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Harmer CJ, Nelson MJ, Lebreton F, Lertsethtakarn P, McGann PT, Hall RM. Distribution and expression of the aac(6')-Im (aacA16) aminoglycoside resistance gene. J Antimicrob Chemother 2024; 79:1569-1576. [PMID: 38742708 PMCID: PMC11215538 DOI: 10.1093/jac/dkae136] [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: 02/12/2024] [Accepted: 04/22/2024] [Indexed: 05/16/2024] Open
Abstract
BACKGROUND The aac(6')-Im (aacA16) amikacin, netilmicin and tobramycin resistance gene cassette had been circulating globally undetected for many years in a sublineage of Acinetobacter baumannii global clone 2. OBJECTIVES To identify sources for the aac(6')-Im fragment found in A. baumannii. METHODS MinION long-read sequencing and Unicycler hybrid assemblies were used to determine the genetic context of the aac(6')-Im gene. Quantitative reverse transcriptase PCR was used to measure expression. RESULTS Among >60 000 non-Acinetobacter draft genomes in the MRSN collection, the aac(6')-Im gene was detected in Pseudomonas putida and Enterobacter hormaechei isolates recovered from patients in Thailand between 2016 and 2019. Genomes of multiply resistant P. putida MRSN365855 and E. hormaechei MRSN791417 were completed. The class 1 integron containing the aac(6')-Im cassette was in the chromosome in MRSN365855, and in an HI2 plasmid in MRSN791417. However, MRSN791417 was amikacin susceptible and the gene was not expressed due to loss of the Pc promoter of the integron. Further examples of aac(6')-Im in plasmids from or the chromosome of various Gram-negative species were found in the GenBank nucleotide database. The aac(6')-Im context in integrons in pMRSN791417-8 and a Klebsiella plasmid pAMR200031 shared similarities with the aac(6')-Im region of AbGRI2-Im islands in A. baumannii. In other cases, the cassette array including the aac(6')-Im cassette was different. CONCLUSIONS The aac(6')-Im gene is widespread, being found so far in several different species and in several different gene cassette arrays. The lack of amikacin resistance in E. hormaechei highlights the importance of correlating resistance gene content and antibiotic resistance phenotype.
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Affiliation(s)
- Christopher J Harmer
- School of Life and Environmental Sciences, The University of Sydney, NSW, Australia
| | - Messiah J Nelson
- Multidrug Resistant Organism Repository and Surveillance Network, Walter Reed Army Institute of Research, Silver Spring, MD, USA
| | - Francois Lebreton
- Multidrug Resistant Organism Repository and Surveillance Network, Walter Reed Army Institute of Research, Silver Spring, MD, USA
| | - Paphavee Lertsethtakarn
- Bacterial and Parasitic Diseases Department, Armed Forces Research Institute of Medical Sciences (AFRIMS), Bangkok, Thailand
| | - Patrick T McGann
- Multidrug Resistant Organism Repository and Surveillance Network, Walter Reed Army Institute of Research, Silver Spring, MD, USA
| | - Ruth M Hall
- School of Life and Environmental Sciences, The University of Sydney, NSW, Australia
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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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Lukovic B, Kabic J, Dragicevic M, Kuljanin S, Dimkic I, Jovcic B, Gajic I. Genetic basis of antimicrobial resistance, virulence features and phylogenomics of carbapenem-resistant Acinetobacter baumannii clinical isolates. Infection 2024:10.1007/s15010-024-02316-8. [PMID: 38856809 DOI: 10.1007/s15010-024-02316-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2024] [Accepted: 06/03/2024] [Indexed: 06/11/2024]
Abstract
PURPOSE The worldwide emergence and clonal spread of carbapenem-resistant Acinetobacter baumannii (CRAB) is of great concern. In the present study, we determined the mechanisms of antimicrobial resistance, virulence gene repertoire and genomic relatedness of CRAB isolates circulating in Serbian hospitals. METHODS CRAB isolates were analyzed using whole-genome sequencing (WGS) for the presence of antimicrobial resistance-encoding genes, virulence factors-encoding genes, mobile genetic elements and genomic relatedness. Antimicrobial susceptibility testing was done by disk diffusion and broth microdilution methods. RESULTS Eleven isolates exhibited an MDR resistance phenotype, while four of them were XDR. MIC90 for meropenem and imipenem were > 64 µg/mL and 32 µg/mL, respectively. While all CRABs harbored blaOXA-66 variant of blaOXA-51 gene, those assigned to STPas2, STPas636 and STPas492 had blaADC-73,blaADC-74 and blaADC-30 variants, respectively. The following acquired carbapenemases-encoding genes were found: blaOXA-72 (n = 12), blaOXA-23 (n = 3), and blaNDM-1(n = 5), and were mapped to defined mobile genetic elements. MLST analysis assigned the analyzed CRAB isolates to three Pasteur sequence types (STs): STPas2, STPas492, and STPas636. The Majority of strains belonged to International Clone II (ICII) and carried tested virulence-related genes liable for adherence, biofilm formation, iron uptake, heme biosynthesis, zinc utilization, serum resistance, stress adaptation, intracellular survival and toxin activity. CONCLUSION WGS elucidated the resistance and virulence profiles of CRABs isolated from clinical samples in Serbian hospitals and genomic relatedness of CRAB isolates from Serbia and globally distributed CRABs.
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Affiliation(s)
- Bojana Lukovic
- College of Health Sciences, Academy of Applied Studies Belgrade, Cara Dusana 254, Belgrade, 11080, Serbia.
| | - Jovana Kabic
- Institute of Microbiology and Immunology, Faculty of Medicine, University of Belgrade, Belgrade, Serbia
| | - Milan Dragicevic
- Institute for Biological Research "Siniša Stanković", National Institute of the Republic of Serbia, University of Belgrade, Belgrade, Serbia
| | | | - Ivica Dimkic
- Faculty of Biology, University of Belgrade, Belgrade, Serbia
| | - Branko Jovcic
- Faculty of Biology, University of Belgrade, Belgrade, Serbia
- Laboratory for Molecular Microbiology, Institute of Molecular Genetics and Genetic Engineering, University of Belgrade, Belgrade, Serbia
| | - Ina Gajic
- Institute of Microbiology and Immunology, Faculty of Medicine, University of Belgrade, Belgrade, Serbia
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Tobin LA, Cain AK, Djordjevic SP, Hamidian M. Transposons Carrying the aacC2e Aminoglycoside and blaTEM Beta-Lactam Resistance Genes in Acinetobacter. Microb Drug Resist 2024; 30:273-278. [PMID: 38593463 DOI: 10.1089/mdr.2023.0299] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/11/2024] Open
Abstract
This study examines the genetic contexts and evolutionary steps responsible for the formation of the widely spread transposon Tn6925 carrying blaTEM and aacC2e, which confers resistance to beta-lactam and aminoglycoside antibiotics in Gram-negative bacteria. The blaTEM-1 and aacC2e genes were found in several transposons. They were first observed within an IS26 bounded 3.7 kb transposon (Tn6925) on several Acinetobacter baumannii plasmids located within a 4.7 kb dif module. Truncated and expanded variations of Tn6925 were found across other A. baumannii plasmids, as well as in other Gram-negative bacteria (including Vibrio cholerae). Moreover, blaTEM-1 and aacC2e were in much larger resistance-heavy transposons including the ISAba1-bounded 24.6 kb (here called Tn6927), found in an A. baumannii chromosome. A novel ISKpn12-bounded transposon was also observed to contain blaTEM and aacC2e which was found interrupting Tn5393 along with an IS26 pseudo-compound transposon to form a 24.9 kb resistance island in an Acinetobacter pittii plasmid. Multiple mobile genetic elements are involved in the formation of transposon structures that circulate blaTEM and aacC2e. Among these, IS26 and ISAba1 appear to have played a major role in the formation and spread of these elements in the Acinetobacter species.
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Affiliation(s)
- Liam A Tobin
- Australian Institute for Microbiology and Infection, University of Technology Sydney, Ultimo, Australia
| | - Amy K Cain
- ARC Centre of Excellence in Synthetic Biology, School of Natural Sciences, Macquarie University, Sydney, Australia
| | - Steven P Djordjevic
- Australian Institute for Microbiology and Infection, University of Technology Sydney, Ultimo, Australia
| | - Mehrad Hamidian
- Australian Institute for Microbiology and Infection, University of Technology Sydney, Ultimo, Australia
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Chai WC, Whittall JJ, Polyak SW, Foo K, Li X, Dutschke CJ, Ogunniyi AD, Ma S, Sykes MJ, Semple SJ, Venter H. Cinnamaldehyde derivatives act as antimicrobial agents against Acinetobacter baumannii through the inhibition of cell division. Front Microbiol 2022; 13:967949. [PMID: 36106080 PMCID: PMC9465178 DOI: 10.3389/fmicb.2022.967949] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2022] [Accepted: 08/05/2022] [Indexed: 11/13/2022] Open
Abstract
Acinetobacter baumannii is a pathogen with high intrinsic antimicrobial resistance while multidrug resistant (MDR) and extensively drug resistant (XDR) strains of this pathogen are emerging. Treatment options for infections by these strains are very limited, hence new therapies are urgently needed. The bacterial cell division protein, FtsZ, is a promising drug target for the development of novel antimicrobial agents. We have previously reported limited activity of cinnamaldehyde analogs against Escherichia coli. In this study, we have determined the antimicrobial activity of six cinnamaldehyde analogs for antimicrobial activity against A. baumannii. Microscopic analysis was performed to determine if the compounds inhibit cell division. The on-target effect of the compounds was assessed by analyzing their effect on polymerization and on the GTPase activity of purified FtsZ from A. baumannii. In silico docking was used to assess the binding of cinnamaldehyde analogs. Finally, in vivo and in vitro safety assays were performed. All six compounds displayed antibacterial activity against the critical priority pathogen A. baumannii, with 4-bromophenyl-substituted 4 displaying the most potent antimicrobial activity (MIC 32 μg/mL). Bioactivity was significantly increased in the presence of an efflux pump inhibitor for A. baumannii ATCC 19606 (up to 32-fold) and significantly, for extensively drug resistant UW 5075 (greater than 4-fold), suggesting that efflux contributes to the intrinsic resistance of A. baumannii against these agents. The compounds inhibited cell division in A. baumannii as observed by the elongated phenotype and targeted the FtsZ protein as seen from the inhibition of polymerization and GTPase activity. In silico docking predicted that the compounds bind in the interdomain cleft adjacent to the H7 core helix. Di-chlorinated 6 was devoid of hemolytic activity and cytotoxicity against mammalian cells in vitro, as well as adverse activity in a Caenorhabditis elegans nematode model in vivo. Together, these findings present halogenated analogs 4 and 6 as promising candidates for further development as antimicrobial agents aimed at combating A. baumannii. This is also the first report of FtsZ-targeting compounds with activity against an XDR A. baumannii strain.
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Affiliation(s)
- Wern Chern Chai
- Health and Biomedical Innovation, Clinical and Health Sciences, University of South Australia, Adelaide, SA, Australia
| | - Jonathan J. Whittall
- Health and Biomedical Innovation, Clinical and Health Sciences, University of South Australia, Adelaide, SA, Australia
| | - Steven W. Polyak
- Health and Biomedical Innovation, Clinical and Health Sciences, University of South Australia, Adelaide, SA, Australia
| | - Klyie Foo
- Health and Biomedical Innovation, Clinical and Health Sciences, University of South Australia, Adelaide, SA, Australia
| | - Xin Li
- Department of Medicinal Chemistry, Key Laboratory of Chemical Biology (Ministry of Education), School of Pharmaceutical Sciences, Cheeloo College of Medicine, Shandong University, Jinan, China
| | - Cameron J. Dutschke
- Health and Biomedical Innovation, Clinical and Health Sciences, University of South Australia, Adelaide, SA, Australia
| | - Abiodun D. Ogunniyi
- Australian Centre for Antimicrobial Resistance Ecology, School of Animal and Veterinary Sciences, University of Adelaide, Adelaide, SA, Australia
| | - Shutao Ma
- Department of Medicinal Chemistry, Key Laboratory of Chemical Biology (Ministry of Education), School of Pharmaceutical Sciences, Cheeloo College of Medicine, Shandong University, Jinan, China
| | - Matthew J. Sykes
- Health and Biomedical Innovation, Clinical and Health Sciences, University of South Australia, Adelaide, SA, Australia
| | - Susan J. Semple
- Health and Biomedical Innovation, Clinical and Health Sciences, University of South Australia, Adelaide, SA, Australia
- Quality Use of Medicines and Pharmacy Research Centre, Clinical and Health Sciences, University of South Australia, Adelaide, SA, Australia
| | - Henrietta Venter
- Health and Biomedical Innovation, Clinical and Health Sciences, University of South Australia, Adelaide, SA, Australia
- *Correspondence: Henrietta Venter,
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