ohio, USA
- Department of Proteomics and Bioinformatics, Case Western Reserve University, Cleveland, Ohio, USA
- Louis Stokes Cleveland Department of Veterans Affairs, Cleveland, Ohio, USA
- Case VA Center for Antimicrobial Resistance and Epidemiology (Case VA CARES), Cleveland, Ohio, USA
| | - George L. Drusano
- Institute for Therapeutic Innovation, College of Medicine, University of Florida, Orlando, Florida, USA
| | - Arnold Louie
- Institute for Therapeutic Innovation, College of Medicine, University of Florida, Orlando, Florida, USA
| | - Brian M. Luna
- Department of Molecular Microbiology and Immunology, Keck School of Medicine, University of Southern California, Los Angeles, California, USA
| | - Jürgen B. Bulitta
- Department of Pharmacotherapy and Translational Research, College of Pharmacy, University of Florida, Orlando, Florida, USA
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2
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Nielsen TB, Yan J, Slarve M, Li R, Junge JA, Luna BM, Wilkinson I, Yerramalla U, Spellberg B. Development of a Bispecific Antibody Targeting Clinical Isolates of Acinetobacter baumannii. J Infect Dis 2023; 227:1042-1049. [PMID: 36617220 PMCID: PMC10319980 DOI: 10.1093/infdis/jiac499] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2022] [Revised: 12/16/2022] [Accepted: 01/05/2023] [Indexed: 01/09/2023] Open
Abstract
BACKGROUND We previously reported developing 2 anticapsular monoclonal antibodies (mAbs) as a novel therapy for Acinetobacter baumannii infections. We sought to determine whether a bispecific mAb (bsAb) could improve avidity and efficacy while maximizing strain coverage in one molecule. METHODS Humanized mAb 65 was cloned into a single-chain variable fragment and attached to humanized mAb C8, combining their paratopes into a single bsAb (C73). We tested bsAb C73's strain coverage, binding affinity, ex vivo opsonic activity, and in vivo efficacy compared to each mAb alone and combined. RESULTS The bsAb demonstrated strain coverage, binding affinity, opsonization, and in vivo efficacy superior to either original mAb alone or combined. CONCLUSIONS A humanized bsAb targeting distinct A. baumannii capsule moieties enabled potent and effective coverage of disparate A. baumannii clinical isolates. The bsAb enhances feasibility of development by minimizing the number of components of a promising novel therapeutic for these difficult-to-treat infections.
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Affiliation(s)
- Travis B Nielsen
- Stritch School of Medicine, Loyola University Chicago, Maywood, Illinois, USA
- Parkinson School of Health Sciences and Public Health, Loyola University Chicago, Maywood, Illinois, USA
- Department of Molecular Microbiology and Immunology, Keck School of Medicine of the University of Southern California, Los Angeles, California, USA
| | - Jun Yan
- Department of Molecular Microbiology and Immunology, Keck School of Medicine of the University of Southern California, Los Angeles, California, USA
| | - Matthew Slarve
- Department of Molecular Microbiology and Immunology, Keck School of Medicine of the University of Southern California, Los Angeles, California, USA
| | - Rachel Li
- Department of Molecular Microbiology and Immunology, Keck School of Medicine of the University of Southern California, Los Angeles, California, USA
| | - Jason A Junge
- Translational Imaging Center, School of Engineering, University of Southern California, Los Angeles, California, USA
| | - Brian M Luna
- Department of Molecular Microbiology and Immunology, Keck School of Medicine of the University of Southern California, Los Angeles, California, USA
| | | | | | - Brad Spellberg
- Los Angeles County + University of Southern California Medical Center, Los Angeles, California, USA
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3
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Slarve M, Reyna Z, Burk E, Ruiz-Delgado J, Li R, Yan J, Luna B, Spellberg B. Therapeutic, Humanized Monoclonal Antibody Exhibits Broad Binding and Protective Efficacy against Acinetobacter baumannii. Antimicrob Agents Chemother 2023; 67:e0008623. [PMID: 36853012 PMCID: PMC10019318 DOI: 10.1128/aac.00086-23] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2023] [Accepted: 02/08/2023] [Indexed: 03/01/2023] Open
Abstract
Acinetobacter baumannii is an extremely drug-resistant pathogen necessitating the development of new therapies. We seek to generate a cocktail of monoclonal antibodies (MAbs) that can target the full diversity of A. baumannii isolates. We have newly identified the antibody MAb5. Here, we demonstrate that MAb5 has broad binding against U.S. (n = 300) and international (n = 250) isolates (72.24% and 28.76%, respectively), likely targets O-antigen capsular carbohydrates, and exhibits protective efficacy in vivo.
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Affiliation(s)
- Matthew Slarve
- Department of Molecular Microbiology and Immunology, Keck School of Medicine of USC, Los Angeles, California, USA
| | - Zeferino Reyna
- Department of Molecular Microbiology and Immunology, Keck School of Medicine of USC, Los Angeles, California, USA
| | - Elizabeth Burk
- Department of Molecular Microbiology and Immunology, Keck School of Medicine of USC, Los Angeles, California, USA
| | - Juan Ruiz-Delgado
- Department of Molecular Microbiology and Immunology, Keck School of Medicine of USC, Los Angeles, California, USA
| | - Rachel Li
- Department of Molecular Microbiology and Immunology, Keck School of Medicine of USC, Los Angeles, California, USA
| | - Jun Yan
- Department of Molecular Microbiology and Immunology, Keck School of Medicine of USC, Los Angeles, California, USA
| | - Brian Luna
- Department of Molecular Microbiology and Immunology, Keck School of Medicine of USC, Los Angeles, California, USA
| | - Brad Spellberg
- Los Angeles County-USC (LAC+USC) Medical Center, Los Angeles, California, USA
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4
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Shadan A, Pathak A, Ma Y, Pathania R, Singh RP. Deciphering the virulence factors, regulation, and immune response to Acinetobacter baumannii infection. Front Cell Infect Microbiol 2023; 13:1053968. [PMID: 36968113 PMCID: PMC10038080 DOI: 10.3389/fcimb.2023.1053968] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2022] [Accepted: 02/06/2023] [Indexed: 02/25/2023] Open
Abstract
Deciphering the virulence factors, regulation, and immune response to Acinetobacter baumannii infectionAcinetobacter baumannii is a gram-negative multidrug-resistant nosocomial pathogen and a major cause of hospital acquired infetions. Carbapenem resistant A. baumannii has been categorised as a Priority1 critial pathogen by the World Health Organisation. A. baumannii is responsible for infections in hospital settings, clinical sectors, ventilator-associated pneumonia, and bloodstream infections with a mortality rates up to 35%. With the development of advanced genome sequencing, molecular mechanisms of manipulating bacterial genomes, and animal infection studies, it has become more convenient to identify the factors that play a major role in A. baumannii infection and its persistence. In the present review, we have explored the mechanism of infection, virulence factors, and various other factors associated with the pathogenesis of this organism. Additionally, the role of the innate and adaptive immune response, and the current progress in the development of innovative strategies to combat this multidrug-resistant pathogen is also discussed.
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Affiliation(s)
- Afreen Shadan
- Department of Microbiology, Dr. Shyama Prasad Mukherjee University, Ranchi, Jharkhand, India
| | - Avik Pathak
- Department of Biosciences and Bioengineering, Indian Institute of Technology, Roorkee, India
| | - Ying Ma
- College of Resources and Environment, Southwest University, Chongqing, China
- *Correspondence: Ying Ma, ; Ranjana Pathania, ; Rajnish Prakash Singh,
| | - Ranjana Pathania
- Department of Biosciences and Bioengineering, Indian Institute of Technology, Roorkee, India
- *Correspondence: Ying Ma, ; Ranjana Pathania, ; Rajnish Prakash Singh,
| | - Rajnish Prakash Singh
- Department of Bioengineering and Biotechnology, Birla Institute of Technology, Ranchi, Jharkhand, India
- *Correspondence: Ying Ma, ; Ranjana Pathania, ; Rajnish Prakash Singh,
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5
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Trebosc V, Lucchini V, Narwal M, Wicki B, Gartenmann S, Schellhorn B, Schill J, Bourotte M, Frey D, Grünberg J, Trauner A, Ferrari L, Felici A, Champion OL, Gitzinger M, Lociuro S, Kammerer RA, Kemmer C, Pieren M. Targeting virulence regulation to disarm Acinetobacter baumannii pathogenesis. Virulence 2022; 13:1868-1883. [PMID: 36261919 PMCID: PMC9586577 DOI: 10.1080/21505594.2022.2135273] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The development of anti-virulence drug therapy against Acinetobacter baumannii infections would provide an alternative to traditional antibacterial therapy that are increasingly failing. Here, we demonstrate that the OmpR transcriptional regulator plays a pivotal role in the pathogenesis of diverse A. baumannii clinical strains in multiple murine and G. mellonella invertebrate infection models. We identified OmpR-regulated genes using RNA sequencing and further validated two genes whose expression can be used as robust biomarker to quantify OmpR inhibition in A. baumannii. Moreover, the determination of the structure of the OmpR DNA binding domain of A. baumannii and the development of in vitro protein-DNA binding assays enabled the identification of an OmpR small molecule inhibitor. We conclude that OmpR is a valid and unexplored target to fight A. baumannii infections and we believe that the described platform combining in silico methods, in vitro OmpR inhibitory assays and in vivo G. mellonella surrogate infection model will facilitate future drug discovery programs.
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Affiliation(s)
| | - Valentina Lucchini
- BioVersys AG, Basel, Switzerland.,Biozentrum, University of Basel, Basel, Switzerland
| | | | | | | | | | | | | | - Daniel Frey
- Laboratory of Biomolecular Research, Division of Biology and Chemistry, Paul Scherrer Institute, Villigen, Switzerland
| | - Jürgen Grünberg
- Center for Radiopharmaceutical Sciences ETH-PSI-USZ, Paul Scherrer Institute, Villigen, Switzerland
| | | | - Livia Ferrari
- Microbiology Discovery, Aptuit Srl, an Evotec Company, Verona, Italy
| | - Antonio Felici
- Microbiology Discovery, Aptuit Srl, an Evotec Company, Verona, Italy
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6
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Jeffreys S, Chambers JP, Yu JJ, Hung CY, Forsthuber T, Arulanandam BP. Insights into Acinetobacter baumannii protective immunity. Front Immunol 2022; 13:1070424. [PMID: 36466845 PMCID: PMC9716351 DOI: 10.3389/fimmu.2022.1070424] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2022] [Accepted: 11/07/2022] [Indexed: 11/19/2022] Open
Abstract
Acinetobacter baumannii is a nosocomic opportunistic Gram-negative bacteria known for its extensive drug-resistant phenotype. A. baumannii hospital-acquired infections are major contributors to increased costs and mortality observed during the COVID-19 pandemic. With few effective antimicrobials available for treatment of this pathogen, immune-based therapy becomes an attractive strategy to combat multi-drug resistant Acinetobacter infection. Immunotherapeutics is a field of growing interest with advances in vaccines and monoclonal antibodies providing insight into the protective immune response required to successfully combat this pathogen. This review focuses on current knowledge describing the adaptive immune response to A. baumannii, the importance of antibody-mediated protection, developments in cell-mediated protection, and their respective therapeutic application going forward. With A. baumannii’s increasing resistance to most current antimicrobials, elucidating an effective host adaptive immune response is paramount in the guidance of future immunotherapeutic development.
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Affiliation(s)
- Sean Jeffreys
- Department of Molecular Microbiology and Immunology, University of Texas at San Antonio, San Antonio, TX, United States
| | - James P. Chambers
- Department of Molecular Microbiology and Immunology, University of Texas at San Antonio, San Antonio, TX, United States
| | - Jieh-Juen Yu
- Department of Molecular Microbiology and Immunology, University of Texas at San Antonio, San Antonio, TX, United States
| | - Chiung-Yu Hung
- Department of Molecular Microbiology and Immunology, University of Texas at San Antonio, San Antonio, TX, United States
| | - Thomas Forsthuber
- Department of Molecular Microbiology and Immunology, University of Texas at San Antonio, San Antonio, TX, United States
| | - Bernard P. Arulanandam
- Department of Molecular Microbiology and Immunology, University of Texas at San Antonio, San Antonio, TX, United States
- Department of Immunology, Tufts University School of Medicine, Boston, MA, United States
- *Correspondence: Bernard P. Arulanandam,
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7
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Li FJ, Starrs L, Mathur A, Ishii H, Man SM, Burgio G. Differential activation of NLRP3 inflammasome by Acinetobacter baumannii strains. PLoS One 2022; 17:e0277019. [PMID: 36318583 PMCID: PMC9624416 DOI: 10.1371/journal.pone.0277019] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2022] [Accepted: 10/17/2022] [Indexed: 11/07/2022] Open
Abstract
Acinetobacter baumannii is an emerging nosocomial, opportunistic pathogen with growing clinical significance globally. A. baumannii has an exceptional ability to rapidly develop drug resistance. It is frequently responsible for ventilator-associated pneumonia in clinical settings and inflammation resulting in severe sepsis. The inflammatory response is mediated by host pattern-recognition receptors and the inflammasomes. Inflammasome activation triggers inflammatory responses, including the secretion of the pro-inflammatory cytokines IL-1β and IL-18, the recruitment of innate immune effectors against A. baumannii infection, and the induction programmed cell death by pyroptosis. An important knowledge gap is how variation among clinical isolates affects the host’s innate response and activation of the inflammasome during A. baumannii infection. In this study, we compared nine A. baumannii strains, including clinical locally-acquired isolates, in their ability to induce activation of the inflammasome and programmed cell death in primary macrophages, epithelial lung cell line and mice. We found a variation in survival outcomes of mice and bacterial dissemination in organs among three commercially available A. baumannii strains, likely due to the differences in virulence between strains. Interestingly, we found variability among A. baumannii strains in activation of the NLRP3 inflammasome, non-canonical Caspase-11 pathway, plasmatic secretion of the pro-inflammatory cytokine IL-1β and programmed cell death. Our study highlights the importance of utilising multiple bacterial strains and clinical isolates with different virulence to investigate the innate immune response to A. baumannii infection.
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Affiliation(s)
- Fei-Ju Li
- Division of Immunology and Infectious Disease, The John Curtin School of Medical Research, The Australian National University, Canberra, ACT, Australia
| | - Lora Starrs
- Division of Immunology and Infectious Disease, The John Curtin School of Medical Research, The Australian National University, Canberra, ACT, Australia
| | - Anukriti Mathur
- Division of Immunology and Infectious Disease, The John Curtin School of Medical Research, The Australian National University, Canberra, ACT, Australia
| | - Hikari Ishii
- Division of Immunology and Infectious Disease, The John Curtin School of Medical Research, The Australian National University, Canberra, ACT, Australia
| | - Si Ming Man
- Division of Immunology and Infectious Disease, The John Curtin School of Medical Research, The Australian National University, Canberra, ACT, Australia
| | - Gaetan Burgio
- Division of Immunology and Infectious Disease, The John Curtin School of Medical Research, The Australian National University, Canberra, ACT, Australia
- * E-mail:
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8
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Liu Z, Xu W. Neutrophil and Macrophage Response in Acinetobacter Baumannii Infection and Their Relationship to Lung Injury. Front Cell Infect Microbiol 2022; 12:890511. [PMID: 35873147 PMCID: PMC9298752 DOI: 10.3389/fcimb.2022.890511] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2022] [Accepted: 06/08/2022] [Indexed: 11/25/2022] Open
Abstract
Acinetobacter baumannii (AB) infection has become a threat to global public health. AB is one of the main pathogens causing nosocomial infections, especially ventilator-associated pneumonia. AB easily develops resistance against a variety of antibiotics, which makes the treatment of AB infections difficult. Therefore, it is necessary to study new treatment plans like anti-infection immunity. Both animal models of AB infection and in vitro cell experiments show that macrophages are activated in the early stage of the immune response and regulate the recruitment of neutrophils, thus playing a role in clearing AB. AB components and the immune responses they induce can lead to injury of the infected organ, mostly in the lungs. Understanding the response of innate immunity to ABs at different stages after infection and the relationship between the response and lung injury can help to develop new immunotherapy methods and prevent lung injury. This article provides a comprehensive review of the response of neutrophils and macrophages to AB infection and their association with lung injury to develop effective therapies for AB infection and prevent lung injury.
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Affiliation(s)
- Zhaojun Liu
- Department of Pediatrics, Shengjing Hospital of China Medical University, Shenyang, China
| | - Wei Xu
- Department of Pediatrics, Shengjing Hospital of China Medical University, Shenyang, China
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9
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Tiku V, Kew C, Kofoed EM, Peng Y, Dikic I, Tan MW. Acinetobacter baumannii Secretes a Bioactive Lipid That Triggers Inflammatory Signaling and Cell Death. Front Microbiol 2022; 13:870101. [PMID: 35615509 PMCID: PMC9125205 DOI: 10.3389/fmicb.2022.870101] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2022] [Accepted: 03/28/2022] [Indexed: 11/13/2022] Open
Abstract
Acinetobacter baumannii is a highly pathogenic Gram-negative bacterium that causes severe infections with very high fatality rates. A. baumannii infection triggers innate as well as adaptive immunity, however, our understanding of the inflammatory factors secreted by A. baumannii that alarm the immune system remains limited. In this study, we report that the lab adapted and clinical strains of A. baumannii secrete an inflammatory bioactive factor which activates TLR2, leading to canonical IRAK4-dependent NF-κB signaling and production of pro-inflammatory cytokines interleukin (IL)-6 and IL-8 and activation of the inflammasome pathway causing pyroptotic cell death. Biochemical fractionation of the A. baumannii culture filtrate revealed the hydrophobic nature of the inflammatory factor. Concordantly, lipase treatment of the culture filtrate or TLR2 inhibition in macrophages abrogated NF-κB activation and cell death induction. Culture filtrates from the LPS- and lipoprotein-deficient A. baumannii mutants retain immuno-stimulatory properties suggesting that a lipid other than these known stimulatory molecules can trigger inflammation during A. baumannii infection. Our results reveal that A. baumannii secretes a previously unappreciated inflammatory bioactive lipid that activates multiple pro-inflammatory signaling pathways and induces cell death in human and murine macrophages.
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Affiliation(s)
- Varnesh Tiku
- Department of Infectious Diseases, Genentech, South San Francisco, CA, United States
- *Correspondence: Varnesh Tiku,
| | - Chun Kew
- Faculty of Medicine, Institute of Biochemistry II, Goethe University Frankfurt, Frankfurt, Germany
- Buchmann Institute for Molecular Life Sciences, Goethe University Frankfurt, Frankfurt, Germany
| | - Eric M. Kofoed
- Department of Infectious Diseases, Genentech, South San Francisco, CA, United States
| | - Yutian Peng
- Department of Infectious Diseases, Genentech, South San Francisco, CA, United States
| | - Ivan Dikic
- Faculty of Medicine, Institute of Biochemistry II, Goethe University Frankfurt, Frankfurt, Germany
- Buchmann Institute for Molecular Life Sciences, Goethe University Frankfurt, Frankfurt, Germany
- Max Planck Institute of Biophysics, Frankfurt, Germany
- Ivan Dikic,
| | - Man-Wah Tan
- Department of Infectious Diseases, Genentech, South San Francisco, CA, United States
- Man-Wah Tan,
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10
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Abstract
The spread of antibiotic-resistant Acinetobacter baumannii poses a significant threat to public health worldwide. This nosocomial bacterial pathogen can be associated with life-threatening infections, particularly in intensive care units. A. baumannii is mainly described as an extracellular pathogen with restricted survival within cells. This study shows that a subset of A. baumannii clinical isolates extensively multiply within nonphagocytic immortalized and primary cells without the induction of apoptosis and with bacterial clusters visible up to 48 h after infection. This phenotype was observed for the A. baumannii C4 strain associated with high mortality in a hospital outbreak and the A. baumannii ABC141 strain, which was isolated from the skin but was found to be hyperinvasive. Intracellular multiplication of these A. baumannii strains occurred within spacious single membrane-bound vacuoles, labeled with the lysosomal associate membrane protein (LAMP1). However, these compartments excluded lysotracker, an indicator of acidic pH, suggesting that A. baumannii can divert its trafficking away from the lysosomal degradative pathway. These compartments were also devoid of autophagy features. A high-content microscopy screen of 43 additional A. baumannii clinical isolates highlighted various phenotypes, and (i) the majority of isolates remained extracellular, (ii) a significant proportion was capable of invasion and limited persistence, and (iii) three more isolates efficiently multiplied within LAMP1-positive vacuoles, one of which was also hyperinvasive. These data identify an intracellular niche for specific A. baumannii clinical isolates that enables extensive multiplication in an environment protected from host immune responses and out of reach of many antibiotics. IMPORTANCE Multidrug-resistant Acinetobacter baumannii isolates are associated with significant morbidity and mortality in hospitals worldwide. Understanding their pathogenicity is critical for improving therapeutic management. Although A. baumannii can steadily adhere to surfaces and host cells, most bacteria remain extracellular. Recent studies have shown that a small proportion of bacteria can invade cells but present limited survival. We have found that some A. baumannii clinical isolates can establish a specialized intracellular niche that sustains extensive intracellular multiplication for a prolonged time without induction of cell death. We propose that this intracellular compartment allows A. baumannii to escape the cell’s normal degradative pathway, protecting bacteria from host immune responses and potentially hindering antibiotic accessibility. This may contribute to A. baumannii persistence, relapsing infections, and enhanced mortality in susceptible patients. A high-content microscopy-based screen confirmed that this pathogenicity trait is present in other clinical A. baumannii isolates. There is an urgent need for new antibiotics or alternative antimicrobial approaches, particularly to combat carbapenem-resistant A. baumannii. The discovery of an intracellular niche for this pathogen, as well as hyperinvasive isolates, may help guide the development of antimicrobial therapies and diagnostics in the future.
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11
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Staphylococcus aureus and Acinetobacter sp. inhibit osseointegration of orthopaedic implants. Infect Immun 2022; 90:e0066921. [PMID: 35099267 DOI: 10.1128/iai.00669-21] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Bacterial infections routinely cause inflammation and thereby impair osseointegration of orthopaedic implants. Acinetobacter spp., which causes osteomyelitis following trauma, on or off the battlefield, was however reported to cause neither osteomyelitis nor osteolysis in rodents. We therefore compared the effects of Acinetobacter strain M2 to those of Staphylococcus aureus in a murine implant infection model. Sterile implants and implants with adherent bacteria were inserted in the femur of mice. Bacterial burden, levels of pro-inflammatory cytokines, and osseointegration were measured. All infections were localized to the implant site. Infection with either S. aureus or Acinetobacter strain M2 increased the levels of pro-inflammatory cytokines and the chemokine CCL2 in the surrounding femurs, inhibited bone formation around the implant, and caused loss of the surrounding cortical bone leading to decreases in both histomorphometric and biomechanical measures of osseointegration. Genetic deletion of TLR2 and TLR4 from the mice partially reduced the effects of Acinetobacter strain M2 on osseointegration but did not alter the effects of S. aureus. This is the first report that Acinetobacter spp. impair osseointegration of orthopaedic implants in mice and the murine model developed for this study will be useful for future efforts to clarify the mechanism of implant failure due to Acinetobacter spp. and to assess novel diagnostic tools or therapeutic agents.
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Kamuyu G, Ercoli G, Ramos-Sevillano E, Willcocks S, Kewcharoenwong C, Kiratisin P, Taylor PW, Wren BW, Lertmemongkolchai G, Stabler RA, Brown JS. Strain Specific Variations in Acinetobacter baumannii Complement Sensitivity. Front Immunol 2022; 13:853690. [PMID: 35812377 PMCID: PMC9258041 DOI: 10.3389/fimmu.2022.853690] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2022] [Accepted: 05/27/2022] [Indexed: 12/02/2022] Open
Abstract
The complement system is required for innate immunity against Acinetobacter baumannii, an important cause of antibiotic resistant systemic infections. A. baumannii strains differ in their susceptibility to the membrane attack complex (MAC) formed from terminal complement pathway proteins, but the reasons for this variation remain poorly understood. We have characterized in detail the complement sensitivity phenotypes of nine A. baumannii clinical strains and some of the factors that might influence differences between strains. Using A. baumannii laboratory strains and flow cytometry assays, we first reconfirmed that both opsonization with the complement proteins C3b/iC3b and MAC formation were inhibited by the capsule. There were marked differences in C3b/iC3b and MAC binding between the nine clinical A. baumannii strains, but this variation was partially independent of capsule composition or size. Opsonization with C3b/iC3b improved neutrophil phagocytosis of most strains. Importantly, although C3b/iC3b binding and MAC formation on the bacterial surface correlated closely, MAC formation did not correlate with variations between A. baumannii strains in their levels of serum resistance. Genomic analysis identified only limited differences between strains in the distribution of genes required for serum resistance, but RNAseq data identified three complement-resistance genes that were differentially regulated between a MAC resistant and two MAC intermediate resistant strains when cultured in serum. These data demonstrate that clinical A. baumannii strains vary in their sensitivity to different aspects of the complement system, and that the serum resistance phenotype was influenced by factors in addition to the amount of MAC forming on the bacterial surface.
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Affiliation(s)
- Gathoni Kamuyu
- Centre for Inflammation and Tissue Repair, UCL Respiratory, University College London, London, United Kingdom
| | - Giuseppe Ercoli
- Centre for Inflammation and Tissue Repair, UCL Respiratory, University College London, London, United Kingdom
| | - Elisa Ramos-Sevillano
- Centre for Inflammation and Tissue Repair, UCL Respiratory, University College London, London, United Kingdom
| | - Sam Willcocks
- Department of Infection Biology, London School of Hygiene and Tropical Medicine, London, United Kingdom
| | - Chidchamai Kewcharoenwong
- Department of Medical Technology, Faculty of Associated Medical Sciences, Chiang Mai University, Chiang Mai, Thailand
- Cellular and Molecular Immunology Unit, Centre for Research and Development of Medical Diagnostic Laboratories (CMDL), Faculty of Associated Medical Sciences, Khon Kaen University, Khon Kaen, Thailand
| | - Pattarachai Kiratisin
- Department of Microbiology, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok, Thailand
| | - Peter W. Taylor
- School of Pharmacy, University College London, London, United Kingdom
| | - Brendan W. Wren
- Department of Infection Biology, London School of Hygiene and Tropical Medicine, London, United Kingdom
| | - Ganjana Lertmemongkolchai
- Department of Medical Technology, Faculty of Associated Medical Sciences, Chiang Mai University, Chiang Mai, Thailand
- Cellular and Molecular Immunology Unit, Centre for Research and Development of Medical Diagnostic Laboratories (CMDL), Faculty of Associated Medical Sciences, Khon Kaen University, Khon Kaen, Thailand
| | - Richard A. Stabler
- Department of Infection Biology, London School of Hygiene and Tropical Medicine, London, United Kingdom
| | - Jeremy S. Brown
- Centre for Inflammation and Tissue Repair, UCL Respiratory, University College London, London, United Kingdom
- *Correspondence: Jeremy S. Brown,
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13
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In Vitro Activity of Rifabutin and Rifampin against Antibiotic-Resistant Acinetobacter baumannii, Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa, and Klebsiella pneumoniae. mSphere 2021; 6:e0092021. [PMID: 34817233 PMCID: PMC8612264 DOI: 10.1128/msphere.00920-21] [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] [Indexed: 11/20/2022] Open
Abstract
We recently reported that the antimicrobial activity of rifabutin against Acinetobacter baumannii is best modeled by the use of RPMI for in vitro susceptibility testing. Here, we define the effects of medium on the susceptibility and frequency of resistance emergence in a panel of A. baumannii, Escherichia coli, Staphylococcus aureus, Klebsiella pneumoniae, and Pseudomonas aeruginosa clinical isolates. Only A. baumannii was hypersusceptible to rifabutin in vitro and in vivo using a Galleria mellonella infection model. In vitro, the frequency of resistance emergence was greater when the bacteria were selected on RPMI versus tryptic soy agar (TSA) or Mueller-Hinton II (MHII) agar plates. However, the frequency of resistance emergence was lower in vivo than in the RPMI in vitro condition. IMPORTANCE Rifabutin has been recently described as a potential adjunctive therapy for antibiotic-resistant A. baumannii infections due to hypersensitivity in iron-depleted media, which may more closely mimic an in vivo environment. Here, we report that this hyperactivity is specific for A. baumannii, rather than being a general effect for other pathogens.
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14
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Abstract
Background: Extremely drug-resistant (XDR) Acinetobacter baumannii is a notorious and frequently encountered pathogen demanding novel therapeutic interventions. An initial monoclonal antibody (MAb), C8, raised against A. baumannii capsule proved a highly effective treatment against a minority of clinical isolates. To overcome this limitation, we broadened coverage by developing a second antibody for use in a combination regimen. Methods: We sought to develop an additional anti-A. baumannii MAb through hybridoma technology by immunizing mice with sublethal inocula of virulent, XDR clinical isolates not bound by MAb C8. Results: We identified a new antibacterial MAb, 65, which bound to strains in a pattern distinct from and complementary to MAb C8. MAb 65 enhanced macrophage opsonophagocytosis of targeted strains and markedly improved survival in lethal bacteremic sepsis and aspiration pneumonia murine models of A. baumannii infection. MAb 65 was also synergistic with colistin, substantially enhancing protection compared to monotherapy. Treatment with MAb 65 significantly reduced blood bacterial density, ameliorated cytokine production (IL-1β, IL-6, IL-10, and TNF), and sepsis biomarkers. Conclusions: We describe a novel MAb targeting A. baumannii that broadens immunotherapeutic strain coverage, is highly potent and effective, and synergistically improves outcomes in combination with antibiotics.
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15
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Abstract
Gram-negative bacteremia is a devastating public health threat, with high mortality in vulnerable populations and significant costs to the global economy. Concerningly, rates of both Gram-negative bacteremia and antimicrobial resistance in the causative species are increasing. Gram-negative bacteremia develops in three phases. First, bacteria invade or colonize initial sites of infection. Second, bacteria overcome host barriers, such as immune responses, and disseminate from initial body sites to the bloodstream. Third, bacteria adapt to survive in the blood and blood-filtering organs. To develop new therapies, it is critical to define species-specific and multispecies fitness factors required for bacteremia in model systems that are relevant to human infection. A small subset of species is responsible for the majority of Gram-negative bacteremia cases, including Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, and Acinetobacter baumannii The few bacteremia fitness factors identified in these prominent Gram-negative species demonstrate shared and unique pathogenic mechanisms at each phase of bacteremia progression. Capsule production, adhesins, and metabolic flexibility are common mediators, whereas only some species utilize toxins. This review provides an overview of Gram-negative bacteremia, compares animal models for bacteremia, and discusses prevalent Gram-negative bacteremia species.
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Affiliation(s)
- Caitlyn L Holmes
- Department of Pathology, University of Michigan Medical School, Ann Arbor, Michigan, USA
- Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, Michigan, USA
| | - Mark T Anderson
- Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, Michigan, USA
| | - Harry L T Mobley
- Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, Michigan, USA
| | - Michael A Bachman
- Department of Pathology, University of Michigan Medical School, Ann Arbor, Michigan, USA
- Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, Michigan, USA
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16
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Li X, Liu X, Horvatovich P, Hu Y, Zhang J. Proteomics Landscape of Host-Pathogen Interaction in Acinetobacter baumannii Infected Mouse Lung. Front Genet 2021; 12:563516. [PMID: 34025711 PMCID: PMC8138179 DOI: 10.3389/fgene.2021.563516] [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: 05/22/2020] [Accepted: 04/14/2021] [Indexed: 12/15/2022] Open
Abstract
Acinetobacter baumannii is an important pathogen of nosocomial infection worldwide, which can primarily cause pneumonia, bloodstream infection, and urinary tract infection. The increasing drug resistance rate of A. baumannii and the slow development of new antibacterial drugs brought great challenges for clinical treatment. Host immunity is crucial to the defense of A. baumannii infection, and understanding the mechanisms of immune response can facilitate the development of new therapeutic strategies. To characterize the system-level changes of host proteome in immune response, we used tandem mass tag (TMT) labeling quantitative proteomics to compare the proteome changes of lungs from A. baumannii infected mice with control mice 6 h after infection. A total of 6,218 proteins were identified in which 6,172 could be quantified. With threshold p < 0.05 and relative expression fold change > 1.2 or < 0.83, we found 120 differentially expressed proteins. Bioinformatics analysis showed that differentially expressed proteins after infection were associated with receptor recognition, NADPH oxidase (NOX) activation and antimicrobial peptides. These differentially expressed proteins were involved in the pathways including leukocyte transendothelial migration, phagocyte, neutrophil degranulation, and antimicrobial peptides. In conclusion, our study showed proteome changes in mouse lung tissue due to A. baumannii infection and suggested the important roles of NOX, neutrophils, and antimicrobial peptides in host response. Our results provide a potential list of protein candidates for the further study of host-bacteria interaction in A. baumannii infection. Data are available via ProteomeXchange with identifier PXD020640.
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Affiliation(s)
- Xin Li
- Institute of Antibiotics, Huashan Hospital, Fudan University, Shanghai, China.,Key Laboratory of Clinical Pharmacology of Antibiotics, National Health and Family Planning Commission, Shanghai, China.,National Clinical Research Center for Aging and Medicine, Huashan Hospital, Fudan University, Shanghai, China
| | - Xiaofen Liu
- Institute of Antibiotics, Huashan Hospital, Fudan University, Shanghai, China.,Key Laboratory of Clinical Pharmacology of Antibiotics, National Health and Family Planning Commission, Shanghai, China.,National Clinical Research Center for Aging and Medicine, Huashan Hospital, Fudan University, Shanghai, China
| | - Peter Horvatovich
- Department of Analytical Biochemistry, Groningen Research Institute of Pharmacy, University of Groningen, Groningen, Netherlands
| | - Yingwei Hu
- Department of Pathology, Johns Hopkins University, Baltimore, MD, United States
| | - Jing Zhang
- Institute of Antibiotics, Huashan Hospital, Fudan University, Shanghai, China.,Key Laboratory of Clinical Pharmacology of Antibiotics, National Health and Family Planning Commission, Shanghai, China.,National Clinical Research Center for Aging and Medicine, Huashan Hospital, Fudan University, Shanghai, China
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17
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Talyansky Y, Nielsen TB, Yan J, Carlino-Macdonald U, Di Venanzio G, Chakravorty S, Ulhaq A, Feldman MF, Russo TA, Vinogradov E, Luna B, Wright MS, Adams MD, Spellberg B. Capsule carbohydrate structure determines virulence in Acinetobacter baumannii. PLoS Pathog 2021; 17:e1009291. [PMID: 33529209 PMCID: PMC7880449 DOI: 10.1371/journal.ppat.1009291] [Citation(s) in RCA: 46] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2020] [Revised: 02/12/2021] [Accepted: 01/07/2021] [Indexed: 01/27/2023] Open
Abstract
Acinetobacter baumannii is a highly antibiotic-resistant bacterial pathogen for which novel therapeutic approaches are needed. Unfortunately, the drivers of virulence in A. baumannii remain uncertain. By comparing genomes among a panel of A. baumannii strains we identified a specific gene variation in the capsule locus that correlated with altered virulence. While less virulent strains possessed the intact gene gtr6, a hypervirulent clinical isolate contained a spontaneous transposon insertion in the same gene, resulting in the loss of a branchpoint in capsular carbohydrate structure. By constructing isogenic gtr6 mutants, we confirmed that gtr6-disrupted strains were protected from phagocytosis in vitro and displayed higher bacterial burden and lethality in vivo. Gtr6+ strains were phagocytized more readily and caused lower bacterial burden and no clinical illness in vivo. We found that the CR3 receptor mediated phagocytosis of gtr6+, but not gtr6-, strains in a complement-dependent manner. Furthermore, hypovirulent gtr6+ strains demonstrated increased virulence in vivo when CR3 function was abrogated. In summary, loss-of-function in a single capsule assembly gene dramatically altered virulence by inhibiting complement deposition and recognition by phagocytes across multiple A. baumannii strains. Thus, capsular structure can determine virulence among A. baumannii strains by altering bacterial interactions with host complement-mediated opsonophagocytosis.
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Affiliation(s)
- Yuli Talyansky
- Department of Molecular Microbiology & Immunology, University of Southern California, Los Angeles, California, United States of America
| | - Travis B. Nielsen
- Department of Molecular Microbiology & Immunology, University of Southern California, Los Angeles, California, United States of America
- Department of Medicine, Keck School of Medicine, University of Southern California, Los Angeles, California, United States of America
- Stritch School of Medicine, Loyola University Chicago, Maywood, Illinois, United States of America
| | - Jun Yan
- Department of Molecular Microbiology & Immunology, University of Southern California, Los Angeles, California, United States of America
| | - Ulrike Carlino-Macdonald
- Division of Infectious Diseases, Department of Medicine, Jacobs School of Medicine and Biomedical Sciences, University at Buffalo, Veterans Administration, Buffalo, New York, United States of America
| | - Gisela Di Venanzio
- Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, Missouri, United States of America
| | - Somnath Chakravorty
- Division of Infectious Diseases, Department of Medicine, Jacobs School of Medicine and Biomedical Sciences, University at Buffalo, Veterans Administration, Buffalo, New York, United States of America
| | - Amber Ulhaq
- Department of Molecular Microbiology & Immunology, University of Southern California, Los Angeles, California, United States of America
| | - Mario F. Feldman
- Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, Missouri, United States of America
| | - Thomas A. Russo
- Division of Infectious Diseases, Department of Medicine, Jacobs School of Medicine and Biomedical Sciences, University at Buffalo, Veterans Administration, Buffalo, New York, United States of America
| | - Evgeny Vinogradov
- National Research Council Canada, Human Health Therapeutics Centre, Ottawa, Canada
| | - Brian Luna
- Department of Molecular Microbiology & Immunology, University of Southern California, Los Angeles, California, United States of America
| | - Meredith S. Wright
- Rady Children’s Institute for Genomic Medicine, San Diego, California, United States of America
| | - Mark D. Adams
- The Jackson Laboratory for Genomic Medicine, Farmington, Connecticut, United States of America
| | - Brad Spellberg
- LAC+USC Medical Center, Los Angeles, California, United States of America
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18
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Sato Y, Tansho-Nagakawa S, Ubagai T, Ono Y. Analysis of Immune Responses in Acinetobacter baumannii-Infected Klotho Knockout Mice: A Mouse Model of Acinetobacter baumannii Infection in Aged Hosts. Front Immunol 2020; 11:601614. [PMID: 33329595 PMCID: PMC7719750 DOI: 10.3389/fimmu.2020.601614] [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] [Received: 09/01/2020] [Accepted: 10/27/2020] [Indexed: 12/24/2022] Open
Abstract
Acinetobacter baumannii is an important opportunistic pathogen that primarily afflicts elderly people. To clarify the pathogenicity of A. baumannii in the elderly, we investigated immune responses to A. baumannii ATCC 19606 infection in klotho knockout (KO) mice, the mouse model of aging. Following intravenous inoculation, the mice seldom displayed severe symptoms. However, the survival rate was 56% at 7 days post-infection. Bacteria were detected in the lungs of klotho KO mice but not klotho wildtype (WT) mice at 7 days post-infection. Neutrophils, eosinophils, interstitial macrophages, and monocyte/dendritic cell subset in the lungs of klotho KO mice were transiently induced after infection with A. baumannii. The number of alveolar macrophages in klotho KO mice was lower than that in klotho WT mice, except for 1 day post-infection. CD11b expression on neutrophils and alveolar macrophages in the lungs of klotho KO mice was seldom upregulated by the infection. These results suggested that immune functions eliminating bacteria in the lungs of klotho KO mice were insufficient. CD11blow conventional DC cells hardly increased in klotho KO mice infected with A. baumannii. Additionally, the production of interleukin (IL)-10 in the sera of klotho KO mice was significantly higher than that in klotho WT mice, whereas that production of interferon-gamma was not detected in the sera of klotho KO mice. These results suggested that acquired immune responses were hardly induced in klotho KO mice. IL-1β, CXCL1, CXCL2, and CCL2 expression was significantly higher in the lungs of klotho KO mice infected with A. baumannii than in those of klotho WT mice at 1 day post-infection. These results suggested that pulmonary inflammation was elicited in klotho KO mice during early infection. The expression levels of proinflammatory cytokines significantly correlated with TLR9 expression in the lungs of klotho KO mice. The collective results demonstrate an A. baumannii infection state in aged hosts and suggest that pulmonary inflammation and bacterial burden should be noted in aged hosts even in the absence of severe symptoms of A. baumannii infection.
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Affiliation(s)
- Yoshinori Sato
- Department of Microbiology and Immunology, Teikyo University School of Medicine, Tokyo, Japan
| | - Shigeru Tansho-Nagakawa
- Department of Microbiology and Immunology, Teikyo University School of Medicine, Tokyo, Japan
| | - Tsuneyuki Ubagai
- Department of Microbiology and Immunology, Teikyo University School of Medicine, Tokyo, Japan
| | - Yasuo Ono
- Department of Microbiology and Immunology, Teikyo University School of Medicine, Tokyo, Japan
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19
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Chen W. Host Innate Immune Responses to Acinetobacter baumannii Infection. Front Cell Infect Microbiol 2020; 10:486. [PMID: 33042864 PMCID: PMC7521131 DOI: 10.3389/fcimb.2020.00486] [Citation(s) in RCA: 29] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2020] [Accepted: 08/05/2020] [Indexed: 12/23/2022] Open
Abstract
Acinetobacter baumannii has emerged as a major threat to global public health and is one of the key human pathogens in healthcare (nosocomial and community-acquired)-associated infections. Moreover, A. baumannii rapidly develops resistance to multiple antibiotics and is now globally regarded as a serious multidrug resistant pathogen. There is an urgent need to develop novel vaccines and immunotherapeutics as alternatives to antibiotics for clinical management of A. baumannii infection. However, our knowledge of host immune responses to A. baumannii infection and the identification of novel therapeutic targets are significantly lacking. This review highlights the recent advances and critical gaps in our understanding how A. baumannii interacts with the host innate pattern-recognition receptors, induces a cascade of inflammatory cytokine and chemokine responses, and recruits innate immune effectors (such as neutrophils and macrophages) to the site of infection for effective control of the infection. Such knowledge will facilitate the identification of new targets for the design and development of effective therapeutics and vaccines to fight this emerging threat.
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Affiliation(s)
- Wangxue Chen
- Human Health and Therapeutics (HHT) Research Center, National Research Council Canada, Ottawa, ON, Canada.,Department of Biology, Brock University, St. Catharines, ON, Canada
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20
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Luna B, Trebosc V, Lee B, Bakowski M, Ulhaq A, Yan J, Lu P, Cheng J, Nielsen T, Lim J, Ketphan W, Eoh H, McNamara C, Skandalis N, She R, Kemmer C, Lociuro S, Dale GE, Spellberg B. A nutrient-limited screen unmasks rifabutin hyperactivity for extensively drug-resistant Acinetobacter baumannii. Nat Microbiol 2020; 5:1134-1143. [PMID: 32514072 PMCID: PMC7483275 DOI: 10.1038/s41564-020-0737-6] [Citation(s) in RCA: 28] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2020] [Accepted: 05/10/2020] [Indexed: 11/09/2022]
Abstract
Industry screens of large chemical libraries have traditionally relied on rich media to ensure rapid bacterial growth in high-throughput testing. We used eukaryotic, nutrient-limited growth media in a compound screen that unmasked a previously unknown hyperactivity of the old antibiotic, rifabutin (RBT), against highly resistant Acinetobacter baumannii. In nutrient-limited, but not rich, media, RBT was 200-fold more potent than rifampin. RBT was also substantially more effective in vivo. The mechanism of enhanced efficacy was a Trojan horse-like import of RBT, but not rifampin, through fhuE, only in nutrient-limited conditions. These results are of fundamental importance to efforts to discover antibacterial agents.
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Affiliation(s)
- Brian Luna
- Department of Molecular Microbiology and Immunology, USC Keck School of Medicine, Los Angeles, CA, USA.
| | | | - Bosul Lee
- Department of Molecular Microbiology and Immunology, USC Keck School of Medicine, Los Angeles, CA, USA
| | | | - Amber Ulhaq
- Department of Molecular Microbiology and Immunology, USC Keck School of Medicine, Los Angeles, CA, USA
| | - Jun Yan
- Department of Molecular Microbiology and Immunology, USC Keck School of Medicine, Los Angeles, CA, USA
| | - Peggy Lu
- Department of Molecular Microbiology and Immunology, USC Keck School of Medicine, Los Angeles, CA, USA
| | - Jiaqi Cheng
- Department of Molecular Microbiology and Immunology, USC Keck School of Medicine, Los Angeles, CA, USA
| | - Travis Nielsen
- Department of Molecular Microbiology and Immunology, USC Keck School of Medicine, Los Angeles, CA, USA
| | - Juhyeon Lim
- Department of Molecular Microbiology and Immunology, USC Keck School of Medicine, Los Angeles, CA, USA
| | - Warisa Ketphan
- Department of Molecular Microbiology and Immunology, USC Keck School of Medicine, Los Angeles, CA, USA
| | - Hyungjin Eoh
- Department of Molecular Microbiology and Immunology, USC Keck School of Medicine, Los Angeles, CA, USA
| | - Case McNamara
- Calibr, Scripps Research Institute, La Jolla, CA, USA
| | - Nicholas Skandalis
- Department of Medicine, USC Keck School of Medicine, Los Angeles, CA, USA
| | - Rosemary She
- Department of Pathology, USC Keck School of Medicine, Los Angeles, CA, USA
| | | | | | | | - Brad Spellberg
- Los Angeles County and University of Southern California Medical Center, Los Angeles, CA, USA.
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21
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Monem S, Furmanek-Blaszk B, Łupkowska A, Kuczyńska-Wiśnik D, Stojowska-Swędrzyńska K, Laskowska E. Mechanisms Protecting Acinetobacter baumannii against Multiple Stresses Triggered by the Host Immune Response, Antibiotics and Outside-Host Environment. Int J Mol Sci 2020; 21:E5498. [PMID: 32752093 PMCID: PMC7432025 DOI: 10.3390/ijms21155498] [Citation(s) in RCA: 36] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2020] [Revised: 07/29/2020] [Accepted: 07/30/2020] [Indexed: 02/06/2023] Open
Abstract
Acinetobacter baumannii is considered one of the most persistent pathogens responsible for nosocomial infections. Due to the emergence of multidrug resistant strains, as well as high morbidity and mortality caused by this pathogen, A. baumannii was placed on the World Health Organization (WHO) drug-resistant bacteria and antimicrobial resistance research priority list. This review summarizes current studies on mechanisms that protect A. baumannii against multiple stresses caused by the host immune response, outside host environment, and antibiotic treatment. We particularly focus on the ability of A. baumannii to survive long-term desiccation on abiotic surfaces and the population heterogeneity in A. baumannii biofilms. Insight into these protective mechanisms may provide clues for the development of new strategies to fight multidrug resistant strains of A. baumannii.
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Affiliation(s)
- Soroosh Monem
- Department of General and Medical Biochemistry, Faculty of Biology, University of Gdansk, Wita Stwosza 59, 80-308 Gdansk, Poland; (S.M.); (A.Ł.); (D.K.-W.); (K.S.-S.)
| | - Beata Furmanek-Blaszk
- Department of Microbiology, Faculty of Biology, University of Gdansk, Wita Stwosza 59, 80-308 Gdansk, Poland;
| | - Adrianna Łupkowska
- Department of General and Medical Biochemistry, Faculty of Biology, University of Gdansk, Wita Stwosza 59, 80-308 Gdansk, Poland; (S.M.); (A.Ł.); (D.K.-W.); (K.S.-S.)
| | - Dorota Kuczyńska-Wiśnik
- Department of General and Medical Biochemistry, Faculty of Biology, University of Gdansk, Wita Stwosza 59, 80-308 Gdansk, Poland; (S.M.); (A.Ł.); (D.K.-W.); (K.S.-S.)
| | - Karolina Stojowska-Swędrzyńska
- Department of General and Medical Biochemistry, Faculty of Biology, University of Gdansk, Wita Stwosza 59, 80-308 Gdansk, Poland; (S.M.); (A.Ł.); (D.K.-W.); (K.S.-S.)
| | - Ewa Laskowska
- Department of General and Medical Biochemistry, Faculty of Biology, University of Gdansk, Wita Stwosza 59, 80-308 Gdansk, Poland; (S.M.); (A.Ł.); (D.K.-W.); (K.S.-S.)
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22
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Depletion of Alveolar Macrophages Increases Pulmonary Neutrophil Infiltration, Tissue Damage, and Sepsis in a Murine Model of Acinetobacter baumannii Pneumonia. Infect Immun 2020; 88:IAI.00128-20. [PMID: 32366576 DOI: 10.1128/iai.00128-20] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2020] [Accepted: 04/30/2020] [Indexed: 12/14/2022] Open
Abstract
Acinetobacter baumannii has emerged as an important etiological agent of hospital-related infections, especially nosocomial pneumonia. The virulence factors of this bacterium and their interactions with the cells and molecules of the immune system just recently began to be extensively studied. Here, we investigated the impact of alveolar macrophages on A. baumannii pneumonia using a mouse model of infection and a flexible tissue culture system. We hypothesized that depletion of macrophages would enhance sepsis and severity of A. baumannii disease. We showed that macrophages are important for modulating the antibacterial function of neutrophils and play an important role in eradicating A. baumannii infection in vivo Our findings suggest that in the absence of macrophages in the lungs, A. baumannii replicates significantly, and host proinflammatory cytokines are considerably reduced. Neutrophils are abundantly recruited to pulmonary tissue, releasing high amounts of reactive oxygen species and causing extensive tissue damage. The ability of A. baumannii to form biofilms and resist oxidative stress in the respiratory tract facilitates systemic dissemination and ultimately death of infected C57BL/6 mice. These results provide novel information regarding A. baumannii pathogenesis and may be important for the development of therapies aimed at reducing morbidity and mortality associated with this emerging bacterial pathogen.
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23
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Papathanakos G, Andrianopoulos I, Papathanasiou A, Priavali E, Koulenti D, Koulouras V. Colistin-Resistant Acinetobacter Baumannii Bacteremia: A Serious Threat for Critically Ill Patients. Microorganisms 2020; 8:microorganisms8020287. [PMID: 32093299 PMCID: PMC7074815 DOI: 10.3390/microorganisms8020287] [Citation(s) in RCA: 29] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2020] [Revised: 02/17/2020] [Accepted: 02/18/2020] [Indexed: 01/31/2023] Open
Abstract
The prevalence of acinetobacter baumannii (AB) as a cause of hospital infections has been rising. Unfortunately, emerging colistin resistance limits therapeutic options and affects the outcome. The aim of the study was to confirm our clinically-driven hypothesis that intensive care unit (ICU) patients with AB resistant-to-colistin (ABCoR) bloodstream infection (BSI) develop fulminant septic shock and die. We conducted a 28-month retrospective observational study including all patients developing AB infection on ICU admission or during ICU stay. From 622 screened patients, 31 patients with BSI sepsis were identified. Thirteen (41.9%) patients had ABCoR BSI and 18/31 (58.1%) had colistin-susceptible (ABCoS) BSI. All ABCoR BSI patients died; of them, 69% (9/13) presented with fulminant septic shock and died within the first 3 days from its onset. ABCoR BSI patients compared to ABCoS BSI patients had higher mortality (100% vs. 50%, respectively (p = 0.001)), died sooner (p = 0.006), had lower pH (p = 0.004) and higher lactate on ICU admission (p = 0.0001), and had higher APACHE II (p = 0.01) and Charlson Comorbidity Index scores (p = 0.044). In conclusion, we documented that critically ill patients with ABCoR BSI exhibit fulminant septic shock with excessive mortality. Our results highlight the emerging clinical problem of AB colistin resistance among ICU patients.
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Affiliation(s)
- Georgios Papathanakos
- University Hospital of Ioannina, Intensive Care Unit, Stavros Niarchos Avenue, 45500 Ioannina, Greece; (I.A.); (A.P.); (V.K.)
- Correspondence: ; Tel.: +30-2651-099-353
| | - Ioannis Andrianopoulos
- University Hospital of Ioannina, Intensive Care Unit, Stavros Niarchos Avenue, 45500 Ioannina, Greece; (I.A.); (A.P.); (V.K.)
| | - Athanasios Papathanasiou
- University Hospital of Ioannina, Intensive Care Unit, Stavros Niarchos Avenue, 45500 Ioannina, Greece; (I.A.); (A.P.); (V.K.)
| | - Efthalia Priavali
- Department of Microbiology, Medical School, University of Ioannina, 45110, Ioannina, Greece
| | - Despoina Koulenti
- Burns, Trauma and Critical Care Research Centre, UQ Centre for Clinical Research (UQCCR), Faculty of Medicine, The University of Queensland, Brisbane, Herston Campus, Brisbane QLD 4029, Australia;
- 2nd Critical Care Department, Attikon University Hospital, Rimini Street, 12463, Athens, Greece
| | - Vasilios Koulouras
- University Hospital of Ioannina, Intensive Care Unit, Stavros Niarchos Avenue, 45500 Ioannina, Greece; (I.A.); (A.P.); (V.K.)
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24
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Human pleural fluid triggers global changes in the transcriptional landscape of Acinetobacter baumannii as an adaptive response to stress. Sci Rep 2019; 9:17251. [PMID: 31754169 PMCID: PMC6872806 DOI: 10.1038/s41598-019-53847-2] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2019] [Accepted: 11/06/2019] [Indexed: 12/16/2022] Open
Abstract
Acinetobacter baumannii is a feared, drug-resistant pathogen, characterized by its ability to resist extreme environmental and nutrient-deprived conditions. Previously, we showed that human serum albumin (HSA) can increase foreign DNA acquisition specifically and alter the expression of genes associated with pathogenicity. Moreover, in a recent genome-wide transcriptomic study, we observed that pleural fluid (PF), an HSA-containing fluid, increases DNA acquisition, can modulate cytotoxicity, and control immune responses by eliciting changes in the A. baumannii metabolic profile. In the present work, using more stringent criteria and focusing on the analysis of genes related to pathogenicity and response to stress, we analyzed our previous RNA-seq data and performed phenotypic assays to further explore the impact of PF on A. baumannii's microbial behavior and the strategies used to overcome environmental stress. We observed that PF triggered differential expression of genes associated with motility, efflux pumps, antimicrobial resistance, biofilm formation, two-component systems (TCSs), capsule synthesis, osmotic stress, and DNA-damage response, among other categories. Phenotypic assays of A. baumannii A118 and two other clinical A. baumannii strains, revealed differences in their responses to PF in motility, biofilm formation, antibiotic susceptibility, osmotic stress, and outer membrane vesicle (OMV) production, suggesting that these changes are strain specific. We conclude that A. baumannii's pathoadaptive responses is induced by HSA-containing fluids and must be part of this bacterium armamentarium to persist in hostile environments.
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25
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Potential Mechanisms of Mucin-Enhanced Acinetobacter baumannii Virulence in the Mouse Model of Intraperitoneal Infection. Infect Immun 2019; 87:IAI.00591-19. [PMID: 31405959 DOI: 10.1128/iai.00591-19] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2019] [Accepted: 08/07/2019] [Indexed: 12/21/2022] Open
Abstract
Porcine mucin has been commonly used to enhance the infectivity of bacterial pathogens, including Acinetobacter baumannii, in animal models, but the mechanisms for enhancement by mucin remain relatively unknown. In this study, using the mouse model of intraperitoneal (i.p.) mucin-enhanced A. baumannii infection, we characterized the kinetics of bacterial replication and dissemination and the host innate immune responses, as well as their potential contribution to mucin-enhanced bacterial virulence. We found that mucin, either admixed with or separately injected with the challenge bacterial inoculum, was able to enhance the tissue and blood burdens of A. baumannii strains of different virulence. Intraperitoneal injection of A. baumannii-mucin or mucin alone induced a significant but comparable reduction of peritoneal macrophages and lymphocytes, accompanied by a significant neutrophil recruitment and early interleukin-10 (IL-10) responses, suggesting that the resulting inflammatory cellular and cytokine responses were largely induced by the mucin. Depletion of peritoneal macrophages or neutralization of endogenous IL-10 activities showed no effect on the mucin-enhanced infectivity. However, pretreatment of mucin with iron chelator DIBI, but not deferoxamine, partially abolished its virulence enhancement ability, and replacement of mucin with iron significantly enhanced the bacterial burdens in the peritoneal cavity and lung. Taken together, our results favor the hypothesis that iron at least partially contributes to the mucin-enhanced infectivity of A. baumannii in this model.
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26
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Efficacy of ARV-1502, a Proline-Rich Antimicrobial Peptide, in a Murine Model of Bacteremia Caused by Multi-Drug Resistant (MDR) Acinetobacter baumannii. Molecules 2019; 24:molecules24152820. [PMID: 31382389 PMCID: PMC6696424 DOI: 10.3390/molecules24152820] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2019] [Revised: 07/19/2019] [Accepted: 07/30/2019] [Indexed: 11/29/2022] Open
Abstract
Acinetobacter baumannii bacteremia represents a serious and increasing clinical problem due to the high mortality and treatment failures because of high rates of antibiotic resistance. Any additional new therapies for A. baumannii bacteremia would address a growing unmet medical need. ARV-1502 (designated as Chex1-Arg20 or A3-APO monomer in prior publications) is a designer proline-rich antimicrobial peptide chaperone protein inhibitor derived from insects and has demonstrated potent activity against multi-drug resistant (MDR) Gram-negative bacteria. In the current studies, we investigated the therapeutic efficacy of ARV-1502 administered intravenously (iv) alone and in combination with imipenem/cilastatin (IPM/CIL) in a mouse bacteremia model due to a MDR clinical A. baumannii strain, HUMC1. All ARV-1502 regimens (1.25, 2.5 and 5.0 mg/kg) significantly reduced bacterial density in the target tissues in a dose-dependent manner, as compared to the untreated control and IPM/CIL monotherapy (40 mg/kg) groups in the model. In addition, ARV-1502 treatment, even at the lowest dose, significantly improved survival vs. the control and IPM alone groups. As expected, IMP/CIL monotherapy had no therapeutic efficacy in the model, since the HUMC1 strain was resistant to IMP in vitro. However, the combination of ARV-1502 and IPM/CIL significantly enhanced the efficacy of ARV-1502, except the lowest dose of ARV-1502. The superior efficacy of ARV-1502 in the bacteremia model caused by MDR A. baumannii provides further support for studying this compound in severe infections caused by other MDR Gram-positive and -negative pathogens.
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27
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Luna BM, Yan J, Reyna Z, Moon E, Nielsen TB, Reza H, Lu P, Bonomo R, Louie A, Drusano G, Bulitta J, She R, Spellberg B. Natural history of Acinetobacter baumannii infection in mice. PLoS One 2019; 14:e0219824. [PMID: 31318907 PMCID: PMC6638954 DOI: 10.1371/journal.pone.0219824] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2019] [Accepted: 07/03/2019] [Indexed: 01/30/2023] Open
Abstract
In 2017, the WHO identified Acinetobacter baumannii as the top priority for the development of new antibiotics. Despite the need for new antibiotics, there remains a lack of well validated preclinical tools for A. baumannii. Here, we characterize and validate a mouse model for A. baumannii translational research. Antibiotic sensitivity for meropenem, amikacin, and polymyxin b was determined by the broth microdilution MIC assay. LD100 inoculums, in both blood and lung infection models, were determined in male and female C3HeB/FeJ mice that were challenged with various A. baumannii clinical isolates. Blood (blood infection model) or blood and lung tissue (lung infection model) were collected from infected mice at 2 and 18 hours and the bacterial burden was determined by quantitative culture. Blood chemistry was analyzed using the iStat system. Cytokines (IL-1ß, TNF, IL-6, and IL-10) were measured in the blood and lung homogenate by ELISA assay. Lung sections (H&E stains) were scored by a pathologist. In the blood infection model, the cytokines and physiological data indicate that mice become moribund due to sepsis (low blood pH, falling bicarbonate, and a rising base deficit), whereas mice become moribund due to respiratory failure (low blood pH, rising bicarbonate, and a falling base deficit) in the oral aspiration pneumonia model. We also characterized the timing of changes in various clinical and biomarker endpoints, which can serve as a basis for future interventional studies. Susceptibility was generally similar across gender and infection route. However, we did observe that female mice were approximately 2-fold more sensitive to LAC-4 ColR in the blood infection model. We also observed that female mice were more than 10-fold more resistant to VA-AB41 in the oral aspiration pneumonia model. These results establish parameters to follow in order to assess efficacy of novel preventative and therapeutic approaches for these infections.
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Affiliation(s)
- Brian M. Luna
- Department of Medicine, Keck School of Medicine at the University of Southern California (USC), Los Angeles, California, United States of America
- Department of Molecular Microbiology and Immunology, Keck School of Medicine at the University of Southern California (USC), Los Angeles, California, United States of America
- * E-mail:
| | - Jun Yan
- Department of Medicine, Keck School of Medicine at the University of Southern California (USC), Los Angeles, California, United States of America
- Department of Molecular Microbiology and Immunology, Keck School of Medicine at the University of Southern California (USC), Los Angeles, California, United States of America
| | - Zeferino Reyna
- Department of Pathology, Keck School of Medicine at the University of Southern California (USC), Los Angeles, California, United States of America
| | - Eugene Moon
- Department of Medicine, Keck School of Medicine at the University of Southern California (USC), Los Angeles, California, United States of America
- Department of Molecular Microbiology and Immunology, Keck School of Medicine at the University of Southern California (USC), Los Angeles, California, United States of America
| | - Travis B. Nielsen
- Department of Medicine, Keck School of Medicine at the University of Southern California (USC), Los Angeles, California, United States of America
- Department of Molecular Microbiology and Immunology, Keck School of Medicine at the University of Southern California (USC), Los Angeles, California, United States of America
| | - Hernan Reza
- Department of Medicine, Keck School of Medicine at the University of Southern California (USC), Los Angeles, California, United States of America
- Department of Molecular Microbiology and Immunology, Keck School of Medicine at the University of Southern California (USC), Los Angeles, California, United States of America
| | - Peggy Lu
- Department of Medicine, Keck School of Medicine at the University of Southern California (USC), Los Angeles, California, United States of America
- Department of Molecular Microbiology and Immunology, Keck School of Medicine at the University of Southern California (USC), Los Angeles, California, United States of America
| | - Robert Bonomo
- Departments of Medicine, Pharmacology, and Molecular Biology and Microbiology, Louis Stokes Cleveland Department of Veterans Affairs Medical Center, Case Western Reserve University, Cleveland, Ohio, United States of America
| | - Arnold Louie
- Center for Pharmacometrics & Systems Pharmacology, Department of Pharmaceutics, College of Pharmacy, University of Florida, Orlando, Florida, United States of America
| | - George Drusano
- Institute for Therapeutic Innovation, College of Medicine, University of Florida, Orlando, Florida, United States of America
| | - Jürgen Bulitta
- Center for Pharmacometrics & Systems Pharmacology, Department of Pharmaceutics, College of Pharmacy, University of Florida, Orlando, Florida, United States of America
| | - Rosemary She
- Department of Pathology, Keck School of Medicine at the University of Southern California (USC), Los Angeles, California, United States of America
| | - Brad Spellberg
- Department of Medicine, Keck School of Medicine at the University of Southern California (USC), Los Angeles, California, United States of America
- Department of Molecular Microbiology and Immunology, Keck School of Medicine at the University of Southern California (USC), Los Angeles, California, United States of America
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28
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Rodman N, Martinez J, Fung S, Nakanouchi J, Myers AL, Harris CM, Dang E, Fernandez JS, Liu C, Mendoza AM, Jimenez V, Nikolaidis N, Brennan CA, Bonomo RA, Sieira R, Ramirez MS. Human Pleural Fluid Elicits Pyruvate and Phenylalanine Metabolism in Acinetobacter baumannii to Enhance Cytotoxicity and Immune Evasion. Front Microbiol 2019; 10:1581. [PMID: 31379769 PMCID: PMC6650585 DOI: 10.3389/fmicb.2019.01581] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2019] [Accepted: 06/25/2019] [Indexed: 01/13/2023] Open
Abstract
Acinetobacter baumannii (Ab) is one of the most treacherous pathogens among those causing hospital-acquired pneumonia (HAP). A. baumannii possesses an adaptable physiology, seen not only in its antibiotic resistance and virulence phenotypes but also in its metabolic versatility. In this study, we observed that A. baumannii undergoes global transcriptional changes in response to human pleural fluid (PF), a key host-derived environmental signal. Differential gene expression analyses combined with experimental approaches revealed changes in A. baumannii metabolism, affecting cytotoxicity, persistence, bacterial killing, and chemotaxis. Over 1,220 genes representing 55% of the differentially expressed transcriptomic data corresponded to metabolic processes, including the upregulation of glutamate, short chain fatty acid, and styrene metabolism. We observed an upregulation by 1.83- and 2.61-fold of the pyruvate dehydrogenase complex subunits E3 and E2, respectively. We also found that pyruvate (PYR), in conjunction with PF, triggers an A. baumannii pathogenic behavior that adversely impacts human epithelial cell viability. Interestingly, PF also amplified A. baumannii cytotoxicity against murine macrophages, suggesting an immune evasion strategy implemented by A. baumannii. Moreover, we uncovered opposing metabolic strategies dependent on the degree of pathogenicity of the strains, where less pathogenic strains demonstrated greater utilization of PYR to promote persister formation in the presence of PF. Additionally, our transcriptomic analysis and growth studies of A. baumannii suggest the existence of an alternative phenylalanine (PA) catabolic route independent of the phenylacetic acid pathway, which converts PA to phenylpyruvate (PP) and shuttles intermediates into styrene metabolism. This alternative route promoted a neutrophil-evasive state, as PF-induced degradation of PP significantly reduced overall human neutrophil chemotaxis in ex vivo chemotactic assays. Taken together, these data highlight A. baumannii pathoadaptabililty in response to host signals and provide further insight into the role of bacterial metabolism in virulence traits, antibiotic persistence strategies, and host innate immune evasion.
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Affiliation(s)
- Nyah Rodman
- Center for Applied Biotechnology Studies, Department of Biological Science, College of Natural Sciences and Mathematics, California State University, Fullerton, Fullerton, CA, United States
| | - Jasmine Martinez
- Center for Applied Biotechnology Studies, Department of Biological Science, College of Natural Sciences and Mathematics, California State University, Fullerton, Fullerton, CA, United States
| | - Sammie Fung
- Center for Applied Biotechnology Studies, Department of Biological Science, College of Natural Sciences and Mathematics, California State University, Fullerton, Fullerton, CA, United States
| | - Jun Nakanouchi
- Center for Applied Biotechnology Studies, Department of Biological Science, College of Natural Sciences and Mathematics, California State University, Fullerton, Fullerton, CA, United States
| | - Amber L Myers
- Center for Applied Biotechnology Studies, Department of Biological Science, College of Natural Sciences and Mathematics, California State University, Fullerton, Fullerton, CA, United States
| | - Caitlin M Harris
- Center for Applied Biotechnology Studies, Department of Biological Science, College of Natural Sciences and Mathematics, California State University, Fullerton, Fullerton, CA, United States
| | - Emily Dang
- Center for Applied Biotechnology Studies, Department of Biological Science, College of Natural Sciences and Mathematics, California State University, Fullerton, Fullerton, CA, United States
| | - Jennifer S Fernandez
- Center for Applied Biotechnology Studies, Department of Biological Science, College of Natural Sciences and Mathematics, California State University, Fullerton, Fullerton, CA, United States
| | - Christine Liu
- Center for Applied Biotechnology Studies, Department of Biological Science, College of Natural Sciences and Mathematics, California State University, Fullerton, Fullerton, CA, United States
| | - Anthony M Mendoza
- Center for Applied Biotechnology Studies, Department of Biological Science, College of Natural Sciences and Mathematics, California State University, Fullerton, Fullerton, CA, United States
| | - Veronica Jimenez
- Center for Applied Biotechnology Studies, Department of Biological Science, College of Natural Sciences and Mathematics, California State University, Fullerton, Fullerton, CA, United States
| | - Nikolas Nikolaidis
- Center for Applied Biotechnology Studies, Department of Biological Science, College of Natural Sciences and Mathematics, California State University, Fullerton, Fullerton, CA, United States
| | - Catherine A Brennan
- Center for Applied Biotechnology Studies, Department of Biological Science, College of Natural Sciences and Mathematics, California State University, Fullerton, Fullerton, CA, United States
| | - Robert A Bonomo
- Medical Service and Geriatrics Research, Education and Clinical Center (GRECC), Louis Stokes Cleveland Department of Veterans Affairs Medical Center, Cleveland, OH, United States.,Departments of Medicine, Pharmacology, Molecular Biology and Microbiology, Biochemistry, Proteomics and Bioinformatics, Case Western Reserve University School of Medicine, Cleveland, OH, United States.,CWRU-Cleveland VAMC Center for Antimicrobial Resistance and Epidemiology (Case VA CARES), Cleveland, OH, United States
| | - Rodrigo Sieira
- Fundacioìn Instituto Leloir-IIBBA CONICET, Buenos Aires, Argentina
| | - Maria Soledad Ramirez
- Center for Applied Biotechnology Studies, Department of Biological Science, College of Natural Sciences and Mathematics, California State University, Fullerton, Fullerton, CA, United States
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29
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Morris FC, Dexter C, Kostoulias X, Uddin MI, Peleg AY. The Mechanisms of Disease Caused by Acinetobacter baumannii. Front Microbiol 2019; 10:1601. [PMID: 31379771 PMCID: PMC6650576 DOI: 10.3389/fmicb.2019.01601] [Citation(s) in RCA: 155] [Impact Index Per Article: 31.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2019] [Accepted: 06/26/2019] [Indexed: 01/29/2023] Open
Abstract
Acinetobacter baumannii is a Gram negative opportunistic pathogen that has demonstrated a significant insurgence in the prevalence of infections over recent decades. With only a limited number of “traditional” virulence factors, the mechanisms underlying the success of this pathogen remain of great interest. Major advances have been made in the tools, reagents, and models to study A. baumannii pathogenesis, and this has resulted in a substantial increase in knowledge. This article provides a comprehensive review of the bacterial virulence factors, the host immune responses, and animal models applicable for the study of this important human pathogen. Collating the most recent evidence characterizing bacterial virulence factors, their cellular targets and genetic regulation, we have encompassed numerous aspects important to the success of this pathogen, including membrane proteins and cell surface adaptations promoting immune evasion, mechanisms for nutrient acquisition and community interactions. The role of innate and adaptive immune responses is reviewed and areas of paucity in our understanding are highlighted. Finally, with the vast expansion of available animal models over recent years, we have evaluated those suitable for use in the study of Acinetobacter disease, discussing their advantages and limitations.
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Affiliation(s)
- Faye C Morris
- Infection and Immunity Program, Department of Microbiology, Monash Biomedicine Discovery Institute, Monash University, Clayton, VIC, Australia
| | - Carina Dexter
- Infection and Immunity Program, Department of Microbiology, Monash Biomedicine Discovery Institute, Monash University, Clayton, VIC, Australia
| | - Xenia Kostoulias
- Infection and Immunity Program, Department of Microbiology, Monash Biomedicine Discovery Institute, Monash University, Clayton, VIC, Australia
| | - Muhammad Ikhtear Uddin
- Infection and Immunity Program, Department of Microbiology, Monash Biomedicine Discovery Institute, Monash University, Clayton, VIC, Australia
| | - Anton Y Peleg
- Infection and Immunity Program, Department of Microbiology, Monash Biomedicine Discovery Institute, Monash University, Clayton, VIC, Australia.,Department of Infectious Diseases, The Alfred Hospital and Central Clinical School, Monash University, Melbourne, VIC, Australia
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30
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Harris G, KuoLee R, Xu HH, Chen W. Acute intraperitoneal infection with a hypervirulent Acinetobacter baumannii isolate in mice. Sci Rep 2019; 9:6538. [PMID: 31024025 PMCID: PMC6484084 DOI: 10.1038/s41598-019-43000-4] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2019] [Accepted: 04/09/2019] [Indexed: 12/05/2022] Open
Abstract
Acinetobacter baumannii infection has become a major cause of healthcare-associated infection and a critical pathogen in the WHO antimicrobial resistance research and development priority list. Catheter-related septicemia is one of the major clinical manifestations of A. baumannii infection associated with high morbidity and mortality. In this study, we used a clinical A. baumannii strain (LAC-4) that is hypervirulent to immunocompetent C57BL/6 and BALB/c mice and established a mouse model of intraperitoneal (i.p.) A. baumannii infection. Our study showed that i.p. LAC-4 infection of C57BL/6 and BALB/c mice induces a lethal or sublethal infection with high bacterial burdens in peritoneal cavity, blood and tissues and the infected mice either succumbed to the infection within 24 hours or completely recovered from the infection. The infection induces acute peritoneal recruitment of neutrophils and other innate immune cells, and the local and systemic production of proinflammatory cytokines and chemokines (IL-1β, IL-5, IL-6, TNF-α, RANTES, MIP-1β, MCP-1, KC and IL-10). Mechanistic studies suggest an important role of macrophages in the host innate defense in this model in that in vitro stimulation of peritoneal macrophages with killed LAC-4 induced a similar pattern of cytokine/chemokine responses to those in the infected mice, and depletion of peritoneal macrophages rendered the mice significantly more susceptible to the infection. Thus, this mouse infection model will provide an alternative and useful tool for future pathogenesis studies of A. baumannii-associated septicemia and identification and characterization of important virulence factors, as well as serve as a surrogate model for rapid evaluation of novel therapeutics and vaccines for this emerging infectious agent.
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Affiliation(s)
- Greg Harris
- Human Health Therapeutics Research Center, National Research Council Canada, 100 Sussex Drive, Ottawa, Ontario, K1A 0R6, Canada
| | - Rhonda KuoLee
- Human Health Therapeutics Research Center, National Research Council Canada, 100 Sussex Drive, Ottawa, Ontario, K1A 0R6, Canada
| | - H Howard Xu
- Department of Biological Sciences, California State University, Los Angeles, Los Angeles, CA, 90032, USA
| | - Wangxue Chen
- Human Health Therapeutics Research Center, National Research Council Canada, 100 Sussex Drive, Ottawa, Ontario, K1A 0R6, Canada. .,Department of Biology, Brock University, St. Catharines, Ontario, L2S 3A1, Canada.
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31
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Pires S, Parker D. Innate Immune Responses to Acinetobacter baumannii in the Airway. J Interferon Cytokine Res 2019; 39:441-449. [PMID: 31013462 DOI: 10.1089/jir.2019.0008] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Acinetobacter baumannii is an emerging opportunistic pathogen that has risen to become a serious global threat, prevalent in health care settings and the community, which results in high morbidity and mortality rates. Its alarming expansion of antibiotic resistance is one of the most problematic traits of A. baumannii and as so, this bacterium has been classified as a serious threat and high priority target by the CDC. The most common types of infections induced by this pathogen include pneumonia (both hospital and community acquired), bacteremia, skin and soft tissue, urinary tract infections, endocarditis, and meningitis. Nosocomial pneumonia is the most prevalent of these. This review summarizes the current state of the signaling and innate immune components activated in response to A. baumannii infection in the airway.
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Affiliation(s)
- Sílvia Pires
- Department of Pathology and Laboratory Medicine, Center for Immunity and Inflammation, Rutgers New Jersey Medical School, Newark, New Jersey
| | - Dane Parker
- Department of Pathology and Laboratory Medicine, Center for Immunity and Inflammation, Rutgers New Jersey Medical School, Newark, New Jersey
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32
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SERPINB1-mediated checkpoint of inflammatory caspase activation. Nat Immunol 2019; 20:276-287. [PMID: 30692621 DOI: 10.1038/s41590-018-0303-z] [Citation(s) in RCA: 73] [Impact Index Per Article: 14.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2017] [Accepted: 12/14/2018] [Indexed: 02/07/2023]
Abstract
Inflammatory caspases (caspase-1, caspase-4, caspase-5 and caspase-11 (caspase-1/-4/-5/-11)) mediate host defense against microbial infections, processing pro-inflammatory cytokines and triggering pyroptosis. However, precise checkpoints are required to prevent their unsolicited activation. Here we report that serpin family B member 1 (SERPINB1) limited the activity of those caspases by suppressing their caspase-recruitment domain (CARD) oligomerization and enzymatic activation. While the reactive center loop of SERPINB1 inhibits neutrophil serine proteases, its carboxy-terminal CARD-binding motif restrained the activation of pro-caspase-1/-4/-5/-11. Consequently, knockdown or deletion of SERPINB1 prompted spontaneous activation of caspase-1/-4/-5/-11, release of the cytokine IL-1β and pyroptosis, inducing elevated inflammation after non-hygienic co-housing with pet-store mice and enhanced sensitivity to lipopolysaccharide- or Acinetobacter baumannii-induced endotoxemia. Our results reveal that SERPINB1 acts as a vital gatekeeper of inflammation by restraining neutrophil serine proteases and inflammatory caspases in a genetically and functionally separable manner.
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33
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Liu Y, Mi Z, Mi L, Huang Y, Li P, Liu H, Yuan X, Niu W, Jiang N, Bai C, Gao Z. Identification and characterization of capsule depolymerase Dpo48 from Acinetobacter baumannii phage IME200. PeerJ 2019; 7:e6173. [PMID: 30656071 PMCID: PMC6336015 DOI: 10.7717/peerj.6173] [Citation(s) in RCA: 34] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2018] [Accepted: 11/28/2018] [Indexed: 12/16/2022] Open
Abstract
Background The emergence of multidrug- or extensively drug-resistant Acinetobacter baumannii has made it difficult to treat and control infections caused by this bacterium. It is urgently necessary to search for alternatives to conventional antibiotics for control of severe A. baumannii infections. In recent years, bacteriophages and their derivatives, such as depolymerases, showed great potential as antibacterial or antivirulence agents against bacterial infections. Nonetheless, unlike broad-spectrum bactericidal antibiotics, phage-encoded depolymerase targets only a limited number of bacterial strains. Therefore, identification of novel depolymerases and evaluation of their ability to control A. baumannii infections is important. Methods A bacteriophage was isolated from hospital sewage using an extensively drug-resistant A. baumannii strain as the host bacterium, and the phage’s plaque morphology and genomic composition were studied. A polysaccharide depolymerase (Dpo48) was expressed and identified, and the effects of pH and temperature on its activity were determined. Besides, a serum killing assay was conducted, and amino acid sequences homologous to those of putative polysaccharide depolymerases were compared. Results Phage IME200 yielded clear plaques surrounded by enlarged halos, with polysaccharide depolymerase activity against the host bacterium. A tail fiber protein with a Pectate_lyase_3 domain was identified as Dpo48 and characterized . Dpo48 was found to degrade the capsule polysaccharide of the bacterial surface, as revealed by Alcian blue staining. Dpo48 manifested stable activity over a broad range of pH (5.0–9.0) and temperatures (20–70 °C). Results from in vitro serum killing assays indicated that 50% serum was sufficient to cause a five log reduction of overnight enzyme-treated bacteria, with serum complement playing an important role in these killing assays. Moreover, Dpo48 had a spectrum of activity exactly the same as its parental phage IME200, which was active against 10 out of 41 A. baumannii strains. Amino acid sequence alignment showed that the putative tail fiber proteins had a relatively short, highly conserved domain in their N-terminal sequences, but their amino acid sequences containing pectate lyase domains, found in the C-terminal regions, were highly diverse. Conclusions Phage-encoded capsule depolymerases may become promising antivirulence agents for preventing and controlling A. baumannii infections.
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Affiliation(s)
- Yannan Liu
- Department of Respiratory and Critical Care Medicine, Peking University People's Hospital, Beijing, China.,Department of Respiratory and Critical Care Medicine, 307th Hospital of PLA, Beijing, China
| | - Zhiqiang Mi
- State Key Laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Beijing, China
| | - Liyuan Mi
- State Key Laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Beijing, China
| | - Yong Huang
- State Key Laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Beijing, China
| | - Puyuan Li
- Department of Respiratory and Critical Care Medicine, 307th Hospital of PLA, Beijing, China
| | - Huiying Liu
- Department of Respiratory and Critical Care Medicine, 307th Hospital of PLA, Beijing, China
| | - Xin Yuan
- Department of Respiratory and Critical Care Medicine, 307th Hospital of PLA, Beijing, China
| | - Wenkai Niu
- Department of Respiratory and Critical Care Medicine, 307th Hospital of PLA, Beijing, China
| | - Ning Jiang
- Department of Respiratory and Critical Care Medicine, Peking University People's Hospital, Beijing, China
| | - Changqing Bai
- Department of Respiratory and Critical Care Medicine, 307th Hospital of PLA, Beijing, China
| | - Zhancheng Gao
- Department of Respiratory and Critical Care Medicine, Peking University People's Hospital, Beijing, China
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Zurawski DV, Black CC, Alamneh YA, Biggemann L, Banerjee J, Thompson MG, Wise MC, Honnold CL, Kim RK, Paranavitana C, Shearer JP, Tyner SD, Demons ST. A Porcine Wound Model of Acinetobacter baumannii Infection. Adv Wound Care (New Rochelle) 2019; 8:14-27. [PMID: 30705786 PMCID: PMC6350066 DOI: 10.1089/wound.2018.0786] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2018] [Accepted: 06/24/2018] [Indexed: 01/25/2023] Open
Abstract
Objective: To better understand Acinetobacter baumannii pathogenesis and to advance drug discovery against this pathogen, we developed a porcine, full-thickness, excisional, monospecies infection wound model. Approach: The research was facilitated with AB5075, a previously characterized, extensively drug-resistant A. baumannii isolate. The model requires cyclophosphamide-induced neutropenia to establish a skin and soft tissue infection (SSTI) that persists beyond 7 days. Multiple, 12-mm-diameter full-thickness wounds were created in the skin overlying the cervical and thoracic dorsum. Wound beds were inoculated with 5.0 × 104 colony-forming units (CFU) and covered with dressing. Results:A. baumannii was observed in the wound bed and on the dressing in what appeared to be biofilm. When bacterial burdens were measured, proliferation to at least 106 CFU/g (log106) wound tissue was observed. Infection was further characterized by scanning electron microscopy (SEM) and peptide nucleic acid fluorescence in situ hybridization (PNA-FISH) staining. To validate as a treatment model, polymyxin B was applied topically to a subset of infected wounds every 2 days. Then, the treated and untreated wounds were compared using multiple quantitative and qualitative techniques to include gross pathology, CFU burden, histopathology, PNA-FISH, and SEM. Innovation: This is the first study to use A. baumannii in a porcine model as the sole infectious agent. Conclusion: The porcine model allows for an additional preclinical assessment of antibacterial candidates that show promise against A. baumannii in rodent models, further evaluating safety and efficacy, and serve as a large animal in preclinical assessment for the treatment of SSTI.
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Affiliation(s)
- Daniel V. Zurawski
- Wound Infections Department, Bacterial Diseases Branch, Walter Reed Army Institute of Research, Silver Spring, Maryland
| | - Chad C. Black
- Experimental Therapeutics Branch, Walter Reed Army Institute of Research, Silver Spring, Maryland
| | - Yonas A. Alamneh
- Wound Infections Department, Bacterial Diseases Branch, Walter Reed Army Institute of Research, Silver Spring, Maryland
| | - Lionel Biggemann
- Wound Infections Department, Bacterial Diseases Branch, Walter Reed Army Institute of Research, Silver Spring, Maryland
| | - Jaideep Banerjee
- Wound Infections Department, Bacterial Diseases Branch, Walter Reed Army Institute of Research, Silver Spring, Maryland
| | - Mitchell G. Thompson
- Wound Infections Department, Bacterial Diseases Branch, Walter Reed Army Institute of Research, Silver Spring, Maryland
| | - Matthew C. Wise
- Veterinary Services Program, Department of Pathology, Walter Reed Army Institute of Research, Silver Spring, Maryland
| | - Cary L. Honnold
- Veterinary Services Program, Department of Pathology, Walter Reed Army Institute of Research, Silver Spring, Maryland
| | - Robert K. Kim
- Wound Infections Department, Bacterial Diseases Branch, Walter Reed Army Institute of Research, Silver Spring, Maryland
| | - Chrysanthi Paranavitana
- Wound Infections Department, Bacterial Diseases Branch, Walter Reed Army Institute of Research, Silver Spring, Maryland
| | - Jonathan P. Shearer
- Wound Infections Department, Bacterial Diseases Branch, Walter Reed Army Institute of Research, Silver Spring, Maryland
| | - Stuart D. Tyner
- Wound Infections Department, Bacterial Diseases Branch, Walter Reed Army Institute of Research, Silver Spring, Maryland
| | - Samandra T. Demons
- Wound Infections Department, Bacterial Diseases Branch, Walter Reed Army Institute of Research, Silver Spring, Maryland
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Nishida S, Ono Y. Comparative analysis of the pathogenicity between multidrug-resistant Acinetobacter baumannii clinical isolates: isolation of highly pathogenic multidrug-resistant A. baumannii and experimental therapeutics with fourth-generation cephalosporin cefozopran. Infect Drug Resist 2018; 11:1715-1722. [PMID: 30349328 PMCID: PMC6188165 DOI: 10.2147/idr.s166154] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Introduction The pathogenicity of fatal-outbreak Acinetobacter baumannii isolates has not been fully investigated. This study aimed to compare the pathogenicity between A. baumannii clinical isolates, including multidrug-resistant A. baumannii (MDRA). Materials and methods Antibiotic susceptibility was determined by the broth microdilution method, and drug-resistant genes were characterized by PCR and sequencing. The pathogenicity of A. baumannii and antibiotic responses were evaluated using the Galleria mellonella infection model. Clinical isolates from an A. baumannii outbreak at our hospital were categorized using the pulse-field gel electrophoresis. Of the 16 isolated A. baumannii clones, 12 clones were resistant to carbapenems (meropenem and imipenem), of which 10 clones were also resistant to amikacin and ciprofloxacin (MDRAs). MDRAs had OXA-51-like β-lactamase gene harboring an insertion sequence in the promoter region and armA gene encoding 16S rRNA methyltransferase. Results Carbapenem- and/or amikacin-resistant A. baumannii were more pathogenic than carbapenem- and/or amikacin-sensitive A. baumannii in G. mellonella. MDRA isolate TK1033 was more virulent than other A. baumannii isolates. However, TK1033 was sensitive to the fourth-generation cephalosporin cefozopran in addition to minocycline, tigecycline, and polymyxins (colistin and polymyxins B) in vitro and in vivo in the MDRA-G. mellonella infection model. Conclusion Differences in pathogenicity among carbapenem-resistant A. baumannii clones are consistent with heterogeneous clinical outcomes. Strain TK1033, isolated frequently during the outbreak, was the most virulent, whereas preoutbreak isolate TK1032 was less virulent than other A. baumannii isolates. Infection by high-virulence isolates may be more prevalent during outbreaks. These strains may prove valuable for investigating MDRA virulence and novel therapeutics.
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Affiliation(s)
- Satoshi Nishida
- Department of Microbiology and Immunology, Teikyo University School of Medicine, Itabashi, Tokyo, Japan,
| | - Yasuo Ono
- Department of Microbiology and Immunology, Teikyo University School of Medicine, Itabashi, Tokyo, Japan,
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Geisinger E, Mortman NJ, Vargas-Cuebas G, Tai AK, Isberg RR. A global regulatory system links virulence and antibiotic resistance to envelope homeostasis in Acinetobacter baumannii. PLoS Pathog 2018; 14:e1007030. [PMID: 29795704 PMCID: PMC5967708 DOI: 10.1371/journal.ppat.1007030] [Citation(s) in RCA: 62] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2017] [Accepted: 04/16/2018] [Indexed: 11/19/2022] Open
Abstract
The nosocomial pathogen Acinetobacter baumannii is a significant threat due to its ability to cause infections refractory to a broad range of antibiotic treatments. We show here that a highly conserved sensory-transduction system, BfmRS, mediates the coordinate development of both enhanced virulence and resistance in this microorganism. Hyperactive alleles of BfmRS conferred increased protection from serum complement killing and allowed lethal systemic disease in mice. BfmRS also augmented resistance and tolerance against an expansive set of antibiotics, including dramatic protection from β-lactam toxicity. Through transcriptome profiling, we showed that BfmRS governs these phenotypes through global transcriptional regulation of a post-exponential-phase-like program of gene expression, a key feature of which is modulation of envelope biogenesis and defense pathways. BfmRS activity defended against cell-wall lesions through both β-lactamase-dependent and -independent mechanisms, with the latter being connected to control of lytic transglycosylase production and proper coordination of morphogenesis and division. In addition, hypersensitivity of bfmRS knockouts could be suppressed by unlinked mutations restoring a short, rod cell morphology, indicating that regulation of drug resistance, pathogenicity, and envelope morphogenesis are intimately linked by this central regulatory system in A. baumannii. This work demonstrates that BfmRS controls a global regulatory network coupling cellular physiology to the ability to cause invasive, drug-resistant infections. Infections with the hospital-acquired bacterium Acinetobacter baumannii are highly difficult to treat. The pathogen has evolved multiple lines of defense against antimicrobial stress, including a barrier-forming cell envelope as well as control systems that respond to antimicrobial stresses by enhancing antibiotic resistance and virulence. Here, we uncovered the role of a key stress-response system, BfmRS, in controlling the transition of A. baumannii to a state of heightened resistance and virulence. We show that BfmRS enhances pathogenicity in mammalian hosts, and augments the ability to grow in the presence of diverse antibiotics and tolerate transient, high-level antibiotic exposures. Connected to these effects is the ability of BfmRS to globally reprogram gene expression and control multiple pathways that build, protect, and shape the cell envelope. Moreover, we determined that resistance-enhancing mutations bypassing the need for BfmRS also modulate envelope- and morphology-associated pathways, further linking control of physiology with resistance in A. baumannii. This work uncovers a global control circuit that shifts cellular physiology in ways that promote hospital-associated disease, and points to inhibition of this circuit as a potential strategy for disarming the pathogen.
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Affiliation(s)
- Edward Geisinger
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, Massachusetts, United States of America
- Howard Hughes Medical Institute, Boston, Massachusetts, United States of America
| | - Nadav J. Mortman
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, Massachusetts, United States of America
| | - Germán Vargas-Cuebas
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, Massachusetts, United States of America
| | - Albert K. Tai
- Department of Integrative Physiology and Pathobiology, Tufts University School of Medicine, Boston, Massachusetts, United States of America
| | - Ralph R. Isberg
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, Massachusetts, United States of America
- Howard Hughes Medical Institute, Boston, Massachusetts, United States of America
- * E-mail:
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Kale SD, Dikshit N, Kumar P, Balamuralidhar V, Khameneh HJ, Bin Abdul Malik N, Koh TH, Tan GGY, Tan TT, Mortellaro A, Sukumaran B. Nod2 is required for the early innate immune clearance of Acinetobacter baumannii from the lungs. Sci Rep 2017; 7:17429. [PMID: 29234083 PMCID: PMC5727160 DOI: 10.1038/s41598-017-17653-y] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2017] [Accepted: 11/19/2017] [Indexed: 12/19/2022] Open
Abstract
Acinetobacter baumannii (A. baumannii) is a significant cause of severe nosocomial pneumonia in immunocompromised individuals world-wide. With limited treatment options available, a better understanding of host immnity to A. baumannii infection is critical to devise alternative control strategies. Our previous study has identified that intracellular Nod1/Nod2 signaling pathway is required for the immune control of A. baumannii in airway epithelial cells in vitro. In the current study, using Nod2−/− mice and an in vivo sublethal model of pulmonary infection, we show that Nod2 contributes to the early lung defense against A. baumannii infection through reactive oxygen species (ROS)/reactive nitrogen species (RNS) production as Nod2−/− mice showed significantly reduced production of ROS/RNS in the lungs following A. baumannii infection. Consistent with the higher bacterial load, A. baumannii-induced neutrophil recruitment, cytokine/chemokine response and lung pathology was also exacerbated in Nod2−/− mice at early time points post-infection. Finally, we show that administration of Nod2 ligand muramyl dipeptide (MDP) prior to infection protected the wild- type mice from A. baumannii pulmonary challenge. Collectively, Nod2 is an important player in the early lung immunity against A. baumannii and modulating Nod2 pathway could be considered as a viable therapeutic strategy to control A. baumannii pulmonary infection.
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Affiliation(s)
- Sandeep D Kale
- Program in Emerging Infectious Diseases, Duke-NUS Medical School, Singapore, 169857, Singapore
| | - Neha Dikshit
- Program in Emerging Infectious Diseases, Duke-NUS Medical School, Singapore, 169857, Singapore
| | - Pankaj Kumar
- Program in Emerging Infectious Diseases, Duke-NUS Medical School, Singapore, 169857, Singapore
| | | | - Hanif Javanmard Khameneh
- Singapore Immunology Network (SIgN), Agency for Science, Technology and Research (A*STAR), Singapore, 138648, Singapore
| | - Najib Bin Abdul Malik
- Program in Emerging Infectious Diseases, Duke-NUS Medical School, Singapore, 169857, Singapore
| | - Tse Hsien Koh
- Department of Microbiology, Division of Pathology, Singapore General Hospital, Singapore, Singapore
| | | | - Thuan Tong Tan
- Department of Infectious Diseases, Singapore General Hospital, Singapore, Singapore
| | - Alessandra Mortellaro
- Singapore Immunology Network (SIgN), Agency for Science, Technology and Research (A*STAR), Singapore, 138648, Singapore
| | - Bindu Sukumaran
- Program in Emerging Infectious Diseases, Duke-NUS Medical School, Singapore, 169857, Singapore.
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Nielsen TB, Pantapalangkoor P, Luna BM, Bruhn KW, Yan J, Dekitani K, Hsieh S, Yeshoua B, Pascual B, Vinogradov E, Hujer KM, Domitrovic TN, Bonomo RA, Russo TA, Lesczcyniecka M, Schneider T, Spellberg B. Monoclonal Antibody Protects Against Acinetobacter baumannii Infection by Enhancing Bacterial Clearance and Evading Sepsis. J Infect Dis 2017; 216:489-501. [PMID: 28931235 DOI: 10.1093/infdis/jix315] [Citation(s) in RCA: 59] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2017] [Accepted: 06/30/2017] [Indexed: 01/01/2023] Open
Abstract
Background Extremely drug-resistant (XDR) Acinetobacter baumannii is one of the most commonly encountered, highly resistant pathogens requiring novel therapeutic interventions. Methods We developed C8, a monoclonal antibody (mAb), by immunizing mice with sublethal inocula of a hypervirulent XDR clinical isolate. Results C8 targets capsular carbohydrate on the bacterial surface, enhancing opsonophagocytosis. Treating with a single dose of C8 as low as 0.5 μg/mouse (0.0167 mg/kg) markedly improved survival in lethal bacteremic sepsis and aspiration pneumonia models of XDR A. baumannii infection. C8 was also synergistic with colistin, substantially improving survival compared to monotherapy. Treatment with C8 significantly reduced blood bacterial density, cytokine production (tumor necrosis factor α, interleukin [IL] 6, IL-1β, and IL-10), and sepsis biomarkers. Serial in vitro passaging of A. baumannii in the presence of C8 did not cause loss of mAb binding to the bacteria, but did result in emergence of less-virulent mutants that were more susceptible to macrophage uptake. Finally, we developed a highly humanized variant of C8 that retains opsonophagocytic activity in murine and human macrophages and rescued mice from lethal infection. Conclusions We describe a promising and novel mAb as therapy for lethal, XDR A. baumannii infections, and demonstrate that it synergistically improves outcomes in combination with antibiotics.
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Affiliation(s)
- Travis B Nielsen
- Department of Medicine and Department of Molecular Microbiology and Immunology, Keck School of Medicine, University of Southern California, Los Angeles
| | - Paul Pantapalangkoor
- Department of Medicine and Department of Molecular Microbiology and Immunology, Keck School of Medicine, University of Southern California, Los Angeles
| | - Brian M Luna
- Department of Medicine and Department of Molecular Microbiology and Immunology, Keck School of Medicine, University of Southern California, Los Angeles
| | - Kevin W Bruhn
- Department of Medicine and Department of Molecular Microbiology and Immunology, Keck School of Medicine, University of Southern California, Los Angeles
| | - Jun Yan
- Department of Medicine and Department of Molecular Microbiology and Immunology, Keck School of Medicine, University of Southern California, Los Angeles
| | - Ken Dekitani
- Department of Medicine and Department of Molecular Microbiology and Immunology, Keck School of Medicine, University of Southern California, Los Angeles
| | - Sarah Hsieh
- Department of Medicine and Department of Molecular Microbiology and Immunology, Keck School of Medicine, University of Southern California, Los Angeles
| | - Brandon Yeshoua
- Department of Medicine and Department of Molecular Microbiology and Immunology, Keck School of Medicine, University of Southern California, Los Angeles
| | - Bryan Pascual
- Department of Medicine and Department of Molecular Microbiology and Immunology, Keck School of Medicine, University of Southern California, Los Angeles
| | | | - Kristine M Hujer
- Louis Stokes Cleveland Veterans Affairs Medical Center.,Department of Medicine
| | | | - Robert A Bonomo
- Louis Stokes Cleveland Veterans Affairs Medical Center.,Department of Medicine.,Departments of Pharmacology, Molecular Biology and Microbiology, Biochemistry, and Proteomics and Bioinformatics, Case Western Reserve University, Cleveland, Ohio
| | - Thomas A Russo
- Veterans Administration Western New York Healthcare System, and the Departments of Medicine and Microbiology and Immunology, and Witebsky Center for Microbial Pathogenesis, University at Buffalo-State University of New York, Buffalo, New York
| | | | | | - Brad Spellberg
- Department of Medicine and Department of Molecular Microbiology and Immunology, Keck School of Medicine, University of Southern California, Los Angeles
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Clinical and Pathophysiological Overview of Acinetobacter Infections: a Century of Challenges. Clin Microbiol Rev 2017; 30:409-447. [PMID: 27974412 DOI: 10.1128/cmr.00058-16] [Citation(s) in RCA: 608] [Impact Index Per Article: 86.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
Acinetobacter is a complex genus, and historically, there has been confusion about the existence of multiple species. The species commonly cause nosocomial infections, predominantly aspiration pneumonia and catheter-associated bacteremia, but can also cause soft tissue and urinary tract infections. Community-acquired infections by Acinetobacter spp. are increasingly reported. Transmission of Acinetobacter and subsequent disease is facilitated by the organism's environmental tenacity, resistance to desiccation, and evasion of host immunity. The virulence properties demonstrated by Acinetobacter spp. primarily stem from evasion of rapid clearance by the innate immune system, effectively enabling high bacterial density that triggers lipopolysaccharide (LPS)-Toll-like receptor 4 (TLR4)-mediated sepsis. Capsular polysaccharide is a critical virulence factor that enables immune evasion, while LPS triggers septic shock. However, the primary driver of clinical outcome is antibiotic resistance. Administration of initially effective therapy is key to improving survival, reducing 30-day mortality threefold. Regrettably, due to the high frequency of this organism having an extreme drug resistance (XDR) phenotype, early initiation of effective therapy is a major clinical challenge. Given its high rate of antibiotic resistance and abysmal outcomes (up to 70% mortality rate from infections caused by XDR strains in some case series), new preventative and therapeutic options for Acinetobacter spp. are desperately needed.
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40
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Geisinger E, Isberg RR. Interplay Between Antibiotic Resistance and Virulence During Disease Promoted by Multidrug-Resistant Bacteria. J Infect Dis 2017; 215:S9-S17. [PMID: 28375515 DOI: 10.1093/infdis/jiw402] [Citation(s) in RCA: 95] [Impact Index Per Article: 13.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Diseases caused by antibiotic-resistant bacteria in hospitals are the outcome of complex relationships between several dynamic factors, including bacterial pathogenicity, the fitness costs of resistance in the human host, and selective forces resulting from interventions such as antibiotic therapy. The emergence and fate of mutations that drive antibiotic resistance are governed by these interactions. In this review, we will examine how different forms of antibiotic resistance modulate bacterial fitness and virulence potential, thus influencing the ability of pathogens to evolve in the context of nosocomial infections. We will focus on 3 important multidrug-resistant pathogens that are notoriously problematic in hospitals: Pseudomonas aeruginosa, Acinetobacter baumannii, and Staphylococcus aureus. An understanding of how antibiotic resistance mutations shape the pathobiology of multidrug-resistant infections has the potential to drive novel strategies that can control the development and spread of drug resistance.
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Affiliation(s)
- Edward Geisinger
- Howard Hughes Medical Institute, and.,Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, Massachusetts
| | - Ralph R Isberg
- Howard Hughes Medical Institute, and.,Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, Massachusetts
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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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García-Patiño MG, García-Contreras R, Licona-Limón P. The Immune Response against Acinetobacter baumannii, an Emerging Pathogen in Nosocomial Infections. Front Immunol 2017; 8:441. [PMID: 28446911 PMCID: PMC5388700 DOI: 10.3389/fimmu.2017.00441] [Citation(s) in RCA: 59] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2016] [Accepted: 03/29/2017] [Indexed: 12/18/2022] Open
Abstract
Acinetobacter baumannii is the etiologic agent of a wide range of nosocomial infections, including pneumonia, bacteremia, and skin infections. Over the last 45 years, an alarming increase in the antibiotic resistance of this opportunistic microorganism has been reported, a situation that hinders effective treatments. In order to develop effective therapies against A. baumannii it is crucial to understand the basis of host–bacterium interactions, especially those concerning the immune response of the host. Different innate immune cells such as monocytes, macrophages, dendritic cells, and natural killer cells have been identified as important effectors in the defense against A. baumannii; among them, neutrophils represent a key immune cell indispensable for the control of the infection. Several immune strategies to combat A. baumannii have been identified such as recognition of the bacteria by immune cells through pattern recognition receptors, specifically toll-like receptors, which trigger bactericidal mechanisms including oxidative burst and cytokine and chemokine production to amplify the immune response against the pathogen. However, a complete picture of the protective immune strategies activated by this bacteria and its potential therapeutic use remains to be determined and explored.
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Affiliation(s)
- María Guadalupe García-Patiño
- Departamento de Biología Celular y del Desarrollo, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Ciudad de México, Mexico
| | - Rodolfo García-Contreras
- Facultad de Medicina, Departamento de Microbiología y Parasitología, Universidad Nacional Autónoma de México, Ciudad de México, Mexico
| | - Paula Licona-Limón
- Departamento de Biología Celular y del Desarrollo, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Ciudad de México, Mexico
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Miller SE, Bell CS, McClain MS, Cover TL, Giorgio TD. Dynamic Computational Model of Symptomatic Bacteremia to Inform Bacterial Separation Treatment Requirements. PLoS One 2016; 11:e0163167. [PMID: 27657881 PMCID: PMC5033423 DOI: 10.1371/journal.pone.0163167] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2016] [Accepted: 09/02/2016] [Indexed: 11/21/2022] Open
Abstract
The rise of multi-drug resistance has decreased the effectiveness of antibiotics, which has led to increased mortality rates associated with symptomatic bacteremia, or bacterial sepsis. To combat decreasing antibiotic effectiveness, extracorporeal bacterial separation approaches have been proposed to capture and separate bacteria from blood. However, bacteremia is dynamic and involves host-pathogen interactions across various anatomical sites. We developed a mathematical model that quantitatively describes the kinetics of pathogenesis and progression of symptomatic bacteremia under various conditions, including bacterial separation therapy, to better understand disease mechanisms and quantitatively assess the biological impact of bacterial separation therapy. Model validity was tested against experimental data from published studies. This is the first multi-compartment model of symptomatic bacteremia in mammals that includes extracorporeal bacterial separation and antibiotic treatment, separately and in combination. The addition of an extracorporeal bacterial separation circuit reduced the predicted time of total bacteria clearance from the blood of an immunocompromised rodent by 49%, compared to antibiotic treatment alone. Implementation of bacterial separation therapy resulted in predicted multi-drug resistant bacterial clearance from the blood of a human in 97% less time than antibiotic treatment alone. The model also proposes a quantitative correlation between time-dependent bacterial load among tissues and bacteremia severity, analogous to the well-known ‘area under the curve’ for characterization of drug efficacy. The engineering-based mathematical model developed may be useful for informing the design of extracorporeal bacterial separation devices. This work enables the quantitative identification of the characteristics required of an extracorporeal bacteria separation device to provide biological benefit. These devices will potentially decrease the bacterial load in blood. Additionally, the devices may achieve bacterial separation rates that allow consequent acceleration of bacterial clearance in other tissues, inhibiting the progression of symptomatic bacteremia, including multi-drug resistant variations.
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Affiliation(s)
- Sinead E. Miller
- Department of Biomedical Engineering, Vanderbilt University, Nashville, Tennessee, United States of America
| | - Charleson S. Bell
- Department of Biomedical Engineering, Vanderbilt University, Nashville, Tennessee, United States of America
| | - Mark S. McClain
- Department of Medicine, Division of Infectious Disease, Vanderbilt University Medical Center, Nashville, Tennessee, United States of America
| | - Timothy L. Cover
- Department of Medicine, Division of Infectious Disease, Vanderbilt University Medical Center, Nashville, Tennessee, United States of America
- Veterans Affairs Tennessee Valley Healthcare System, Nashville, Tennessee, United States of America
| | - Todd D. Giorgio
- Department of Biomedical Engineering, Vanderbilt University, Nashville, Tennessee, United States of America
- * E-mail:
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Chen W. Current advances and challenges in the development of Acinetobacter vaccines. Hum Vaccin Immunother 2016; 11:2495-500. [PMID: 26158773 DOI: 10.1080/21645515.2015.1052354] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
Acinetobacter baumannii is a major cause of healthcare-associated infections worldwide with high morbidity and mortality. The clinical treatment of A. baumannii infections has become increasingly difficult because of the rapid emerging of multidrug and extremely drug resistant strains. Thus, there is an urgent need for the development of novel intervention strategies to combat this multidrug-resistant pathogen. Vaccine is one of the most effective medical measures for infection control and is likely to overcome the development of multidrug resistance by A. baumannii. Here we discussed the recent advances and potential challenges in development of A. baumannii vaccines with a focus on the 3 most important steps in the preclinical vaccine development: antigen selection, immune correlates of protection, and animal models for efficacy evaluation.
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Affiliation(s)
- Wangxue Chen
- a Human Health Therapeutics; National Research Council Canada ; Ottawa, Ontario , Canada.,b Department of Biology ; Brock University ; St. Catharines , Ontario , Canada
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The Response Regulator BfmR Is a Potential Drug Target for Acinetobacter baumannii. mSphere 2016; 1:mSphere00082-16. [PMID: 27303741 PMCID: PMC4888885 DOI: 10.1128/msphere.00082-16] [Citation(s) in RCA: 64] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2016] [Accepted: 04/12/2016] [Indexed: 11/24/2022] Open
Abstract
Increasing antibiotic resistance in bacteria, particularly Gram-negative bacilli, has significantly affected the ability of physicians to treat infections, with resultant increased morbidity, mortality, and health care costs. In fact, some strains of bacteria are resistant to all available antibiotics, such as Acinetobacter baumannii, which is the focus of this report. Therefore, the development of new antibiotics active against these resistant strains is urgently needed. In this study, BfmR is further validated as an intriguing target for a novel class of antibiotics. Successful inactivation of BfmR would confer the multiple benefits of a decreased ability of A. baumannii to survive in human body fluids, increased sensitivity to complement-mediated bactericidal activity and, importantly, increased sensitivity to other antibiotics. Structural studies support the potential for this “druggable” target, as they identify the potential for small-molecule binding at functionally relevant sites. Next-phase high-throughput screening studies utilizing BfmR are warranted. Identification and validation is the first phase of target-based antimicrobial development. BfmR (RstA), a response regulator in a two-component signal transduction system (TCS) in Acinetobacter baumannii, is an intriguing potential antimicrobial target. A unique characteristic of BfmR is that its inhibition would have the dual benefit of significantly decreasing in vivo survival and increasing sensitivity to selected antimicrobials. Studies on the clinically relevant strain AB307-0294 have shown BfmR to be essential in vivo. Here, we demonstrate that this phenotype in strains AB307-0294 and AB908 is mediated, in part, by enabling growth in human ascites fluid and serum. Further, BfmR conferred resistance to complement-mediated bactericidal activity that was independent of capsular polysaccharide. Importantly, BfmR also increased resistance to the clinically important antimicrobials meropenem and colistin. BfmR was highly conserved among A. baumannii strains. The crystal structure of the receiver domain of BfmR was determined, lending insight into putative ligand binding sites. This enabled an in silico ligand binding analysis and a blind docking strategy to assess use as a potential druggable target. Predicted binding hot spots exist at the homodimer interface and the phosphorylation site. These data support pursuing the next step in the development process, which includes determining the degree of inhibition needed to impact growth/survival and the development a BfmR activity assay amenable to high-throughput screening for the identification of inhibitors. Such agents would represent a new class of antimicrobials active against A. baumannii which could be active against other Gram-negative bacilli that possess a TCS with shared homology. IMPORTANCE Increasing antibiotic resistance in bacteria, particularly Gram-negative bacilli, has significantly affected the ability of physicians to treat infections, with resultant increased morbidity, mortality, and health care costs. In fact, some strains of bacteria are resistant to all available antibiotics, such as Acinetobacter baumannii, which is the focus of this report. Therefore, the development of new antibiotics active against these resistant strains is urgently needed. In this study, BfmR is further validated as an intriguing target for a novel class of antibiotics. Successful inactivation of BfmR would confer the multiple benefits of a decreased ability of A. baumannii to survive in human body fluids, increased sensitivity to complement-mediated bactericidal activity and, importantly, increased sensitivity to other antibiotics. Structural studies support the potential for this “druggable” target, as they identify the potential for small-molecule binding at functionally relevant sites. Next-phase high-throughput screening studies utilizing BfmR are warranted.
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Acinetobacter baumannii Infection and IL-17 Mediated Immunity. Mediators Inflamm 2016; 2016:9834020. [PMID: 26977122 PMCID: PMC4762998 DOI: 10.1155/2016/9834020] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2015] [Accepted: 01/11/2016] [Indexed: 01/25/2023] Open
Abstract
Acinetobacter baumannii is a significant cause of severe hospital-acquired infections with a recent rise in multidrug-resistant infections involving traumatic wounds of military personnel. The interleukin-17 (IL-17) pathway is essential for neutrophil recruitment in response to a variety of pathogens, while the control of A. baumannii infection is known to be dependent on neutrophils. This suggests that IL-17 may play an important role in A. baumannii infection; however, this has yet to be studied. Here, we summarize the recent advances in understanding the host-pathogen interaction of A. baumannii and propose a potential role of the IL-17 pathway in generating a protective immune response.
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Bruhn KW, Dekitani K, Nielsen TB, Pantapalangkoor P, Spellberg B. Ly6G-mediated depletion of neutrophils is dependent on macrophages. RESULTS IN IMMUNOLOGY 2015; 6:5-7. [PMID: 26870635 PMCID: PMC4711394 DOI: 10.1016/j.rinim.2015.12.001] [Citation(s) in RCA: 49] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/05/2015] [Revised: 11/10/2015] [Accepted: 12/17/2015] [Indexed: 02/08/2023]
Abstract
Antibody-mediated depletion of neutrophils is commonly used to study neutropenia. However, the mechanisms by which antibodies deplete neutrophils have not been well defined. We noticed that mice deficient in complement and macrophages had blunted neutrophil depletion in response to anti-Ly6G monoclonal antibody (MAb) treatment. In vitro, exposure of murine neutrophils to anti-Ly6G MAb in the presence of plasma did not result in significant depletion of cells, either in the presence or absence of complement. In vivo, anti-Ly6G-mediated neutrophil depletion was abrogated following macrophage depletion, but not complement depletion, indicating a requirement for macrophages to induce neutropenia by this method. These results inform the use and limitations of anti-Ly6G antibody as an experimental tool for depleting neutrophils in various immunological settings. In vivo depletion of mouse neutrophils by anti-Ly6G antibody requires macrophages. Plasma is not sufficient for anti-Ly6G-mediated neutrophil depletion in vitro. Anti-Ly6G depletes neutrophils in mice without active complement.
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Affiliation(s)
- Kevin W Bruhn
- Department of Molecular Microbiology and Immunology, Keck School of Medicine at the University of Southern California (USC), Los Angeles, CA, USA
| | - Ken Dekitani
- Department of Molecular Microbiology and Immunology, Keck School of Medicine at the University of Southern California (USC), Los Angeles, CA, USA
| | - Travis B Nielsen
- Department of Molecular Microbiology and Immunology, Keck School of Medicine at the University of Southern California (USC), Los Angeles, CA, USA
| | - Paul Pantapalangkoor
- Department of Molecular Microbiology and Immunology, Keck School of Medicine at the University of Southern California (USC), Los Angeles, CA, USA
| | - Brad Spellberg
- Division of Infectious Diseases, Keck School of Medicine at USC, Los Angeles, CA, USA
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Koenigs A, Stahl J, Averhoff B, Göttig S, Wichelhaus TA, Wallich R, Zipfel PF, Kraiczy P. CipA of Acinetobacter baumannii Is a Novel Plasminogen Binding and Complement Inhibitory Protein. J Infect Dis 2015; 213:1388-99. [PMID: 26681776 DOI: 10.1093/infdis/jiv601] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2015] [Accepted: 12/03/2015] [Indexed: 01/08/2023] Open
Abstract
Acinetobacter baumannii is an emerging opportunistic pathogen, responsible for up to 10% of gram-negative, nosocomial infections. The global increase of multidrug-resistant and pan-resistant Acinetobacter isolates presents clinicians with formidable challenges. To establish a persistent infection,A. baumannii must overcome the detrimental effects of complement as the first line of defense against invading microorganisms. However, the immune evasion principles underlying serum resistance inA. baumannii remain elusive. Here, we identified a novel plasminogen-binding protein, termed CipA. Bound plasminogen, upon conversion to active plasmin, degraded fibrinogen and complement C3b and contributed to serum resistance. Furthermore, CipA directly inhibited the alternative pathway of complement in vitro, irrespective of its ability to bind plasminogen. A CipA-deficient mutant was efficiently killed by human serum and showed a defect in the penetration of endothelial monolayers, demonstrating that CipA is a novel multifunctional protein that contributes to the pathogenesis ofA. baumannii.
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Affiliation(s)
- Arno Koenigs
- Institute of Medical Microbiology and Infection Control, University Hospital of Frankfurt
| | - Julia Stahl
- Department of Molecular Microbiology and Bioenergetics, Institute of Molecular Biosciences, Goethe University, Frankfurt
| | - Beate Averhoff
- Department of Molecular Microbiology and Bioenergetics, Institute of Molecular Biosciences, Goethe University, Frankfurt
| | - Stephan Göttig
- Institute of Medical Microbiology and Infection Control, University Hospital of Frankfurt
| | - Thomas A Wichelhaus
- Institute of Medical Microbiology and Infection Control, University Hospital of Frankfurt
| | | | - Peter F Zipfel
- Department of Infection Biology, Leibniz Institute for Natural Product Research and Infection Biology Friedrich Schiller University, Jena, Germany
| | - Peter Kraiczy
- Institute of Medical Microbiology and Infection Control, University Hospital of Frankfurt
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Cryopreservation of virulent Acinetobacter baumannii to reduce variability of in vivo studies. BMC Microbiol 2015; 15:252. [PMID: 26526621 PMCID: PMC4630970 DOI: 10.1186/s12866-015-0580-8] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2015] [Accepted: 10/22/2015] [Indexed: 11/23/2022] Open
Abstract
Background Microbiological assays require accurate and reproducible preparation of bacterial inocula. Inocula prepared on different days by different individuals can vary significantly from experiment to experiment. This variance is particularly problematic for Gram-negative bacterial infections, for which threshold effects can result in marked variations in host outcome with minor differences in inocula. Results We compared the accuracy of traditional methods versus using frozen stocks for preparing Acinetobacter baumannii inocula for infection in mice. Standard inoculum preparation resulted in substantial variability, both with respect to the actual inocula achieved compared to the targeted inocula, and with respect to the in vivo outcome resulting from similar inocula. Cryopreservation of the bacteria resulted in no significant decrement in growth of the bacteria. Furthermore, preparation of multiple infectious inocula from a frozen stock significantly improved the accuracy of the achieved inocula, and resulted in more reproducible in vivo outcomes from infection. Frozen stocks reduced inter-experiment variability associated with inoculum preparation, displayed no significant loss of growth capacity, and maintained virulence, increasing the reliability of infection. Conclusions Frozen stocks require considerably less time to prepare and enhance reproducibility of in vivo experimental results when infecting with A. baumannii.
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Grguric-Smith LM, Lee HH, Gandhi JA, Brennan MB, DeLeon-Rodriguez CM, Coelho C, Han G, Martinez LR. Neutropenia exacerbates infection by Acinetobacter baumannii clinical isolates in a murine wound model. Front Microbiol 2015; 6:1134. [PMID: 26528277 PMCID: PMC4607880 DOI: 10.3389/fmicb.2015.01134] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2015] [Accepted: 10/02/2015] [Indexed: 01/21/2023] Open
Abstract
The Gram negative coccobacillus Acinetobacter baumannii has become an increasingly prevalent cause of hospital-acquired infections in recent years. The majority of clinical A. baumannii isolates display high-level resistance to antimicrobials, which severely compromises our capacity to care for patients with A. baumannii disease. Neutrophils are of major importance in the host defense against microbial infections. However, the contribution of these cells of innate immunity in host resistance to cutaneous A. baumannii infection has not been directly investigated. Hence, we hypothesized that depletion of neutrophils increases severity of bacterial disease in an experimental A. baumannii murine wound model. In this study, the Ly-6G-specific monoclonal antibody (mAb), 1A8, was used to generate neutropenic mice and the pathogenesis of several A. baumannii clinical isolates on wounded cutaneous tissue was investigated. We demonstrated that neutrophil depletion enhances bacterial burden using colony forming unit determinations. Also, mAb 1A8 reduces global measurements of wound healing in A. baumannii-infected animals. Interestingly, histological analysis of cutaneous tissue excised from A. baumannii-infected animals treated with mAb 1A8 displays enhanced collagen deposition. Furthermore, neutropenia and A. baumannii infection alter pro-inflammatory cytokine release leading to severe microbial disease. Our findings provide a better understanding of the impact of these innate immune cells in controlling A. baumannii skin infections.
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Affiliation(s)
| | - Hiu H Lee
- Department of Biomedical Sciences, Long Island University-Post Brookville, NY, USA ; Department of Biomedical Sciences, College of Osteopathic Medicine, New York Institute of Technology Old Westbury, NY, USA
| | - Jay A Gandhi
- Department of Biomedical Sciences, Long Island University-Post Brookville, NY, USA
| | - Melissa B Brennan
- Department of Biomedical Sciences, Long Island University-Post Brookville, NY, USA
| | | | - Carolina Coelho
- Centre for Molecular & Cellular Biology of Inflammation, Kings College London, UK
| | - George Han
- Montefiore Medical Center, Division of Dermatology, Department of Medicine Bronx, NY, USA
| | - Luis R Martinez
- Department of Biomedical Sciences, College of Osteopathic Medicine, New York Institute of Technology Old Westbury, NY, USA
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