1
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Ellison TJ, Ellison CK. DNA binding is rate-limiting for natural transformation. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.06.06.597730. [PMID: 38895488 PMCID: PMC11185590 DOI: 10.1101/2024.06.06.597730] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/21/2024]
Abstract
Bacteria take up environmental DNA using dynamic appendages called type IV pili (T4P) to elicit horizontal gene transfer in a process called natural transformation. Natural transformation is widespread amongst bacteria yet determining how different factors universally contribute to or limit this process across species has remained challenging. Here we show that Acinetobacter baylyi, the most naturally transformable species, is highly transformable due to its ability to robustly bind nonspecific DNA via a dedicated orphan minor pilin, FimT. We show that, compared to its homologues, A. baylyi FimT contains multiple positively charged residues that additively promote DNA binding efficiency. Expression of A. baylyi FimT in a closely related Acinetobacter pathogen is sufficient to substantially improve its capacity for natural transformation, demonstrating that T4P-DNA binding is a rate-limiting step in this process. These results demonstrate the importance of T4P-DNA binding efficiency in driving natural transformation, establishing a key factor limiting horizontal gene transfer.
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2
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Yilmaz I, Ozbek T. Genome editing in Acinetobacter baumannii through enhanced natural transformation. J Basic Microbiol 2024; 64:e2300644. [PMID: 38412427 DOI: 10.1002/jobm.202300644] [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: 10/28/2023] [Revised: 01/29/2024] [Accepted: 02/03/2024] [Indexed: 02/29/2024]
Abstract
Acinetobacter baumannii, a multidrug-resistant bacterium has become a significant cause of life-threatening infections acquired in hospitals worldwide. The existing drugs used to treat A. baumannii infections are rapidly losing efficacy, and the increasing antimicrobial resistance, which is expected to turn into a global health crisis, underscores the urgency to develop novel prevention and treatment strategies. We reasoned that the discovery of novel virulence targets for vaccine and therapy interventions requires a more enhanced method for the introduction of multiple elements of foreign DNA for genome editing than the current methods of natural transformation techniques. Herein, we employed a novel and a much-improved enhanced technique for the natural transformation of elements of the genome editing system CRISPR-Cas9 to suppress specific genomic regions linked to selectively suppress bacterial virulence. We modified the genome of the laboratory-adapted strain of A. baumannii BAA-747 by targeting the AmpC, as a marker gene, for disruption by three different genomic manipulation strategies, and created mutant strains of A. baumannii that are, at least, fourfold susceptible to ampicillin. This work has established an optimized enhanced natural transformation system that enables efficient genome editing of pathogenic bacteria in a laboratory setting, providing a valuable future tool for exploring the function of unidentified virulence genes in bacterial genomes.
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Affiliation(s)
- Ilknur Yilmaz
- Department of Molecular Biology and Genetics, Graduate School of Science & Engineering, Yildiz Technical University, Istanbul, Turkey
| | - Tulin Ozbek
- Department of Molecular Biology and Genetics, Faculty of Arts and Sciences, Yildiz Technical University, Istanbul, Turkey
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3
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Savin M, Sib E, Heinemann C, Eichel VM, Nurjadi D, Klose M, Andre Hammerl J, Binsker U, Mutters NT. Tracing clinically-relevant antimicrobial resistances in Acinetobacter baumannii-calcoaceticus complex across diverse environments: A study spanning clinical, livestock, and wastewater treatment settings. ENVIRONMENT INTERNATIONAL 2024; 186:108603. [PMID: 38547543 DOI: 10.1016/j.envint.2024.108603] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/18/2023] [Revised: 03/13/2024] [Accepted: 03/23/2024] [Indexed: 04/26/2024]
Abstract
Acinetobacter baumannii has become a prominent nosocomial pathogen, primarily owing to its remarkable ability to rapidly acquire resistance to a wide range of antimicrobial agents and its ability to persist in diverse environments. However, there is a lack of data on the molecular epidemiology and its potential implications for public health of A. baumannii strains exhibiting clinically significant resistances that originate from non-clinical environments. Therefore, the genetic characteristics and resistance mechanisms of 80 A. baumannii-calcoaceticus (ABC) complex isolates, sourced from environments associated with poultry and pig production, municipal wastewater treatment plants (WWTPs), and clinical settings, were investigated. In total, our study classified 54 isolates into 29 previously described sequence types (STs), while 26 isolates exhibited as-yet-unassigned STs. We identified a broad range of A. baumannii STs originating from poultry and pig production environments (e.g., ST10, ST238, ST240, ST267, ST345, ST370, ST372, ST1112 according to Pasteur scheme). These STs have also been documented in clinical settings worldwide, highlighting their clinical significance. These findings also raise concerns about the potential zoonotic transmission of certain STs associated with livestock environments. Furthermore, we observed that clinical isolates exhibited the highest diversity of antimicrobial resistance genes (ARGs). In contrast to non-clinical isolates, clinical isolates typically carried a significantly higher number of ARGs, ranging from 10 to 15. They were also the exclusive carriers of biocide resistance genes and acquired carbapenemases (blaOXA-23, blaOXA-58, blaOXA-72, blaGIM-1, blaNDM-1). Additionally, we observed that clinical strains displayed an increased capacity for carrying plasmids and undergoing genetic transformation. This heightened capability could be linked to the intense selective pressures commonly found within clinical settings. Our study provides comprehensive insights into essential aspects of ABC isolates originating from livestock-associated environments and clinical settings. We explored their resistance mechanisms and potential implications for public health, providing valuable knowledge for addressing these critical issues.
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Affiliation(s)
- Mykhailo Savin
- Institute for Hygiene and Public Health, University Hospital Bonn, Bonn, Germany.
| | - Esther Sib
- Institute for Hygiene and Public Health, University Hospital Bonn, Bonn, Germany
| | | | - Vanessa M Eichel
- Section for Hospital Hygiene and Environmental Health, Center for Infectious Diseases, University Hospital Heidelberg, Heidelberg, Germany
| | - Dennis Nurjadi
- Department of Infectious Diseases and Microbiology, University of Lübeck and University Medical Center Schleswig-Holstein Campus Lübeck, Lübeck, Germany
| | - Marian Klose
- Institute for Hygiene and Public Health, University Hospital Bonn, Bonn, Germany
| | - Jens Andre Hammerl
- Department for Biological Safety, German Federal Institute for Risk Assessment, Berlin, Germany
| | - Ulrike Binsker
- Department for Biological Safety, German Federal Institute for Risk Assessment, Berlin, Germany
| | - Nico T Mutters
- Institute for Hygiene and Public Health, University Hospital Bonn, Bonn, Germany
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4
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Vesel N, Iseli C, Guex N, Lemopoulos A, Blokesch M. DNA modifications impact natural transformation of Acinetobacter baumannii. Nucleic Acids Res 2023; 51:5661-5677. [PMID: 37178001 PMCID: PMC10287943 DOI: 10.1093/nar/gkad377] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2023] [Revised: 04/22/2023] [Accepted: 04/28/2023] [Indexed: 05/15/2023] Open
Abstract
Acinetobacter baumannii is a dangerous nosocomial pathogen, especially due to its ability to rapidly acquire new genetic traits, including antibiotic resistance genes (ARG). In A. baumannii, natural competence for transformation, one of the primary modes of horizontal gene transfer (HGT), is thought to contribute to ARG acquisition and has therefore been intensively studied. However, knowledge regarding the potential role of epigenetic DNA modification(s) on this process remains lacking. Here, we demonstrate that the methylome pattern of diverse A. baumannii strains differs substantially and that these epigenetic marks influence the fate of transforming DNA. Specifically, we describe a methylome-dependent phenomenon that impacts intra- and inter-species DNA exchange by the competent A. baumannii strain A118. We go on to identify and characterize an A118-specific restriction-modification (RM) system that impairs transformation when the incoming DNA lacks a specific methylation signature. Collectively, our work contributes towards a more holistic understanding of HGT in this organism and may also aid future endeavors towards tackling the spread of novel ARGs. In particular, our results suggest that DNA exchanges between bacteria that share similar epigenomes are favored and could therefore guide future research into identifying the reservoir(s) of dangerous genetic traits for this multi-drug resistant pathogen.
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Affiliation(s)
- Nina Vesel
- Laboratory of Molecular Microbiology, Global Health Institute, School of Life Sciences, Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
| | - Christian Iseli
- Bioinformatics Competence Center, Ecole Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland
- Bioinformatics Competence Center, University of Lausanne, CH-1015 Lausanne, Switzerland
| | - Nicolas Guex
- Bioinformatics Competence Center, Ecole Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland
- Bioinformatics Competence Center, University of Lausanne, CH-1015 Lausanne, Switzerland
| | - Alexandre Lemopoulos
- Laboratory of Molecular Microbiology, Global Health Institute, School of Life Sciences, Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
| | - Melanie Blokesch
- Laboratory of Molecular Microbiology, Global Health Institute, School of Life Sciences, Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
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5
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Marutescu LG. Current and Future Flow Cytometry Applications Contributing to Antimicrobial Resistance Control. Microorganisms 2023; 11:1300. [PMID: 37317273 DOI: 10.3390/microorganisms11051300] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2023] [Revised: 05/10/2023] [Accepted: 05/11/2023] [Indexed: 06/16/2023] Open
Abstract
Antimicrobial resistance is a global threat to human health and welfare, food safety, and environmental health. The rapid detection and quantification of antimicrobial resistance are important for both infectious disease control and public health threat assessment. Technologies such as flow cytometry can provide clinicians with the early information, they need for appropriate antibiotic treatment. At the same time, cytometry platforms facilitate the measurement of antibiotic-resistant bacteria in environments impacted by human activities, enabling assessment of their impact on watersheds and soils. This review focuses on the latest applications of flow cytometry for the detection of pathogens and antibiotic-resistant bacteria in both clinical and environmental samples. Novel antimicrobial susceptibility testing frameworks embedding flow cytometry assays can contribute to the implementation of global antimicrobial resistance surveillance systems that are needed for science-based decisions and actions.
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Affiliation(s)
- Luminita Gabriela Marutescu
- Department of Botany and Microbiology, Faculty of Biology, University of Bucharest, 91-95 Spl. Independentei, 050095 Bucharest, Romania
- Research Institute of the University of Bucharest, 050095 Bucharest, Romania
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6
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Valcek A, Philippe C, Whiteway C, Robino E, Nesporova K, Bové M, Coenye T, De Pooter T, De Coster W, Strazisar M, Van der Henst C. Phenotypic Characterization and Heterogeneity among Modern Clinical Isolates of Acinetobacter baumannii. Microbiol Spectr 2023; 11:e0306122. [PMID: 36475894 PMCID: PMC9927488 DOI: 10.1128/spectrum.03061-22] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2022] [Accepted: 11/22/2022] [Indexed: 12/13/2022] Open
Abstract
Acinetobacter baumannii is an opportunistic pathogenic bacterium prioritized by WHO and CDC because of its increasing antibiotic resistance. Heterogeneity among strains represents the hallmark of A. baumannii bacteria. We wondered to what extent extensively used strains, so-called reference strains, reflect the dynamic nature and intrinsic heterogeneity of these bacteria. We analyzed multiple phenotypic traits of 43 nonredundant, modern, and multidrug-resistant, extensively drug-resistant, and pandrug-resistant clinical isolates and broadly used strains of A. baumannii. Comparison of these isolates at the genetic and phenotypic levels confirmed a high degree of heterogeneity. Importantly, we observed that a significant portion of modern clinical isolates strongly differs from several historically established strains in the light of colony morphology, cellular density, capsule production, natural transformability, and in vivo virulence. The significant differences between modern clinical isolates of A. baumannii and established strains could hamper the study of A. baumannii, especially concerning its virulence and resistance mechanisms. Hence, we propose a variable collection of modern clinical isolates that are characterized at the genetic and phenotypic levels, covering a wide range of the phenotypic spectrum, with six different macrocolony type groups, from avirulent to hypervirulent phenotypes, and with naturally noncapsulated to hypermucoid strains, with intermediate phenotypes as well. Strain-specific mechanistic observations remain interesting per se, and established "reference" strains have undoubtedly been shown to be very useful to study basic mechanisms of A. baumannii biology. However, any study based on a specific strain of A. baumannii should be compared to modern and clinically relevant isolates. IMPORTANCE Acinetobacter baumannii is a bacterium prioritized by the CDC and WHO because of its increasing antibiotic resistance, leading to treatment failures. The hallmark of this pathogen is the high heterogeneity observed among isolates, due to a very dynamic genome. In this context, we tested if a subset of broadly used isolates, considered "reference" strains, was reflecting the genetic and phenotypic diversity found among currently circulating clinical isolates. We observed that the so-called reference strains do not cover the whole diversity of the modern clinical isolates. While formerly established strains successfully generated a strong base of knowledge in the A. baumannii field and beyond, our study shows that a rational choice of strain, related to a specific biological question, should be taken into consideration. Any data obtained with historically established strains should also be compared to modern and clinically relevant isolates, especially concerning drug screening, resistance, and virulence contexts.
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Affiliation(s)
- Adam Valcek
- Microbial Resistance and Drug Discovery, VIB-VUB Center for Structural Biology, VIB, Flanders Institute for Biotechnology, Brussels, Belgium
- Structural Biology Brussels, Vrije Universiteit Brussel (VUB), Brussels, Belgium
| | - Chantal Philippe
- Research Unit in the Biology of Microorganisms (URBM), NARILIS, University of Namur (UNamur), Namur, Belgium
| | - Clémence Whiteway
- Microbial Resistance and Drug Discovery, VIB-VUB Center for Structural Biology, VIB, Flanders Institute for Biotechnology, Brussels, Belgium
- Structural Biology Brussels, Vrije Universiteit Brussel (VUB), Brussels, Belgium
| | - Etienne Robino
- Microbial Resistance and Drug Discovery, VIB-VUB Center for Structural Biology, VIB, Flanders Institute for Biotechnology, Brussels, Belgium
- Structural Biology Brussels, Vrije Universiteit Brussel (VUB), Brussels, Belgium
| | - Kristina Nesporova
- Microbial Resistance and Drug Discovery, VIB-VUB Center for Structural Biology, VIB, Flanders Institute for Biotechnology, Brussels, Belgium
- Structural Biology Brussels, Vrije Universiteit Brussel (VUB), Brussels, Belgium
| | - Mona Bové
- Laboratory of Pharmaceutical Microbiology, Ghent University, Ghent, Belgium
| | - Tom Coenye
- Laboratory of Pharmaceutical Microbiology, Ghent University, Ghent, Belgium
| | - Tim De Pooter
- Neuromics Support Facility, VIB Center for Molecular Neurology, VIB, Antwerp, Belgium
- Department of Biomedical Sciences, University of Antwerp, Antwerp, Belgium
| | - Wouter De Coster
- Applied and Translational Neurogenomics Group, VIB Center for Molecular Neurology, VIB, Antwerp, Belgium
- Applied and Translational Neurogenomics Group, Department of Biomedical Sciences, University of Antwerp, Antwerp, Belgium
| | - Mojca Strazisar
- Neuromics Support Facility, VIB Center for Molecular Neurology, VIB, Antwerp, Belgium
- Department of Biomedical Sciences, University of Antwerp, Antwerp, Belgium
| | - Charles Van der Henst
- Microbial Resistance and Drug Discovery, VIB-VUB Center for Structural Biology, VIB, Flanders Institute for Biotechnology, Brussels, Belgium
- Structural Biology Brussels, Vrije Universiteit Brussel (VUB), Brussels, Belgium
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7
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Ellison CK, Fei C, Dalia TN, Wingreen NS, Dalia AB, Shaevitz JW, Gitai Z. Subcellular localization of type IV pili regulates bacterial multicellular development. Nat Commun 2022; 13:6334. [PMID: 36284096 PMCID: PMC9596432 DOI: 10.1038/s41467-022-33564-7] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2022] [Accepted: 09/22/2022] [Indexed: 12/25/2022] Open
Abstract
In mammals, subcellular protein localization of factors like planar cell polarity proteins is a key driver of the multicellular organization of tissues. Bacteria also form organized multicellular communities, but these patterns are largely thought to emerge from regulation of whole-cell processes like growth, motility, cell shape, and differentiation. Here we show that a unique intracellular patterning of appendages known as type IV pili (T4P) can drive multicellular development of complex bacterial communities. Specifically, dynamic T4P appendages localize in a line along the long axis of the cell in the bacterium Acinetobacter baylyi. This long-axis localization is regulated by a functionally divergent chemosensory Pil-Chp system, and an atypical T4P protein homologue (FimV) bridges Pil-Chp signaling and T4P positioning. We further demonstrate through modeling and empirical approaches that subcellular T4P localization controls how individual cells interact with one another, independently of T4P dynamics, with different patterns of localization giving rise to distinct multicellular architectures. Our results reveal how subcellular patterning of single cells regulates the development of multicellular bacterial communities.
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Affiliation(s)
- Courtney K. Ellison
- grid.16750.350000 0001 2097 5006Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ USA ,grid.16750.350000 0001 2097 5006Department of Molecular Biology, Princeton University, Princeton, NJ USA ,grid.213876.90000 0004 1936 738XPresent Address: Department of Microbiology, University of Georgia, Athens, GA USA
| | - Chenyi Fei
- grid.16750.350000 0001 2097 5006Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ USA ,grid.16750.350000 0001 2097 5006Department of Molecular Biology, Princeton University, Princeton, NJ USA
| | - Triana N. Dalia
- grid.411377.70000 0001 0790 959XDepartment of Biology, Indiana University, Bloomington, IN USA
| | - Ned S. Wingreen
- grid.16750.350000 0001 2097 5006Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ USA ,grid.16750.350000 0001 2097 5006Department of Molecular Biology, Princeton University, Princeton, NJ USA
| | - Ankur B. Dalia
- grid.411377.70000 0001 0790 959XDepartment of Biology, Indiana University, Bloomington, IN USA
| | - Joshua W. Shaevitz
- grid.16750.350000 0001 2097 5006Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ USA
| | - Zemer Gitai
- grid.16750.350000 0001 2097 5006Department of Molecular Biology, Princeton University, Princeton, NJ USA
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8
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The Impact of Natural Transformation on the Acquisition of Antibiotic Resistance Determinants. mBio 2022; 13:e0033622. [PMID: 35548953 PMCID: PMC9239042 DOI: 10.1128/mbio.00336-22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Carbapenem and multidrug-resistant (MDR) Acinetobacter baumannii leads the World Health Organization's list of priority pathogens and represents an unmet medical need. Understanding the mechanisms underpinning the acquisition of antibiotic resistance in this pathogen is fundamental to the development of novel therapeutics as well as to infection prevention and antibiotic stewardship strategies designed to limit its spread. In their investigation, "Interbacterial Transfer of Carbapenem Resistance and Large Antibiotic Resistance Islands by Natural Transformation in Pathogenic Acinetobacter," Anne-Sophie Godeux and colleagues (mBio 13:e0263121, 2022, https://doi.org/10.1128/mBio.02631-21) delineate the unsuspected extent and circumstances under which natural transformation as a mechanism of intraspecies and interspecies exchange of genetic material occurs in Acinetobacter spp. This study offers key insights into how this notorious pathogen may have accelerated the development of its MDR phenotype via an unexpectedly robust and unnervingly casual approach to the acquisition of antibiotic resistance determinants through natural transformation.
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9
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Whiteway C, Valcek A, Philippe C, Strazisar M, De Pooter T, Mateus I, Breine A, Van der Henst C. Scarless excision of an insertion sequence restores capsule production and virulence in Acinetobacter baumannii. THE ISME JOURNAL 2022; 16:1473-1477. [PMID: 34949784 PMCID: PMC9038732 DOI: 10.1038/s41396-021-01179-3] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/31/2021] [Revised: 12/07/2021] [Accepted: 12/16/2021] [Indexed: 11/12/2022]
Abstract
We identify a new mechanism mediating capsule production and virulence in the WHO and CDC priority ESKAPE pathogen Acinetobacter baumannii. Non-capsulated and avirulent bacteria can revert into a capsulated and virulent state upon scarless excision of an ISAba13 insertion sequence under stress conditions. Reversion events fully restore capsule production and in vivo virulence. This increases our knowledge about A. baumannii genome dynamics, and the regulation of capsule production, virulence and resistance.
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Affiliation(s)
- Clémence Whiteway
- Microbial Resistance and Drug Discovery, VIB-VUB Center for Structural Biology, VIB, Flanders Institute for Biotechnology, Brussels, Belgium.,Structural Biology Brussels, Vrije Universiteit Brussel (VUB), Brussels, Belgium
| | - Adam Valcek
- Microbial Resistance and Drug Discovery, VIB-VUB Center for Structural Biology, VIB, Flanders Institute for Biotechnology, Brussels, Belgium.,Structural Biology Brussels, Vrije Universiteit Brussel (VUB), Brussels, Belgium
| | - Chantal Philippe
- Research Unit in the Biology of Microorganisms (URBM), NARILIS, University of Namur (UNamur), Namur, Belgium
| | - Mojca Strazisar
- Neuromics Support Facility, VIB Center for Molecular Neurology, VIB, Antwerp, Belgium.,Department of Biomedical Sciences, University of Antwerp, Antwerp, Belgium
| | - Tim De Pooter
- Neuromics Support Facility, VIB Center for Molecular Neurology, VIB, Antwerp, Belgium.,Department of Biomedical Sciences, University of Antwerp, Antwerp, Belgium
| | - Ivan Mateus
- Department of Ecology and Evolution, University of Lausanne, Lausanne, Switzerland
| | - Anke Breine
- Microbial Resistance and Drug Discovery, VIB-VUB Center for Structural Biology, VIB, Flanders Institute for Biotechnology, Brussels, Belgium.,Structural Biology Brussels, Vrije Universiteit Brussel (VUB), Brussels, Belgium
| | - Charles Van der Henst
- Microbial Resistance and Drug Discovery, VIB-VUB Center for Structural Biology, VIB, Flanders Institute for Biotechnology, Brussels, Belgium. .,Structural Biology Brussels, Vrije Universiteit Brussel (VUB), Brussels, Belgium.
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10
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Vuillemenot JB, Bour M, Beyrouthy R, Bonnet R, Laaberki MH, Charpentier X, Ruimy R, Plésiat P, Potron A. Genomic analysis of CTX-M-115 and OXA-23/-72 co-producing Acinetobacter baumannii, and their potential to spread resistance genes by natural transformation. J Antimicrob Chemother 2022; 77:1542-1552. [PMID: 35412620 DOI: 10.1093/jac/dkac099] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2021] [Accepted: 02/16/2022] [Indexed: 11/15/2022] Open
Abstract
OBJECTIVES To characterize Acinetobacter baumannii strains co-producing the ESBL CTX-M-115 and carbapenem-hydrolysing class D β-lactamases (CHDLs), and to assess the potential diffusion of their resistance genes by horizontal transfer. METHODS Nineteen CTX-M-115/CHDL-positive A. baumannii were collected between 2015 and 2019 from patients hospitalized in France. Their whole-genome sequences were determined on Illumina and Oxford Nanopore platforms and were compared through core-genome MLST (cgMLST) and SNP analyses. Transferability of resistance genes was investigated by natural transformation assays. RESULTS Eighteen strains were found to harbour CHDL OXA-72, and another one CHDL OXA-23, in addition to CTX-M-115, narrow-spectrum β-lactamases and aminoglycoside resistance determinants including ArmA. cgMLST typing, as well as Oxford Scheme ST and K locus typing, confirmed that 17 out of the 18 CTX-M-115/OXA-72 isolates belonged to new subclades within clonal complex 78 (CC78). The chromosomal region carrying the blaCTX-M-115 gene appeared to vary greatly both in gene content and in length (from 20 to 79 kb) among the strains, likely because of IS26-mediated DNA rearrangements. The blaOXA-72 gene was localized on closely related plasmids showing structural variations that occurred between pdif sites. Transfer of all the β-lactamase genes, as well as aminoglycoside resistance determinants to a drug-susceptible A. baumannii recipient, was easily obtained in vitro by natural transformation. CONCLUSIONS This work highlights the propensity of CC78 isolates to collect multiple antibiotic resistance genes, to rearrange and to pass them to other A. baumannii strains via natural transformation. This process, along with mobile genetic elements, likely contributes to the considerable genomic plasticity of clinical strains, and to the diversity of molecular mechanisms sustaining their multidrug resistance.
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Affiliation(s)
- Jean-Baptiste Vuillemenot
- Centre National de Référence de la Résistance aux Antibiotiques, Centre Hospitalier Universitaire de Besançon, France.,Laboratoire de Bactériologie, UMR 6249 Chrono-Environnement, UFR Santé, Université Bourgogne Franche-Comté, Besançon, France
| | - Maxime Bour
- Centre National de Référence de la Résistance aux Antibiotiques, Centre Hospitalier Universitaire de Besançon, France
| | - Racha Beyrouthy
- UMR INSERM 1071 USC INRA2018, Université Clermont Auvergne, Clermont-Ferrand, France.,Laboratoire associé Centre National de Référence de la Résistance aux Antibiotiques, Centre Hospitalier Universitaire de Clermont-Ferrand, France
| | - Richard Bonnet
- UMR INSERM 1071 USC INRA2018, Université Clermont Auvergne, Clermont-Ferrand, France.,Laboratoire associé Centre National de Référence de la Résistance aux Antibiotiques, Centre Hospitalier Universitaire de Clermont-Ferrand, France
| | - Maria-Halima Laaberki
- CIRI, Centre International de Recherche en Infectiologie, INSERM U1111, Université Claude Bernard Lyon 1, Villeurbanne, France
| | - Xavier Charpentier
- CIRI, Centre International de Recherche en Infectiologie, INSERM U1111, Université Claude Bernard Lyon 1, Villeurbanne, France
| | - Raymond Ruimy
- Laboratoire de Bactériologie, Centre Hospitalier Universitaire de Nice, UMR INSERM C3M, Université Côte d'Azur, Nice, France
| | - Patrick Plésiat
- Centre National de Référence de la Résistance aux Antibiotiques, Centre Hospitalier Universitaire de Besançon, France.,Laboratoire de Bactériologie, UMR 6249 Chrono-Environnement, UFR Santé, Université Bourgogne Franche-Comté, Besançon, France
| | - Anaïs Potron
- Centre National de Référence de la Résistance aux Antibiotiques, Centre Hospitalier Universitaire de Besançon, France.,Laboratoire de Bactériologie, UMR 6249 Chrono-Environnement, UFR Santé, Université Bourgogne Franche-Comté, Besançon, France
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11
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Kirchner L, Averhoff B. DNA binding by pilins and their interaction with the inner membrane platform of the DNA transporter in Thermus thermophilus. BIOCHIMICA ET BIOPHYSICA ACTA. BIOMEMBRANES 2022; 1864:183818. [PMID: 34774498 DOI: 10.1016/j.bbamem.2021.183818] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/10/2021] [Revised: 10/13/2021] [Accepted: 11/05/2021] [Indexed: 06/13/2023]
Abstract
The natural transformation system of Thermus thermophilus has become a model system for studies of the structure and function of DNA transporter in thermophilic bacteria. The DNA transporter in T. thermophilus is functionally linked to type IV pili (T4P) and the major pilin PilA4 plays an essential role in both systems. However, T4P are dispensable for natural transformation. In addition to pilA4, T. thermophilus has a gene cluster encoding the three additional pilins PilA1-PilA3; deletion of the cluster abolished natural transformation but retained T4P biogenesis. In this study, we investigated the roles of single pilins PilA1, PilA2 and PilA3 in natural transformation by mutant studies. These studies revealed that each of these pilins is essential for natural transformation. Two of the pilins, PilA1 and PilA2, were found to bind dsDNA. PilA1 and PilA3 were detected in the inner membrane (IM) but not in the outer membrane (OM) whereas PilA2 was present in both membranes. All three pilins where absent in pilus fractions. This suggests that the pilins form a short DNA binding pseudopilus anchored in the IM. PilA1 was found to bind to the IM assembly platform of the DNA transporter via PilM and PilO. These data are in line with the hypothesis that a DNA binding pseudopilus is connected via an IM platform to the cytosolic motor ATPase PilF.
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Affiliation(s)
- Lennart Kirchner
- Molecular Microbiology & Bioenergetics, Institute of Molecular Biosciences, Johann Wolfgang Goethe University Frankfurt/Main, Max-von-Laue-Str. 9, 60438 Frankfurt, Germany
| | - Beate Averhoff
- Molecular Microbiology & Bioenergetics, Institute of Molecular Biosciences, Johann Wolfgang Goethe University Frankfurt/Main, Max-von-Laue-Str. 9, 60438 Frankfurt, Germany.
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12
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Interbacterial Transfer of Carbapenem Resistance and Large Antibiotic Resistance Islands by Natural Transformation in Pathogenic Acinetobacter. mBio 2022; 13:e0263121. [PMID: 35073754 PMCID: PMC8787482 DOI: 10.1128/mbio.02631-21] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Acinetobacter baumannii infection poses a major health threat, with recurrent treatment failure due to antibiotic resistance, notably to carbapenems. While genomic analyses of clinical strains indicate that homologous recombination plays a major role in the acquisition of antibiotic resistance genes, the underlying mechanisms of horizontal gene transfer often remain speculative. Our understanding of the acquisition of antibiotic resistance is hampered by the lack of experimental systems able to reproduce genomic observations. We here report the detection of recombination events occurring spontaneously in mixed bacterial populations and which can result in the acquisition of resistance to carbapenems. We show that natural transformation is the main driver of intrastrain but also interstrain recombination events between A. baumannii clinical isolates and pathogenic species of Acinetobacter. We observed that interbacterial natural transformation in mixed populations is more efficient at promoting the acquisition of large resistance islands (AbaR4 and AbaR1) than when the same bacteria are supplied with large amounts of purified genomic DNA. Importantly, analysis of the genomes of the recombinant progeny revealed large recombination tracts (from 13 to 123 kb) similar to those observed in the genomes of clinical isolates. Moreover, we highlight that transforming DNA availability is a key determinant of the rate of recombinants and results from both spontaneous release and interbacterial predatory behavior. In the light of our results, natural transformation should be considered a leading mechanism of genome recombination and horizontal gene transfer of antibiotic resistance genes in Acinetobacter baumannii.
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13
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Tickner J, Hawas S, Totsika M, Kenyon JJ. The Wzi outer membrane protein mediates assembly of a tight capsular polysaccharide layer on the Acinetobacter baumannii cell surface. Sci Rep 2021; 11:21741. [PMID: 34741090 PMCID: PMC8571296 DOI: 10.1038/s41598-021-01206-5] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2021] [Accepted: 10/19/2021] [Indexed: 11/30/2022] Open
Abstract
Identification of novel therapeutic targets is required for developing alternate strategies to treat infections caused by the extensively drug-resistant bacterial pathogen, Acinetobacter baumannii. As capsular polysaccharide (CPS) is a prime virulence determinant required for evasion of host immune defenses, understanding the pathways for synthesis and assembly of this discrete cell-surface barrier is important. In this study, we assess cell-bound and cell-free CPS material from A. baumannii AB5075 wildtype and transposon library mutants and demonstrate that the Wzi outer membrane protein is required for the proper assembly of the CPS layer on the cell surface. Loss of Wzi resulted in an estimated 4.4-fold reduction in cell-associated CPS with a reciprocal increase in CPS material shed in the extracellular surrounds. Transmission electron microscopy revealed a disrupted CPS layer with sparse patches of CPS on the external face of the outer membrane when Wzi function was lost. However, this genotype did not have a significant effect on biofilm formation. Genetic analysis demonstrated that the wzi gene is ubiquitous in the species, though the nucleotide sequences were surprisingly diverse. Though divergence was not concomitant with variation at the CPS biosynthesis K locus, an association between wzi type and the first sugar of the CPS representing the base of the structure most likely to interact with Wzi was observed.
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Affiliation(s)
- Jacob Tickner
- grid.1024.70000000089150953Centre of Immunology and Infection Control, School of Biomedical Sciences, Faculty of Health, Queensland University of Technology, Brisbane, Australia
| | - Sophia Hawas
- grid.1024.70000000089150953Centre of Immunology and Infection Control, School of Biomedical Sciences, Faculty of Health, Queensland University of Technology, Brisbane, Australia
| | - Makrina Totsika
- grid.1024.70000000089150953Centre of Immunology and Infection Control, School of Biomedical Sciences, Faculty of Health, Queensland University of Technology, Brisbane, Australia
| | - Johanna J. Kenyon
- grid.1024.70000000089150953Centre of Immunology and Infection Control, School of Biomedical Sciences, Faculty of Health, Queensland University of Technology, Brisbane, Australia
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14
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Winter M, Buckling A, Harms K, Johnsen PJ, Vos M. Antimicrobial resistance acquisition via natural transformation: context is everything. Curr Opin Microbiol 2021; 64:133-138. [PMID: 34710742 DOI: 10.1016/j.mib.2021.09.009] [Citation(s) in RCA: 30] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2021] [Revised: 09/01/2021] [Accepted: 09/23/2021] [Indexed: 10/20/2022]
Abstract
Natural transformation is a process where bacterial cells actively take up free DNA from the environment and recombine it into their genome or reconvert it into extra-chromosomal genetic elements. Although this mechanism is known to mediate the uptake of antibiotic resistance determinants in a range of human pathogens, its importance in the spread of antimicrobial resistance is not always appreciated. This review highlights the context in which transformation takes place: in diverse microbiomes, in interaction with other forms of horizontal gene transfer and in increasingly polluted environments. This examination of the abiotic and biotic drivers of transformation reveals that it could be more important in the dissemination of resistance genes than is often recognised.
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Affiliation(s)
- Macaulay Winter
- European Centre for Environment and Human Health, University of Exeter Medical School, Environment and Sustainability Institute, Penryn Campus, TR10 9FE, United Kingdom
| | - Angus Buckling
- Department of Biosciences, University of Exeter, Penryn Campus, TR10 9FE, United Kingdom
| | - Klaus Harms
- Microbial Pharmacology and Population Biology Research Group, Department of Pharmacy, Faculty of Health Sciences, UiT The Arctic University of Norway, Tromsø, Norway
| | - Pål Jarle Johnsen
- Microbial Pharmacology and Population Biology Research Group, Department of Pharmacy, Faculty of Health Sciences, UiT The Arctic University of Norway, Tromsø, Norway
| | - Michiel Vos
- European Centre for Environment and Human Health, University of Exeter Medical School, Environment and Sustainability Institute, Penryn Campus, TR10 9FE, United Kingdom.
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15
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Environmental Free-Living Amoebae Can Predate on Diverse Antibiotic-Resistant Human Pathogens. Appl Environ Microbiol 2021; 87:e0074721. [PMID: 34232736 PMCID: PMC8388808 DOI: 10.1128/aem.00747-21] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Here, we sought to test the resistance of human pathogens to unaltered environmental free-living amoebae. Amoebae are ubiquitous eukaryotic microorganisms and important predators of bacteria. Environmental amoebae have also been proposed to serve as both potential reservoirs and training grounds for human pathogens. However, studies addressing their relationships with human pathogens often rely on a few domesticated amoebae that have been selected to feed on rich medium, thereby possibly overestimating the resistance of pathogens to these predatory phagocytes. From an open-air composting site, we recovered over 100 diverse amoebae that were able to feed on Acinetobacter baumannii and Klebsiella pneumoniae. In a standardized and quantitative assay for predation, the isolated amoebae showed a broad predation spectrum, killing clinical isolates of A. baumannii, K. pneumoniae, Pseudomonas aeruginosa, and Staphylococcus aureus. Interestingly, A. baumannii, which was previously reported to resist predation by laboratory strains of Acanthamoeba, was efficiently consumed by closely related environmental amoebae. The isolated amoebae were capable of feeding on highly virulent carbapenem-resistant or methicillin-resistant clinical isolates. In conclusion, the natural environment is a rich source of amoebae with broad-spectrum bactericidal activities, including against antibiotic-resistant isolates. IMPORTANCE Free-living amoebae have been proposed to play an important role in hosting and disseminating various human pathogens. The resistance of human pathogens to predation by amoebae is often derived from in vitro experiments using model amoebae. Here, we sought to isolate environmental amoebae and to test their predation on diverse human pathogens, with results that challenge conclusions based on model amoebae. We found that the natural environment is a rich source of diverse amoebae with broad-spectrum predatory activities against human pathogens, including highly virulent and antibiotic-resistant clinical isolates.
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16
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Acinetobacter baylyi regulates type IV pilus synthesis by employing two extension motors and a motor protein inhibitor. Nat Commun 2021; 12:3744. [PMID: 34145281 PMCID: PMC8213720 DOI: 10.1038/s41467-021-24124-6] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2021] [Accepted: 06/02/2021] [Indexed: 11/08/2022] Open
Abstract
Bacteria use extracellular appendages called type IV pili (T4P) for diverse behaviors including DNA uptake, surface sensing, virulence, protein secretion, and twitching motility. Dynamic extension and retraction of T4P is essential for their function, and T4P extension is thought to occur through the action of a single, highly conserved motor, PilB. Here, we develop Acinetobacter baylyi as a model to study T4P by employing a recently developed pilus labeling method. By contrast to previous studies of other bacterial species, we find that T4P synthesis in A. baylyi is dependent not only on PilB but also on an additional, phylogenetically distinct motor, TfpB. Furthermore, we identify a protein (CpiA) that inhibits T4P extension by specifically binding and inhibiting PilB but not TfpB. These results expand our understanding of T4P regulation and highlight how inhibitors might be exploited to disrupt T4P synthesis. Type IV pili (T4P) are retractile appendages used by bacteria for DNA uptake and other purposes. T4P extension is thought to occur through the action of a single motor protein, PilB. Here, Ellison et al. show that T4P synthesis in Acinetobacter baylyi depends not only on PilB but also on an additional, distinct motor, TfpB.
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17
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Pilus Production in Acinetobacter baumannii Is Growth Phase Dependent and Essential for Natural Transformation. J Bacteriol 2021; 203:JB.00034-21. [PMID: 33495250 PMCID: PMC8088505 DOI: 10.1128/jb.00034-21] [Citation(s) in RCA: 29] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2021] [Accepted: 01/19/2021] [Indexed: 12/17/2022] Open
Abstract
Rapid bacterial evolution has alarming negative impacts on animal and human health which can occur when pathogens acquire antimicrobial resistance traits. As a major cause of antibiotic-resistant opportunistic infections, A. baumannii is a high-priority health threat which has motivated renewed interest in studying how this pathogen acquires new, dangerous traits. Acinetobacter baumannii is a severe threat to human health as a frequently multidrug-resistant hospital-acquired pathogen. Part of the danger from this bacterium comes from its genome plasticity and ability to evolve quickly by taking up and recombining external DNA into its own genome in a process called natural competence for transformation. This mode of horizontal gene transfer is one of the major ways that bacteria can acquire new antimicrobial resistances and toxic traits. Because these processes in A. baumannii are not well studied, we herein characterized new aspects of natural transformability in this species that include the species’ competence window. We uncovered a strong correlation with a growth phase-dependent synthesis of a type IV pilus (TFP), which constitutes the central part of competence-induced DNA uptake machinery. We used bacterial genetics and microscopy to demonstrate that the TFP is essential for the natural transformability and surface motility of A. baumannii, whereas pilus-unrelated proteins of the DNA uptake complex do not affect the motility phenotype. Furthermore, TFP biogenesis and assembly is subject to input from two regulatory systems that are homologous to Pseudomonas aeruginosa, namely, the PilSR two-component system and the Pil-Chp chemosensory system. We demonstrated that these systems affect not only the piliation status of cells but also their ability to take up DNA for transformation. Importantly, we report on discrepancies between TFP biogenesis and natural transformability within the same genus by comparing data for our work on A. baumannii to data reported for Acinetobacter baylyi, the latter of which served for decades as a model for natural competence. IMPORTANCE Rapid bacterial evolution has alarming negative impacts on animal and human health which can occur when pathogens acquire antimicrobial resistance traits. As a major cause of antibiotic-resistant opportunistic infections, A. baumannii is a high-priority health threat which has motivated renewed interest in studying how this pathogen acquires new, dangerous traits. In this study, we deciphered a specific time window in which these bacteria can acquire new DNA and correlated that with its ability to produce the external appendages that contribute to the DNA acquisition process. These cell appendages function doubly for motility on surfaces and for DNA uptake. Collectively, we showed that A. baumannii is similar in its TFP production to Pseudomonas aeruginosa, though it differs from the well-studied species A. baylyi.
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18
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Blaschke U, Skiebe E, Wilharm G. Novel Genes Required for Surface-Associated Motility in Acinetobacter baumannii. Curr Microbiol 2021; 78:1509-1528. [PMID: 33666749 PMCID: PMC7997844 DOI: 10.1007/s00284-021-02407-x] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2020] [Accepted: 02/10/2021] [Indexed: 01/28/2023]
Abstract
Acinetobacter baumannii is an opportunistic and increasingly multi-drug resistant human pathogen rated as a critical priority one pathogen for the development of new antibiotics by the WHO in 2017. Despite the lack of flagella, A. baumannii can move along wet surfaces in two different ways: via twitching motility and surface-associated motility. While twitching motility is known to depend on type IV pili, the mechanism of surface-associated motility is poorly understood. In this study, we established a library of 30 A. baumannii ATCC® 17978™ mutants that displayed deficiency in surface-associated motility. By making use of natural competence, we also introduced these mutations into strain 29D2 to differentiate strain-specific versus species-specific effects of mutations. Mutated genes were associated with purine/pyrimidine/folate biosynthesis (e.g. purH, purF, purM, purE), alarmone/stress metabolism (e.g. Ap4A hydrolase), RNA modification/regulation (e.g. methionyl-tRNA synthetase), outer membrane proteins (e.g. ompA), and genes involved in natural competence (comEC). All tested mutants originally identified as motility-deficient in strain ATCC® 17978™ also displayed a motility-deficient phenotype in 29D2. By contrast, further comparative characterization of the mutant sets of both strains regarding pellicle biofilm formation, antibiotic resistance, and virulence in the Galleria mellonella infection model revealed numerous strain-specific mutant phenotypes. Our studies highlight the need for comparative analyses to characterize gene functions in A. baumannii and for further studies on the mechanisms underlying surface-associated motility.
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Affiliation(s)
- Ulrike Blaschke
- Robert Koch Institute, Project group P2, Burgstr. 37, 38855, Wernigerode, Germany.
| | - Evelyn Skiebe
- Robert Koch Institute, Project group P2, Burgstr. 37, 38855, Wernigerode, Germany
| | - Gottfried Wilharm
- Robert Koch Institute, Project group P2, Burgstr. 37, 38855, Wernigerode, Germany.
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19
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Osman M, B Halimeh F, Rafei R, Mallat H, Tom JE, Raad EB, M Diene S, Jamal S, Atrouni AA, Dabboussi F, Moudani W, Madec JY, Saras E, Lupo A, Haenni M, Rolain JM, Hamze M. Investigation of an XDR-Acinetobacter baumannii ST2 outbreak in an intensive care unit of a Lebanese tertiary care hospital. Future Microbiol 2020; 15:1535-1542. [DOI: 10.2217/fmb-2020-0079] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
Aim: We sought to investigate the genetic epidemiological relatedness of carbapenem-resistant Acinetobacter baumannii (CRAB) strains of a suspected outbreak in a Lebanese tertiary care hospital to implement necessary infection prevention and control measures. Methods: Twenty-eight nonduplicate CRAB isolates detected among hospitalized patients between January 2016 and July 2017 were studied by real-time polymerase chain reaction (PCR), pulsed-field gel electrophoresis and multilocus sequence typing analyses. Results: Twenty-seven isolates harbored blaOXA-23, of which one also carried blaNDM-1. The isolates distributed temporally in two presumably episodes were stratified by pulsed-field gel electrophoresis into many clusters. Although several clones have become endemic in the hospital, we have rapidly implemented appropriate infection prevention and control measures, achieving full eradication from August 2017 to November 2019. Conclusion: We have successfully investigated and controlled a polyclonal outbreak of OXA-23 producing ST2 CRAB.
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Affiliation(s)
- Marwan Osman
- Laboratoire Microbiologie Santé et Environnement (LMSE), Doctoral School of Science & Technology, Faculty of Public Health, Lebanese University, Tripoli, Lebanon
| | - Fatima B Halimeh
- Laboratoire Microbiologie Santé et Environnement (LMSE), Doctoral School of Science & Technology, Faculty of Public Health, Lebanese University, Tripoli, Lebanon
- Aix-Marseille University, IRD, APHM, MEPHI, IHU Méditerranée infection, Faculté de Médecine et de Pharmacie, 19-21 boulevard Jean Moulin, 13385 Marseille CEDEX 05, France
| | - Rayane Rafei
- Laboratoire Microbiologie Santé et Environnement (LMSE), Doctoral School of Science & Technology, Faculty of Public Health, Lebanese University, Tripoli, Lebanon
| | - Hassan Mallat
- Laboratoire Microbiologie Santé et Environnement (LMSE), Doctoral School of Science & Technology, Faculty of Public Health, Lebanese University, Tripoli, Lebanon
- El Youssef Hospital Center, Halba, Lebanon
| | - Jad El Tom
- El Youssef Hospital Center, Halba, Lebanon
| | | | - Seydina M Diene
- Aix-Marseille University, IRD, APHM, MEPHI, IHU Méditerranée infection, Faculté de Médecine et de Pharmacie, 19-21 boulevard Jean Moulin, 13385 Marseille CEDEX 05, France
| | - Sabah Jamal
- Laboratoire Microbiologie Santé et Environnement (LMSE), Doctoral School of Science & Technology, Faculty of Public Health, Lebanese University, Tripoli, Lebanon
| | - Ahmad Al Atrouni
- Laboratoire Microbiologie Santé et Environnement (LMSE), Doctoral School of Science & Technology, Faculty of Public Health, Lebanese University, Tripoli, Lebanon
| | - Fouad Dabboussi
- Laboratoire Microbiologie Santé et Environnement (LMSE), Doctoral School of Science & Technology, Faculty of Public Health, Lebanese University, Tripoli, Lebanon
| | - Walid Moudani
- Laboratoire Microbiologie Santé et Environnement (LMSE), Doctoral School of Science & Technology, Faculty of Public Health, Lebanese University, Tripoli, Lebanon
| | - Jean-Yves Madec
- Université de Lyon – ANSES laboratoire de Lyon, Unité Antibiorésistance et Virulence Bactériennes, France
| | - Estelle Saras
- Université de Lyon – ANSES laboratoire de Lyon, Unité Antibiorésistance et Virulence Bactériennes, France
| | - Agnese Lupo
- Université de Lyon – ANSES laboratoire de Lyon, Unité Antibiorésistance et Virulence Bactériennes, France
| | - Marisa Haenni
- Université de Lyon – ANSES laboratoire de Lyon, Unité Antibiorésistance et Virulence Bactériennes, France
| | - Jean-Marc Rolain
- Aix-Marseille University, IRD, APHM, MEPHI, IHU Méditerranée infection, Faculté de Médecine et de Pharmacie, 19-21 boulevard Jean Moulin, 13385 Marseille CEDEX 05, France
| | - Monzer Hamze
- Laboratoire Microbiologie Santé et Environnement (LMSE), Doctoral School of Science & Technology, Faculty of Public Health, Lebanese University, Tripoli, Lebanon
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20
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Kurushima J, Campo N, van Raaphorst R, Cerckel G, Polard P, Veening JW. Unbiased homeologous recombination during pneumococcal transformation allows for multiple chromosomal integration events. eLife 2020; 9:e58771. [PMID: 32965219 PMCID: PMC7567608 DOI: 10.7554/elife.58771] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2020] [Accepted: 09/22/2020] [Indexed: 01/25/2023] Open
Abstract
The spread of antimicrobial resistance and vaccine escape in the human pathogen Streptococcus pneumoniae can be largely attributed to competence-induced transformation. Here, we studied this process at the single-cell level. We show that within isogenic populations, all cells become naturally competent and bind exogenous DNA. We find that transformation is highly efficient and that the chromosomal location of the integration site or whether the transformed gene is encoded on the leading or lagging strand has limited influence on recombination efficiency. Indeed, we have observed multiple recombination events in single recipients in real-time. However, because of saturation and because a single-stranded donor DNA replaces the original allele, transformation efficiency has an upper threshold of approximately 50% of the population. The fixed mechanism of transformation results in a fail-safe strategy for the population as half of the population generally keeps an intact copy of the original genome.
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Affiliation(s)
- Jun Kurushima
- Department of Fundamental Microbiology, Faculty of Biology and Medicine, University of LausanneLausanneSwitzerland
| | - Nathalie Campo
- Laboratoire de Microbiologie et Génétique Moléculaires (LMGM), Centre de Biologie Intégrative (CBI)ToulouseFrance
| | - Renske van Raaphorst
- Department of Fundamental Microbiology, Faculty of Biology and Medicine, University of LausanneLausanneSwitzerland
| | - Guillaume Cerckel
- Department of Fundamental Microbiology, Faculty of Biology and Medicine, University of LausanneLausanneSwitzerland
| | - Patrice Polard
- Laboratoire de Microbiologie et Génétique Moléculaires (LMGM), Centre de Biologie Intégrative (CBI)ToulouseFrance
| | - Jan-Willem Veening
- Department of Fundamental Microbiology, Faculty of Biology and Medicine, University of LausanneLausanneSwitzerland
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21
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Scarless Removal of Large Resistance Island AbaR Results in Antibiotic Susceptibility and Increased Natural Transformability in Acinetobacter baumannii. Antimicrob Agents Chemother 2020; 64:AAC.00951-20. [PMID: 32778544 PMCID: PMC7508600 DOI: 10.1128/aac.00951-20] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2020] [Accepted: 07/27/2020] [Indexed: 01/07/2023] Open
Abstract
With a great diversity in gene composition, including multiple putative antibiotic resistance genes, AbaR islands are potential contributors to multidrug resistance in Acinetobacter baumannii. However, the effective contribution of AbaR to antibiotic resistance and bacterial physiology remains elusive. To address this, we sought to accurately remove AbaR islands and restore the integrity of their insertion site. To this end, we devised a versatile scarless genome editing strategy. With a great diversity in gene composition, including multiple putative antibiotic resistance genes, AbaR islands are potential contributors to multidrug resistance in Acinetobacter baumannii. However, the effective contribution of AbaR to antibiotic resistance and bacterial physiology remains elusive. To address this, we sought to accurately remove AbaR islands and restore the integrity of their insertion site. To this end, we devised a versatile scarless genome editing strategy. We performed this genetic modification in two recent A. baumannii clinical strains: the strain AB5075 and the nosocomial strain AYE, which carry AbaR11 and AbaR1 islands of 19.7 kbp and 86.2 kbp, respectively. Antibiotic susceptibilities were then compared between the parental strains and their AbaR-cured derivatives. As anticipated by the predicted function of the open reading frame (ORF) of this island, the antibiotic resistance profiles were identical between the wild type and the AbaR11-cured AB5075 strains. In contrast, AbaR1 carries 25 ORFs, with predicted resistance to several classes of antibiotics, and the AYE AbaR1-cured derivative showed restored susceptibility to multiple classes of antibiotics. Moreover, curing of AbaRs restored high levels of natural transformability. Indeed, most AbaR islands are inserted into the comM gene involved in natural transformation. Our data indicate that AbaR insertion effectively inactivates comM and that the restored comM is functional. Curing of AbaR consistently resulted in highly transformable and therefore easily genetically tractable strains. Emendation of AbaR provides insight into the functional consequences of AbaR acquisition.
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22
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Carvalho G, Fouchet D, Danesh G, Godeux AS, Laaberki MH, Pontier D, Charpentier X, Venner S. Bacterial Transformation Buffers Environmental Fluctuations through the Reversible Integration of Mobile Genetic Elements. mBio 2020; 11:mBio.02443-19. [PMID: 32127449 PMCID: PMC7064763 DOI: 10.1128/mbio.02443-19] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Horizontal gene transfer (HGT) promotes the spread of genes within bacterial communities. Among the HGT mechanisms, natural transformation stands out as being encoded by the bacterial core genome. Natural transformation is often viewed as a way to acquire new genes and to generate genetic mixing within bacterial populations. Another recently proposed function is the curing of bacterial genomes of their infectious parasitic mobile genetic elements (MGEs). Here, we propose that these seemingly opposing theoretical points of view can be unified. Although costly for bacterial cells, MGEs can carry functions that are at points in time beneficial to bacteria under stressful conditions (e.g., antibiotic resistance genes). Using computational modeling, we show that, in stochastic environments, an intermediate transformation rate maximizes bacterial fitness by allowing the reversible integration of MGEs carrying resistance genes, although these MGEs are costly for host cell replication. Based on this dual function (MGE acquisition and removal), transformation would be a key mechanism for stabilizing the bacterial genome in the long term, and this would explain its striking conservation.IMPORTANCE Natural transformation is the acquisition, controlled by bacteria, of extracellular DNA and is one of the most common mechanisms of horizontal gene transfer, promoting the spread of resistance genes. However, its evolutionary function remains elusive, and two main roles have been proposed: (i) the new gene acquisition and genetic mixing within bacterial populations and (ii) the removal of infectious parasitic mobile genetic elements (MGEs). While the first one promotes genetic diversification, the other one promotes the removal of foreign DNA and thus genome stability, making these two functions apparently antagonistic. Using a computational model, we show that intermediate transformation rates, commonly observed in bacteria, allow the acquisition then removal of MGEs. The transient acquisition of costly MGEs with resistance genes maximizes bacterial fitness in environments with stochastic stress exposure. Thus, transformation would ensure both a strong dynamic of the bacterial genome in the short term and its long-term stabilization.
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Affiliation(s)
- Gabriel Carvalho
- Université de Lyon, Université Lyon 1, CNRS, Laboratoire de Biométrie et Biologie Evolutive UMR 5558, Villeurbanne, France
| | - David Fouchet
- Université de Lyon, Université Lyon 1, CNRS, Laboratoire de Biométrie et Biologie Evolutive UMR 5558, Villeurbanne, France
| | - Gonché Danesh
- Université de Lyon, Université Lyon 1, CNRS, Laboratoire de Biométrie et Biologie Evolutive UMR 5558, Villeurbanne, France
| | - Anne-Sophie Godeux
- CIRI, Centre International de Recherche en Infectiologie, Inserm, U1111, Université Claude Bernard Lyon 1, Villeurbanne, France
- CNRS UMR5308, École Normale Supérieure de Lyon, University of Lyon, Villeurbanne, France
| | - Maria-Halima Laaberki
- CIRI, Centre International de Recherche en Infectiologie, Inserm, U1111, Université Claude Bernard Lyon 1, Villeurbanne, France
- Université de Lyon, VetAgro Sup, Marcy-l'Étoile, France
- CNRS UMR5308, École Normale Supérieure de Lyon, University of Lyon, Villeurbanne, France
| | - Dominique Pontier
- Université de Lyon, Université Lyon 1, CNRS, Laboratoire de Biométrie et Biologie Evolutive UMR 5558, Villeurbanne, France
| | - Xavier Charpentier
- CIRI, Centre International de Recherche en Infectiologie, Inserm, U1111, Université Claude Bernard Lyon 1, Villeurbanne, France
- CNRS UMR5308, École Normale Supérieure de Lyon, University of Lyon, Villeurbanne, France
| | - Samuel Venner
- Université de Lyon, Université Lyon 1, CNRS, Laboratoire de Biométrie et Biologie Evolutive UMR 5558, Villeurbanne, France
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23
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Hu Y, He L, Tao X, Meng F, Zhang J. High DNA Uptake Capacity of International Clone II Acinetobacter baumannii Detected by a Novel Planktonic Natural Transformation Assay. Front Microbiol 2019; 10:2165. [PMID: 31616393 PMCID: PMC6768954 DOI: 10.3389/fmicb.2019.02165] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2019] [Accepted: 09/03/2019] [Indexed: 12/21/2022] Open
Abstract
Acquisition of novel resistance genes is a key driver of multidrug resistance in the nosocomial pathogen Acinetobacter baumannii. To investigate the DNA uptake ability among clinical A. baumannii strains, a planktonic salt-free transformation assay was developed. A total of 142 clinical A. baumannii isolates with divergent genetic distance were selected, and 86 of them belong to international clonal lineage II (ICL2). Using this new transformation assay, 38% of the clinical A. baumannii isolates were natural competent. Among the multidrug-resistant (MDR) isolates, the transformable isolates all belonging to the ICLs, and showed significant higher transformation frequency compared with sensitive isolates. In addition, some of the ICL2 isolates triggered competence much earlier than the sensitive isolates with similar transformation frequencies. This may give them more opportunities to obtain successful transformation in their natural environment and provides an important clue to explain the severe drug resistance and clinical successfulness of ICL2.
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Affiliation(s)
- Yuan Hu
- State Key Laboratory of Infectious Disease Prevention and Control, Collaborative Innovation Center for Diagnosis and Treatment of Infectious Diseases, National Institute for Communicable Disease Control and Prevention, Chinese Center for Disease Control and Prevention, Beijing, China
| | - Lihua He
- State Key Laboratory of Infectious Disease Prevention and Control, Collaborative Innovation Center for Diagnosis and Treatment of Infectious Diseases, National Institute for Communicable Disease Control and Prevention, Chinese Center for Disease Control and Prevention, Beijing, China
| | - Xiaoxia Tao
- State Key Laboratory of Infectious Disease Prevention and Control, Collaborative Innovation Center for Diagnosis and Treatment of Infectious Diseases, National Institute for Communicable Disease Control and Prevention, Chinese Center for Disease Control and Prevention, Beijing, China
| | - Fanliang Meng
- State Key Laboratory of Infectious Disease Prevention and Control, Collaborative Innovation Center for Diagnosis and Treatment of Infectious Diseases, National Institute for Communicable Disease Control and Prevention, Chinese Center for Disease Control and Prevention, Beijing, China
| | - Jianzhong Zhang
- State Key Laboratory of Infectious Disease Prevention and Control, Collaborative Innovation Center for Diagnosis and Treatment of Infectious Diseases, National Institute for Communicable Disease Control and Prevention, Chinese Center for Disease Control and Prevention, Beijing, China
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24
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Abstract
Natural transformation is a major mechanism of horizontal gene transfer. Although the genes required for natural transformation are nearly ubiquitous in bacteria, it is commonly reported that some isolates of transformable species fail to transform. In Legionella pneumophila, we show that the inability of multiple clinical isolates to transform is caused by a conjugative element that shuts down expression of genes required for transformation. Diverse conjugative elements in the Legionella genus have adopted the same inhibition strategy. We propose that inhibition of natural transformation by episomal and integrated conjugative elements can explain the lack of transformability of isolates and also the apparent lack of natural transformation in some species. Natural transformation (i.e., the uptake of DNA and its stable integration in the chromosome) is a major mechanism of horizontal gene transfer in bacteria. Although the vast majority of bacterial genomes carry the genes involved in natural transformation, close relatives of naturally transformable species often appear not competent for natural transformation. In addition, unexplained extensive variations in the natural transformation phenotype have been reported in several species. Here, we addressed this phenomenon by conducting a genome-wide association study (GWAS) on a panel of isolates of the opportunistic pathogen Legionella pneumophila. GWAS revealed that the absence of the transformation phenotype is associated with the conjugative plasmid pLPL. The plasmid inhibits transformation by simultaneously silencing the genes required for DNA uptake and recombination. We identified a small RNA (sRNA), RocRp, as the sole plasmid-encoded factor responsible for the silencing of natural transformation. RocRp is homologous to the highly conserved and chromosome-encoded sRNA RocR which controls the transient expression of the DNA uptake system. Assisted by the ProQ/FinO-domain RNA chaperone RocC, RocRp acts as a substitute of RocR, ensuring that the bacterial host of the conjugative plasmid does not become naturally transformable. Distinct homologs of this plasmid-encoded sRNA are found in diverse conjugative elements in other Legionella species. Their low to high prevalence may result in the lack of transformability of some isolates up to the apparent absence of natural transformation in the species. Generally, our work suggests that conjugative elements obscure the widespread occurrence of natural transformability in bacteria.
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25
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Competence for Natural Transformation Is Common among Clinical Strains of Resistant Acinetobacter spp. Microorganisms 2019; 7:microorganisms7020030. [PMID: 30682786 PMCID: PMC6406254 DOI: 10.3390/microorganisms7020030] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2018] [Revised: 01/11/2019] [Accepted: 01/22/2019] [Indexed: 11/17/2022] Open
Abstract
Horizontal gene transfer events provide the basis for extensive dissemination of antimicrobial resistance traits between bacterial populations. Conjugation is considered to be the most frequent mechanism behind new resistance acquisitions in clinical pathogens but does not fully explain the resistance patterns seen in some bacterial genera. Gene transfer by natural transformation has been described for numerous clinical isolates, including some Acinetobacter species. The main aim of this study was to determine to what extent clinical, resistant Acinetobacter spp. isolates, express competence for natural transformation. Twenty-two clinical Acinetobacter spp. isolates collected over a 16-year time period, from five different geographical separated and/or distinct Portuguese Hospitals were tested for natural transformability. Fourteen isolates, including 11 A. baumannii, 2 A. nosocomialis and 1 Acinetobacter sp., were identified as competent on semisolid media facilitating surface-motility. Competent Acinetobacter isolates were found in all the hospitals tested. Furthermore, osmolarity was shown to influence the uptake of exogenous DNA by competent A. baumannii A118. Our study demonstrates that natural competence is common among clinical isolates of Acinetobacter spp., and hence likely an important trait for resistance acquisition.
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