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Derbyshire KM, Salfinger M. Plasmid-mediated drug resistance in mycobacteria: the tip of the iceberg? J Clin Microbiol 2023; 61:e0062823. [PMID: 37724858 PMCID: PMC10595058 DOI: 10.1128/jcm.00628-23] [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: 09/21/2023] Open
Abstract
Macrolides, such as clarithromycin, are crucial in the treatment of nontuberculous mycobacteria (NTM). NTM are notoriously innately drug resistant, which has made the dependence on macrolides for their treatment even more important. Not surprisingly, resistance to macrolides has been documented in some NTM, including Mycobacterium avium and Mycobacterium abscessus, which are the two NTM species most often identified in clinical isolates. Resistance is mediated by point mutations in the 23S ribosomal RNA or by methylation of the rRNA by a methylase (encoded by an erm gene). Chromosomally encoded erm genes have been identified in many of the macrolide-resistant isolates, but not in Mycobacterium chelonae. Now, Brown-Elliott et al. (J Clin Microbiol 61:e00428-23, 2023, https://doi.org/10.1128/JCM.00428-23) describe the identification of a new erm variant, erm(55), which was found either on the chromosome or on a plasmid in highly macrolide-resistant clinical isolates of M. chelonae. The chromosomal erm(55) gene appears to be associated with mobile elements; one gene is within a putative transposon and the second is in a large (37 kb) insertion/deletion. The plasmid carrying erm(55) also encodes type IV and type VII secretion systems, which are often linked on large mycobacterial plasmids and are hypothesized to mediate plasmid transfer. While the conjugative transfer of the erm(55)-containing plasmid between NTM has yet to be demonstrated, the inferences are clear, as evidenced by the dissemination of plasmid-mediated drug resistance in other medically important bacteria. Here, we discuss the findings of Brown-Elliott et al., and the potential ramifications on treatment of NTM infections.
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Affiliation(s)
- Keith M. Derbyshire
- Division of Genetics, Wadsworth Center, New York State Department of Health, Albany, New York, USA
- Department of Biomedical Sciences, University at Albany, Albany, New York, USA
| | - Max Salfinger
- College of Public Health, University of South Florida, Tampa, Florida, USA
- Division of Infectious Disease and International Medicine, Department of Internal Medicine, Morsani College of Medicine, University of South Florida, Tampa, Florida, USA
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2
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Brown-Elliott BA, Wallace RJ, Wengenack NL, Workman SD, Cameron ADS, Bush G, Hughes MD, Melton S, Gonzalez-Ramirez B, Rodriguez E, Somayaji K, Klapperich C, Viers M, Bolaji AJ, Rempel E, Alexander DC. Emergence of Inducible Macrolide Resistance in Mycobacterium chelonae Due to Broad-Host-Range Plasmid and Chromosomal Variants of the Novel 23S rRNA Methylase Gene, erm(55). J Clin Microbiol 2023; 61:e0042823. [PMID: 37347171 PMCID: PMC10358161 DOI: 10.1128/jcm.00428-23] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2023] [Accepted: 05/31/2023] [Indexed: 06/23/2023] Open
Abstract
Macrolides are a mainstay of therapy for infections due to nontuberculous mycobacteria (NTM). Among rapidly growing mycobacteria (RGM), inducible macrolide resistance is associated with four chromosomal 23S rRNA methylase (erm) genes. Beginning in 2018, we detected high-level inducible clarithromycin resistance (MICs of ≥16μg/mL) in clinical isolates of Mycobacterium chelonae, an RGM species not previously known to contain erm genes. Using whole-genome sequencing, we identified a novel plasmid-mediated erm gene. This gene, designated erm(55)P, exhibits <65% amino acid identity to previously described RGM erm genes. Two additional chromosomal erm(55) alleles, with sequence identities of 81% to 86% to erm(55)P, were also identified and designated erm(55)C and erm(55)T. The erm(55)T is part of a transposon. The erm(55)P allele variant is located on a putative 137-kb conjugative plasmid, pMchErm55. Evaluation of 133 consecutive isolates from 2020 to 2022 revealed 5 (3.8%) with erm(55). The erm(55)P gene was also identified in public data sets of two emerging pathogenic pigmented RGM species: Mycobacterium iranicum and Mycobacterium obuense, dating back to 2008. In both species, the gene appeared to be present on plasmids homologous to pMchErm55. Plasmid-mediated macrolide resistance, not described previously for any NTM species, appears to have spread to multiple RGM species. This has important implications for antimicrobial susceptibility guidelines and treatment of RGM infections. Further spread could present serious consequences for treatment of other macrolide-susceptible RGM. Additional studies are needed to determine the transmissibility of pMchErm55 and the distribution of erm(55) among other RGM species.
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Affiliation(s)
- Barbara A. Brown-Elliott
- Mycobacteria/Nocardia Research Laboratory, University of Texas Health Science Center at Tyler, Tyler, Texas, USA
| | - Richard J. Wallace
- Mycobacteria/Nocardia Research Laboratory, University of Texas Health Science Center at Tyler, Tyler, Texas, USA
| | - Nancy L. Wengenack
- Division of Clinical Microbiology, Mayo Clinic, Rochester, Minnesota, USA
| | - Sean D. Workman
- Department of Biology, University of Regina, Regina, Saskatchewan, Canada
| | | | - Georgie Bush
- Mycobacteria/Nocardia Research Laboratory, University of Texas Health Science Center at Tyler, Tyler, Texas, USA
| | - M. Dolores Hughes
- Mycobacteria/Nocardia Research Laboratory, University of Texas Health Science Center at Tyler, Tyler, Texas, USA
| | - Stephanie Melton
- Mycobacteria/Nocardia Research Laboratory, University of Texas Health Science Center at Tyler, Tyler, Texas, USA
| | - Bibiana Gonzalez-Ramirez
- Mycobacteria/Nocardia Research Laboratory, University of Texas Health Science Center at Tyler, Tyler, Texas, USA
| | - Eliana Rodriguez
- Mycobacteria/Nocardia Research Laboratory, University of Texas Health Science Center at Tyler, Tyler, Texas, USA
| | - Kavya Somayaji
- Mycobacteria/Nocardia Research Laboratory, University of Texas Health Science Center at Tyler, Tyler, Texas, USA
| | | | - Mary Viers
- Division of Clinical Microbiology, Mayo Clinic, Rochester, Minnesota, USA
| | - Ayooluwa J. Bolaji
- Cadham Provincial Laboratory, Diagnostic Services, Shared Health, Winnipeg, Manitoba, Canada
| | - Emma Rempel
- Cadham Provincial Laboratory, Diagnostic Services, Shared Health, Winnipeg, Manitoba, Canada
| | - David C. Alexander
- Cadham Provincial Laboratory, Diagnostic Services, Shared Health, Winnipeg, Manitoba, Canada
- Department of Medical Microbiology and Infectious Diseases, University of Manitoba, Winnipeg, Canada
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3
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Morgado S, Ramos NDV, Pereira BBDN, Freitas F, Fonseca ÉLD, Vicente AC. Multidrug-resistant Mycolicibacterium fortuitum infection in a companion cat (Felis silvestris catus) in Brazil. Access Microbiol 2022; 4:000317. [PMID: 35355875 PMCID: PMC8941956 DOI: 10.1099/acmi.0.000317] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2021] [Accepted: 12/09/2021] [Indexed: 11/24/2022] Open
Abstract
Mycolicibacterium fortuitum is a fast-growing bacterium and an opportunistic pathogen implicated in human and animal infections. Here we report the first case and genetic characterization of a strain of M. fortuitum isolated from skin lesions of a companion cat with atypical cutaneous mycobacteriosis in Brazil. In addition, the genome of this strain was sequenced, representing the first genome of this opportunistic pathogen isolated from an animal infection. The in silico and in vitro analysis regarding antibiotic resistance of this strain showed an intrinsic multiresistance antibiotic profile. However, this strain showed sensitivity to amikacin and ciprofloxacin, and the cat was treated long-term with these drugs.
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Affiliation(s)
- Sergio Morgado
- Fundação Oswaldo Cruz, Instituto Oswaldo Cruz, Laboratório de Genética Molecular de Microrganismos, Rio de Janeiro, Brazil
| | - Nilcéia de Veiga Ramos
- Universidade de Vassouras, Faculdade de Ciências Médicas de Maricá, Rio de Janeiro, Brazil
| | | | - Fernanda Freitas
- Fundação Oswaldo Cruz, Instituto Oswaldo Cruz, Laboratório de Genética Molecular de Microrganismos, Rio de Janeiro, Brazil
| | - Érica Lourenço da Fonseca
- Fundação Oswaldo Cruz, Instituto Oswaldo Cruz, Laboratório de Genética Molecular de Microrganismos, Rio de Janeiro, Brazil
| | - Ana Carolina Vicente
- Fundação Oswaldo Cruz, Instituto Oswaldo Cruz, Laboratório de Genética Molecular de Microrganismos, Rio de Janeiro, Brazil
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4
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Multiple genetic paths including massive gene amplification allow Mycobacterium tuberculosis to overcome loss of ESX-3 secretion system substrates. Proc Natl Acad Sci U S A 2022; 119:2112608119. [PMID: 35193958 PMCID: PMC8872769 DOI: 10.1073/pnas.2112608119] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/18/2021] [Indexed: 01/18/2023] Open
Abstract
The Mycobacterium tuberculosis (Mtb) ESX-3 type VII secretion system plays a critical role in iron acquisition. Infection of mice with highly attenuated Mtb deletion mutants lacking esxG or esxH, genes encoding key ESX-3 substrates, unexpectedly yielded suppressor mutants with restored capacity to grow in vivo and in vitro in the absence of iron supplementation. Whole-genome sequencing identified two mechanisms of suppression, the disruption of a transcriptional repressor that regulates expression of an ESX-3 paralogous region encoding EsxR and EsxS, and a massive 38- to 60-fold gene amplification of this same region. These data are significant because they reveal a previously unrecognized iron acquisition regulon and inform mechanisms of Mtb chromosome evolution. Mycobacterium tuberculosis (Mtb) possesses five type VII secretion systems (T7SS), virulence determinants that include the secretion apparatus and associated secretion substrates. Mtb strains deleted for the genes encoding substrates of the ESX-3 T7SS, esxG or esxH, require iron supplementation for in vitro growth and are highly attenuated in vivo. In a subset of infected mice, suppressor mutants of esxG or esxH deletions were isolated, which enabled growth to high titers or restored virulence. Suppression was conferred by mechanisms that cause overexpression of an ESX-3 paralogous region that lacks genes for the secretion apparatus but encodes EsxR and EsxS, apparent ESX-3 orphan substrates that functionally compensate for the lack of EsxG or EsxH. The mechanisms include the disruption of a transcriptional repressor and a massive 38- to 60-fold gene amplification. These data identify an iron acquisition regulon, provide insight into T7SS, and reveal a mechanism of Mtb chromosome evolution involving “accordion-type” amplification.
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5
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Bohr LL, Youngblom MA, Eldholm V, Pepperell CS. Genome reorganization during emergence of host-associated Mycobacterium abscessus. Microb Genom 2021; 7. [PMID: 34874249 PMCID: PMC8767326 DOI: 10.1099/mgen.0.000706] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Mycobacterium abscessus is a rapid growing, free-living species of bacterium that also causes lung infections in humans. Human infections are usually acquired from the environment; however, dominant circulating clones (DCCs) have emerged recently in both M. abscessus subsp. massiliense and subsp. abscessus that appear to be transmitted among humans and are now globally distributed. These recently emerged clones are potentially informative about the ecological and evolutionary mechanisms of pathogen emergence and host adaptation. The geographical distribution of DCCs has been reported, but the genomic processes underlying their transition from environmental bacterium to human pathogen are not well characterized. To address this knowledge gap, we delineated the structure of M. abscessus subspecies abscessus and massiliense using genomic data from 200 clinical isolates of M. abscessus from seven geographical regions. We identified differences in overall patterns of lateral gene transfer (LGT) and barriers to LGT between subspecies and between environmental and host-adapted bacteria. We further characterized genome reorganization that accompanied bacterial host adaptation, inferring selection pressures acting at both genic and intergenic loci. We found that both subspecies encode an expansive pangenome with many genes at rare frequencies. Recombination appears more frequent in M. abscessus subsp. massiliense than in subsp. abscessus, consistent with prior reports. We found evidence suggesting that phage are exchanged between subspecies, despite genetic barriers evident elsewhere throughout the genome. Patterns of LGT differed according to niche, with less LGT observed among host-adapted DCCs versus environmental bacteria. We also found evidence suggesting that DCCs are under distinct selection pressures at both genic and intergenic sites. Our results indicate that host adaptation of M. abscessus was accompanied by major changes in genome evolution, including shifts in the apparent frequency of LGT and impacts of selection. Differences were evident among the DCCs as well, which varied in the degree of gene content remodelling, suggesting they were placed differently along the evolutionary trajectory toward host adaptation. These results provide insight into the evolutionary forces that reshape bacterial genomes as they emerge into the pathogenic niche.
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Affiliation(s)
- Lindsey L Bohr
- Department of Medical Microbiology and Immunology, School of Medicine and Public Health, University of Wisconsin-Madison, Madison, WI, USA
| | - Madison A Youngblom
- Department of Medical Microbiology and Immunology, School of Medicine and Public Health, University of Wisconsin-Madison, Madison, WI, USA
| | | | - Caitlin S Pepperell
- Department of Medical Microbiology and Immunology, School of Medicine and Public Health, University of Wisconsin-Madison, Madison, WI, USA.,Department of Medicine, School of Medicine and Public Health, University of Wisconsin-Madison, Madison, WI, USA
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6
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Morgado SM, Paulo Vicente AC. Genomics of Atlantic Forest Mycobacteriaceae strains unravels a mobilome diversity with a novel integrative conjugative element and plasmids harbouring T7SS. Microb Genom 2021; 6. [PMID: 32496186 PMCID: PMC7478629 DOI: 10.1099/mgen.0.000382] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Mobile genetic elements (MGEs) are agents of bacterial evolution and adaptation. Genome sequencing provides an unbiased approach that has revealed an abundance of MGEs in prokaryotes, mainly plasmids and integrative conjugative elements. Nevertheless, many mobilomes, particularly those from environmental bacteria, remain underexplored despite their representing a reservoir of genes that can later emerge in the clinic. Here, we explored the mobilome of the Mycobacteriaceae family, focusing on strains from Brazilian Atlantic Forest soil. Novel Mycolicibacterium and Mycobacteroides strains were identified, with the former ones harbouring linear and circular plasmids encoding the specialized type-VII secretion system (T7SS) and mobility-associated genes. In addition, we also identified a T4SS-mediated integrative conjugative element (ICEMyc226) encoding two T7SSs and a number of xenobiotic degrading genes. Our study uncovers the diversity of the Mycobacteriaceae mobilome, providing the evidence of an ICE in this bacterial family. Moreover, the presence of T7SS genes in an ICE, as well as plasmids, highlights the role of these mobile genetic elements in the dispersion of T7SS.
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7
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Morgado SM, Vicente ACP. Comprehensive in silico survey of the Mycolicibacterium mobilome reveals an as yet underexplored diversity. Microb Genom 2021; 7:mgen000533. [PMID: 33620305 PMCID: PMC8190616 DOI: 10.1099/mgen.0.000533] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2020] [Accepted: 01/28/2021] [Indexed: 11/30/2022] Open
Abstract
The mobilome plays a crucial role in bacterial adaptation and is therefore a starting point to understand and establish the gene flow occurring in the process of bacterial evolution. This is even more so if we consider that the mobilome of environmental bacteria can be the reservoir of genes that may later appear in the clinic. Recently, new genera have been proposed in the family Mycobacteriaceae, including the genus Mycolicibacterium, which encompasses dozens of species of agricultural, biotechnological, clinical and ecological importance, being ubiquitous in several environments. The current scenario in the Mycobacteriaceae mobilome has some bias because most of the characterized mycobacteriophages were isolated using a single host strain, and the few plasmids reported mainly relate to the genus Mycobacterium. To fill in the gaps in these issues, we performed a systematic in silico study of these mobile elements based on 242 available genomes of the genus Mycolicibacterium. The analyses identified 156 putative plasmids (19 conjugative, 45 mobilizable and 92 non-mobilizable) and 566 prophages in 86 and 229 genomes, respectively. Moreover, a contig was characterized by resembling an actinomycete integrative and conjugative element (AICE). Within this diversity of mobile genetic elements, there is a pool of genes associated with several canonical functions, in addition to adaptive traits, such as virulence and resistance to antibiotics and metals (mercury and arsenic). The type-VII secretion system was a common feature in the predicted plasmids, being associated with genes encoding virulent proteins (EsxA, EsxB, PE and PPE). In addition to the characterization of plasmids and prophages of the family Mycobacteriaceae, this study showed an abundance of these genetic elements in a dozen species of the genus Mycolicibacterium.
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8
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Holt KE, McAdam P, Thai PVK, Thuong NTT, Ha DTM, Lan NN, Lan NH, Nhu NTQ, Hai HT, Ha VTN, Thwaites G, Edwards DJ, Nath AP, Pham K, Ascher DB, Farrar J, Khor CC, Teo YY, Inouye M, Caws M, Dunstan SJ. Frequent transmission of the Mycobacterium tuberculosis Beijing lineage and positive selection for the EsxW Beijing variant in Vietnam. Nat Genet 2018; 50:849-856. [PMID: 29785015 PMCID: PMC6143168 DOI: 10.1038/s41588-018-0117-9] [Citation(s) in RCA: 126] [Impact Index Per Article: 21.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2016] [Accepted: 03/22/2018] [Indexed: 12/19/2022]
Abstract
To examine the transmission dynamics of Mycobacterium tuberculosis (Mtb) isolated from tuberculosis patients in Ho Chi Minh City, Vietnam, we sequenced the whole genomes of 1,635 isolates and compared these with 3,144 isolates from elsewhere. The data identify an underlying burden of disease caused by the endemic Mtb lineage 1 associated with the activation of long-term latent infection, and a threefold higher burden associated with the more recently introduced Beijing lineage and lineage 4 Mtb strains. We find that Beijing lineage Mtb is frequently transferred between Vietnam and other countries, and detect higher levels of transmission of Beijing lineage strains within this host population than the endemic lineage 1 Mtb. Screening for parallel evolution of Beijing lineage-associated SNPs in other Mtb lineages as a signal of positive selection, we identify an alteration in the ESX-5 type VII-secreted protein EsxW, which could potentially contribute to the enhanced transmission of Beijing lineage Mtb in Vietnamese and other host populations.
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Affiliation(s)
- Kathryn E Holt
- Department of Biochemistry and Molecular Biology, Bio 21 Molecular Science and Biotechnology Institute, University of Melbourne, Parkville, Victoria, Australia.
| | - Paul McAdam
- Department of Biochemistry and Molecular Biology, Bio 21 Molecular Science and Biotechnology Institute, University of Melbourne, Parkville, Victoria, Australia
| | - Phan Vuong Khac Thai
- Pham Ngoc Thach Hospital for Tuberculosis and Lung Disease, Ho Chi Minh City, Vietnam
| | | | - Dang Thi Minh Ha
- Pham Ngoc Thach Hospital for Tuberculosis and Lung Disease, Ho Chi Minh City, Vietnam
| | - Nguyen Ngoc Lan
- Pham Ngoc Thach Hospital for Tuberculosis and Lung Disease, Ho Chi Minh City, Vietnam
| | - Nguyen Huu Lan
- Pham Ngoc Thach Hospital for Tuberculosis and Lung Disease, Ho Chi Minh City, Vietnam
| | | | - Hoang Thanh Hai
- Oxford University Clinical Research Unit, Ho Chi Minh City, Vietnam
| | - Vu Thi Ngoc Ha
- Oxford University Clinical Research Unit, Ho Chi Minh City, Vietnam
| | - Guy Thwaites
- Oxford University Clinical Research Unit, Ho Chi Minh City, Vietnam
- Centre for Tropical Medicine, Nuffield Department of Clinical Medicine, Oxford University, Oxford, UK
| | - David J Edwards
- Department of Biochemistry and Molecular Biology, Bio 21 Molecular Science and Biotechnology Institute, University of Melbourne, Parkville, Victoria, Australia
| | - Artika P Nath
- Department of Microbiology and Immunology, University of Melbourne, Parkville, Victoria, Australia
- Systems Genomics Lab, Baker Heart and Diabetes Institute, Melbourne, Victoria, Australia
| | - Kym Pham
- Department of Clinical Pathology, University of Melbourne, Parkville, Victoria, Australia
| | - David B Ascher
- Department of Biochemistry and Molecular Biology, Bio 21 Molecular Science and Biotechnology Institute, University of Melbourne, Parkville, Victoria, Australia
| | - Jeremy Farrar
- Oxford University Clinical Research Unit, Ho Chi Minh City, Vietnam
- Centre for Tropical Medicine, Nuffield Department of Clinical Medicine, Oxford University, Oxford, UK
| | - Chiea Chuen Khor
- Genome Institute of Singapore, Singapore, Singapore
- Singapore Eye Research Institute, Singapore, Singapore
| | - Yik Ying Teo
- Department of Statistics and Applied Probability, National University of Singapore, Singapore, Singapore
- Saw Swee Hock School of Public Health, National University of Singapore, Singapore, Singapore
| | - Michael Inouye
- Systems Genomics Lab, Baker Heart and Diabetes Institute, Melbourne, Victoria, Australia
- Department of Clinical Pathology, University of Melbourne, Parkville, Victoria, Australia
- Department of Public Health and Primary Care, University of Cambridge, Strangeways Research Laboratories, Cambridge, UK
| | - Maxine Caws
- Department of Clinical Sciences, Liverpool School of Tropical Medicine, Liverpool, UK
- Birat-Nepal Medical Trust, Kathmandu, Nepal
| | - Sarah J Dunstan
- Peter Doherty Institute for Infection and Immunity, University of Melbourne, Parkville, Victoria, Australia.
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9
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Frequent transmission of the Mycobacterium tuberculosis Beijing lineage and positive selection for the EsxW Beijing variant in Vietnam. Nat Genet 2018. [PMID: 29785015 DOI: 10.1038/s41588-018-0117-9.] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
To examine the transmission dynamics of Mycobacterium tuberculosis (Mtb) isolated from tuberculosis patients in Ho Chi Minh City, Vietnam, we sequenced the whole genomes of 1,635 isolates and compared these with 3,144 isolates from elsewhere. The data identify an underlying burden of disease caused by the endemic Mtb lineage 1 associated with the activation of long-term latent infection, and a threefold higher burden associated with the more recently introduced Beijing lineage and lineage 4 Mtb strains. We find that Beijing lineage Mtb is frequently transferred between Vietnam and other countries, and detect higher levels of transmission of Beijing lineage strains within this host population than the endemic lineage 1 Mtb. Screening for parallel evolution of Beijing lineage-associated SNPs in other Mtb lineages as a signal of positive selection, we identify an alteration in the ESX-5 type VII-secreted protein EsxW, which could potentially contribute to the enhanced transmission of Beijing lineage Mtb in Vietnamese and other host populations.
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10
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Gray TA, Derbyshire KM. Blending genomes: distributive conjugal transfer in mycobacteria, a sexier form of HGT. Mol Microbiol 2018; 108:601-613. [PMID: 29669186 DOI: 10.1111/mmi.13971] [Citation(s) in RCA: 42] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/14/2018] [Indexed: 12/16/2022]
Abstract
This review discusses a novel form of horizontal gene transfer (HGT) found in mycobacteria called Distributive Conjugal Transfer (DCT). While satisfying the criteria for conjugation, DCT occurs by a mechanism so distinct from oriT-mediated conjugation that it could be considered a fourth category of HGT. DCT involves the transfer of chromosomal DNA between mycobacteria and, most significantly, generates transconjugants with mosaic genomes of the parental strains. Multiple segments of donor chromosomal DNA can be co-transferred regardless of their location or the genetic selection and, as a result, the transconjugant genome contains many donor-derived segments; hence the name DCT. This distinguishing feature of DCT separates it from the other known mechanisms of HGT, which generally result in the introduction of a single, defined segment of DNA into the recipient chromosome (Fig. ). Moreover, these mosaic progeny are generated from a single conjugal event, which provides enormous capacity for rapid adaptation and evolution, again distinguishing it from the three classical modes of HGT. Unsurprisingly, the unusual mosaic products of DCT are generated by a conjugal mechanism that is also unusual. Here, we will describe the unique features of DCT and contrast those to other mechanisms of HGT, both from a mechanistic and an evolutionary perspective. Our focus will be on transfer of chromosomal DNA, as opposed to plasmid mobilization, because DCT mediates transfer of chromosomal DNA and is a chromosomally encoded process.
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Affiliation(s)
- Todd A Gray
- New York State Department of Health, Wadsworth Center, Albany, NY 12201, USA.,Department of Biomedical Sciences, University at Albany, Albany, NY 12201, USA
| | - Keith M Derbyshire
- New York State Department of Health, Wadsworth Center, Albany, NY 12201, USA.,Department of Biomedical Sciences, University at Albany, Albany, NY 12201, USA
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