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Harmer CJ, Hall RM. IS 26 and the IS 26 family: versatile resistance gene movers and genome reorganizers. Microbiol Mol Biol Rev 2024; 88:e0011922. [PMID: 38436262 PMCID: PMC11332343 DOI: 10.1128/mmbr.00119-22] [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] [Indexed: 03/05/2024] Open
Abstract
SUMMARYIn Gram-negative bacteria, the insertion sequence IS26 is highly active in disseminating antibiotic resistance genes. IS26 can recruit a gene or group of genes into the mobile gene pool and support their continued dissemination to new locations by creating pseudo-compound transposons (PCTs) that can be further mobilized by the insertion sequence (IS). IS26 can also enhance expression of adjacent potential resistance genes. IS26 encodes a DDE transposase but has unique properties. It forms cointegrates between two separate DNA molecules using two mechanisms. The well-known copy-in (replicative) route generates an additional IS copy and duplicates the target site. The recently discovered and more efficient and targeted conservative mechanism requires an IS in both participating molecules and does not generate any new sequence. The unit of movement for PCTs, known as a translocatable unit or TU, includes only one IS26. TU formed by homologous recombination between the bounding IS26s can be reincorporated via either cointegration route. However, the targeted conservative reaction is key to generation of arrays of overlapping PCTs seen in resistant pathogens. Using the copy-in route, IS26 can also act on a site in the same DNA molecule, either inverting adjacent DNA or generating an adjacent deletion plus a circular molecule carrying the DNA segment lost and an IS copy. If reincorporated, these circular molecules create a new PCT. IS26 is the best characterized IS in the IS26 family, which includes IS257/IS431, ISSau10, IS1216, IS1006, and IS1008 that are also implicated in spreading resistance genes in Gram-positive and Gram-negative pathogens.
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Affiliation(s)
- Christopher J. Harmer
- School of Life and Environmental Sciences, The University of Sydney, Sydney, New South Wales, Australia
| | - Ruth M. Hall
- School of Life and Environmental Sciences, The University of Sydney, Sydney, New South Wales, Australia
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Wang Y, Dagan T. The evolution of antibiotic resistance islands occurs within the framework of plasmid lineages. Nat Commun 2024; 15:4555. [PMID: 38811529 PMCID: PMC11137137 DOI: 10.1038/s41467-024-48352-8] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2023] [Accepted: 04/25/2024] [Indexed: 05/31/2024] Open
Abstract
Bacterial pathogens carrying multidrug resistance (MDR) plasmids are a major threat to human health. The acquisition of antibiotic resistance genes (ARGs) in plasmids is often facilitated by mobile genetic elements that copy or translocate ARGs between DNA molecules. The agglomeration of mobile elements in plasmids generates resistance islands comprising multiple ARGs. However, whether the emergence of resistance islands is restricted to specific MDR plasmid lineages remains understudied. Here we show that the agglomeration of ARGs in resistance islands is biased towards specific large plasmid lineages. Analyzing 6784 plasmids in 2441 Escherichia, Salmonella, and Klebsiella isolates, we quantify that 84% of the ARGs in MDR plasmids are found in resistance islands. We furthermore observe rapid evolution of ARG combinations in resistance islands. Most regions identified as resistance islands are shared among closely related plasmids but rarely among distantly related plasmids. Our results suggest the presence of barriers for the dissemination of ARGs between plasmid lineages, which are related to plasmid genetic properties, host range and the plasmid evolutionary history. The agglomeration of ARGs in plasmids is attributed to the workings of mobile genetic elements that operate within the framework of existing plasmid lineages.
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Affiliation(s)
- Yiqing Wang
- Institute of General Microbiology, Kiel University, Kiel, Germany
| | - Tal Dagan
- Institute of General Microbiology, Kiel University, Kiel, Germany.
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Harmer CJ, Lebreton F, Stam J, McGann PT, Hall RM. Mechanisms of IS 26-Mediated Amplification of the aphA1 Gene Leading to Tobramycin Resistance in an Acinetobacter baumannii Isolate. Microbiol Spectr 2022; 10:e0228722. [PMID: 36073931 PMCID: PMC9602291 DOI: 10.1128/spectrum.02287-22] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2022] [Accepted: 08/19/2022] [Indexed: 01/04/2023] Open
Abstract
Enhanced levels of resistance to antibiotics arising from amplification of an antibiotic resistance gene that impact therapeutic options are increasingly observed. Amplification can also disclose novel phenotypes leading to treatment failure. However, the mechanism is poorly understood. Here, the route to amplification of the aphA1 kanamycin and neomycin resistance gene during tobramycin treatment of an Acinetobacter baumannii clinical isolate, leading to tobramycin resistance and treatment failure, was investigated. In the tobramycin-susceptible parent isolate, MRSN56, a single copy of aphA1 is present in the pseudocompound transposon PTn6020, bounded by directly oriented copies of IS26. For two clinical resistant isolates, new long-read sequence data were combined with available short-read data to complete the genomes. Comparison to the completed genome of MRSN56 revealed that, in both cases, IS26 had generated a circular translocatable unit (TU) containing PTn6020 and additional adjacent DNA. In one case, this TU was reincorporated into the second product generated by the deletion that formed the TU via the targeted conservative route and amplified about 7 times. In the second case, the TU was incorporated at a new location via the copy-in route and amplified about 65 times. Experimental amplification ex vivo by subjecting MRSN56 to tobramycin selection pressure yielded different TUs, which were incorporated at either the original location or a new location and amplified many times. The outcomes suggest that when IS26 is involved, amplification occurs via rolling circle replication of a newly formed TU coupled to the IS26-mediated TU formation or reincorporation step. IMPORTANCE Heteroresistance, a significant issue that is known to impact antibiotic treatment outcomes, is caused by the presence of spontaneously arising cells with elevated levels of resistance to therapeutically important antibiotics in a population of susceptible cells. Gene amplification is one well-documented cause of heteroresistance, but precisely how extensive amplification occurs is not understood. Here, we establish the case for the direct involvement of IS26 activity in the amplification of the aphA1 gene to disclose resistance to tobramycin. The aphA1 gene is usually found associated with IS26 in Gram-negative pathogens and is commonly found in extensively resistant Acinetobacter baumannii strains. IS26 and related IS cause adjacent deletions, forming a nonreplicating circular molecule known as a translocatable unit (TU), and amplification via a rolling circle mechanism appears to be coupled to either IS26-mediated TU formation or reincorporation. Related IS found in Gram-positive pathogens may play a similar role.
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Affiliation(s)
- Christopher J. Harmer
- School of Life and Environmental Sciences, The University of Sydney, Sydney, New South Wales, Australia
| | - Francois Lebreton
- Multidrug Resistant Organism Repository and Surveillance Network, Walter Reed Army Institute of Research, Silver Spring, Maryland, USA
| | - Jason Stam
- Multidrug Resistant Organism Repository and Surveillance Network, Walter Reed Army Institute of Research, Silver Spring, Maryland, USA
| | - Patrick T. McGann
- Multidrug Resistant Organism Repository and Surveillance Network, Walter Reed Army Institute of Research, Silver Spring, Maryland, USA
| | - Ruth M. Hall
- School of Life and Environmental Sciences, The University of Sydney, Sydney, New South Wales, Australia
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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: 5] [Impact Index Per Article: 2.5] [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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Jones NI, Harmer CJ, Hamidian M, Hall RM. Evolution of Acinetobacter baumannii plasmids carrying the oxa58 carbapenemase resistance gene via plasmid fusion, IS26-mediated events and dif module shuffling. Plasmid 2022; 121:102628. [DOI: 10.1016/j.plasmid.2022.102628] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2021] [Revised: 03/03/2022] [Accepted: 03/07/2022] [Indexed: 10/18/2022]
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