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Bissonnette N, Brousseau JP, Ollier S, Byrne AS, Ibeagha-Awemu EM, Tahlan K. Systematic assessment of the reliability of quantitative PCR assays targeting IS900 for the detection of Mycobacterium avium ssp. paratuberculosis presence in animal and environmental samples. J Dairy Sci 2024; 107:7165-7184. [PMID: 38754821 DOI: 10.3168/jds.2023-24566] [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] [Received: 12/18/2023] [Accepted: 03/27/2024] [Indexed: 05/18/2024]
Abstract
Mycobacterium avium ssp. paratuberculosis (MAP) is the bacterium responsible for causing Johne's disease (JD), which is endemic to dairy cattle and also implicated in the etiology of Crohn's disease. The difficulty in diagnosing asymptomatic cows for JD makes this disease hard to control. Johne's disease is considered a priority under the One Health approach to prevent the spread of the causative agent to humans. Environmental screening is a strategic approach aimed at identifying dairy herds with animals infected with MAP. It serves as the initial step toward implementing more intensive actions to control the disease. Quantitative PCR (qPCR) technology is widely used for diagnosis. Given that genome sequencing is now much more accessible than ever before, it is possible to target regions of the MAP genome that allow for the greatest diagnostic sensitivity and specificity. The aim of this study was to identify among the published qPCR assays targeting IS900 the more cost-effective options to detect MAP and to validate them in the diagnostic context of JD. Mycobacterium avium ssp. paratuberculosis IS900 is a prime target because it is a multicopy genetic element. A total of 136 publications have reported on the use of IS900 qPCR assays over the past 3 decades. Among these records, 29 used the SYBR Green chemistry, and 107 used TaqMan technology. Aside from the 9 reports using commercial assays, 72 TaqMan reports cited previously published work, leaving us with 27 TaqMan qPCR designs. Upon closer examination, 5 TaqMan designs contained mismatches in primer or probe sequences. Additionally, others exhibited high similarity to environmental microorganisms or non-MAP mycobacteria. We assessed the performance of 6 IS900 qPCR designs and their sensitivity when applied to clinical or environmental samples, which varied from 4 to 56 fold overall. Additionally, we provide recommendations for testing clinical and environmental samples, as certain strategies used previously should be avoided due to poor qPCR design (e.g., the presence of mismatches) or a lack of specificity.
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Affiliation(s)
- N Bissonnette
- Sherbrooke Research and Development Centre, Agriculture and Agri-Food Canada, Sherbrooke, QC J1M 0C8, Canada.
| | - J-P Brousseau
- Sherbrooke Research and Development Centre, Agriculture and Agri-Food Canada, Sherbrooke, QC J1M 0C8, Canada
| | - S Ollier
- Sherbrooke Research and Development Centre, Agriculture and Agri-Food Canada, Sherbrooke, QC J1M 0C8, Canada
| | - A S Byrne
- Department of Biology, Memorial University of Newfoundland, St. John's, NL A1C 5S7, Canada
| | - E M Ibeagha-Awemu
- Sherbrooke Research and Development Centre, Agriculture and Agri-Food Canada, Sherbrooke, QC J1M 0C8, Canada
| | - K Tahlan
- Department of Biology, Memorial University of Newfoundland, St. John's, NL A1C 5S7, Canada
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2
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Mizzi R, Plain KM, Timms VJ, Marsh I, Whittington RJ. Characterisation of IS1311 in Mycobacterium avium subspecies paratuberculosis genomes: Typing, continental clustering, microbial evolution and host adaptation. PLoS One 2024; 19:e0294570. [PMID: 38349924 PMCID: PMC10863896 DOI: 10.1371/journal.pone.0294570] [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: 08/14/2023] [Accepted: 11/04/2023] [Indexed: 02/15/2024] Open
Abstract
Johne's disease (JD), caused by Mycobacterium avium subspecies paratuberculosis (MAP) is a global burden for livestock producers and has an association with Crohn's disease in humans. Within MAP there are two major lineages, S/Type I/TypeIII and C/Type II, that vary in phenotype including culturability, host preference and virulence. These lineages have been identified using the IS1311 element, which contains a conserved, single nucleotide polymorphism. IS1311 and the closely related IS1245 element belong to the IS256 family of insertion sequences, are dispersed throughout M. avium taxa but remain poorly characterised. To investigate the distribution and diversity of IS1311 in MAP, 805 MAP genomes were collated from public databases. IS1245 was absent, while IS1311 sequence, copy number and insertion loci were conserved between MAP S lineages and varied within the MAP C lineage. One locus was specific to the S strains, which contained nine IS1311 copies. In contrast, C strains contained either seven or eight IS1311 loci. Most insertion loci were associated with the boundaries of homologous regions that had undergone genome rearrangement between the MAP lineages, suggesting that this sequence may be a driver of recombination. Phylogenomic geographic clustering of MAP subtypes was demonstrated for the first time, at continental scale, and indicated that there may have been recent MAP transmission between Europe and North America, in contrast to Australia where importation of live ruminants is generally prohibited. This investigation confirmed the utility of IS1311 typing in epidemiological studies and resolved anomalies in past studies. The results shed light on potential mechanisms of niche/host adaptation, virulence of MAP and global transmission dynamics.
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Affiliation(s)
- Rachel Mizzi
- School of Veterinary Science, Faculty of Science, The University of Sydney, Sydney, New South Wales, Australia
| | - Karren M. Plain
- School of Veterinary Science, Faculty of Science, The University of Sydney, Sydney, New South Wales, Australia
| | - Verlaine J. Timms
- Neilan Laboratory of Microbial and Molecular Diversity, College of Engineering, Science and Environment, The University of Newcastle, New South Wales, Australia
| | - Ian Marsh
- Microbiology and Parasitology Research, Elizabeth Macarthur Agricultural Institute, Menangle, New South Wales, Australia
| | - Richard J. Whittington
- School of Veterinary Science, Faculty of Science, The University of Sydney, Sydney, New South Wales, Australia
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3
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Honda JR. Environmental Sources and Transmission of Nontuberculous Mycobacteria. Clin Chest Med 2023; 44:661-674. [PMID: 37890909 DOI: 10.1016/j.ccm.2023.07.001] [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: 10/29/2023]
Abstract
The field of environmental nontuberculous mycobacteria (NTM) is benefiting from a new era of genomics that has catapulted our understanding of preferred niches, transmission, and outbreak investigations. The ability to forecast environmental features that promote or reduce environmental NTM prevalence will greatly improve with coordinated environmental sampling and by elevating the necessity for uniform disease notifications. Studies that synergize environmental biology, isolate notifications, and comparative genomics in prospective, longitudinal studies, particularly during climate changes and weather events, will be useful to solve longstanding NTM public health quandaries.
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Affiliation(s)
- Jennifer R Honda
- Department of Cellular and Molecular Biology, University of Texas Health Science Center at Tyler, 11937 US Hwy 271, BMR Building, Tyler, TX 75708, USA.
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4
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Carneiro S, Pinto M, Silva S, Santos A, Rodrigues I, Santos D, Duarte S, Vieira L, Gomes JP, Macedo R. Genome-Scale Characterization of Mycobacterium abscessus Complex Isolates from Portugal. Int J Mol Sci 2023; 24:15402. [PMID: 37895081 PMCID: PMC10606986 DOI: 10.3390/ijms242015402] [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] [Received: 09/27/2023] [Revised: 10/12/2023] [Accepted: 10/20/2023] [Indexed: 10/29/2023] Open
Abstract
The Mycobacterium abscessus complex (MABC) is an emerging, difficult to treat, multidrug-resistant nontuberculous mycobacteria responsible for a wide spectrum of infections and associated with an increasing number of cases worldwide. Dominant circulating clones (DCCs) of MABC have been genetically identified as groups of strains associated with higher prevalence, higher levels of antimicrobial resistance, and worse clinical outcomes. To date, little is known about the genomic characteristics of MABC species circulating in Portugal. Here, we examined the genetic diversity and antimicrobial resistance profiles of 30 MABC strains isolated between 2014 and 2022 in Portugal. The genetic diversity of circulating MABC strains was assessed through a gene-by-gene approach (wgMLST), allowing their subspecies differentiation and the classification of isolates into DCCs. Antimicrobial resistance profiles were defined using phenotypic, molecular, and genomic approaches. The majority of isolates were resistant to at least two antimicrobials, although a poor correlation between phenotype and genotype data was observed. Portuguese genomes were highly diverse, and data suggest the existence of MABC lineages with potential international circulation or cross-border transmission. This study highlights the genetic diversity and antimicrobial resistance profile of circulating MABC isolates in Portugal while representing the first step towards the implementation of a genomic-based surveillance system for MABC at the Portuguese NIH.
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Affiliation(s)
- Sofia Carneiro
- National Reference Laboratory for Mycobacteria, Department of Infectious Diseases, National Institute of Health Doutor Ricardo Jorge (INSA), 1649-016 Lisbon, Portugal; (S.C.); (A.S.)
- Department of Life Science, NOVA School of Science and Technology, NOVA University Lisbon, 2829-516 Lisbon, Portugal
| | - Miguel Pinto
- Genomics and Bioinformatics Unit, Department of Infectious Diseases, National Institute of Health Doutor Ricardo Jorge (INSA), 1649-016 Lisbon, Portugal; (M.P.); (J.P.G.)
| | - Sónia Silva
- National Reference Laboratory for Mycobacteria, Department of Infectious Diseases, National Institute of Health Doutor Ricardo Jorge (INSA), 1649-016 Lisbon, Portugal; (S.C.); (A.S.)
| | - Andrea Santos
- National Reference Laboratory for Mycobacteria, Department of Infectious Diseases, National Institute of Health Doutor Ricardo Jorge (INSA), 1649-016 Lisbon, Portugal; (S.C.); (A.S.)
| | - Irene Rodrigues
- National Reference Laboratory for Mycobacteria, Department of Infectious Diseases, National Institute of Health Doutor Ricardo Jorge (INSA), 1649-016 Lisbon, Portugal; (S.C.); (A.S.)
| | - Daniela Santos
- Technology and Innovation Unit, Department of Human Genetics, National Institute of Health Doutor Ricardo Jorge (INSA), 1649-016 Lisbon, Portugal; (D.S.); (S.D.)
| | - Sílvia Duarte
- Technology and Innovation Unit, Department of Human Genetics, National Institute of Health Doutor Ricardo Jorge (INSA), 1649-016 Lisbon, Portugal; (D.S.); (S.D.)
| | - Luís Vieira
- Technology and Innovation Unit, Department of Human Genetics, National Institute of Health Doutor Ricardo Jorge (INSA), 1649-016 Lisbon, Portugal; (D.S.); (S.D.)
| | - João Paulo Gomes
- Genomics and Bioinformatics Unit, Department of Infectious Diseases, National Institute of Health Doutor Ricardo Jorge (INSA), 1649-016 Lisbon, Portugal; (M.P.); (J.P.G.)
- Veterinary and Animal Research Centre (CECAV), Faculty of Veterinary Medicine, Lusófona University, 376 Campo Grande, 1749-024 Lisbon, Portugal
| | - Rita Macedo
- National Reference Laboratory for Mycobacteria, Department of Infectious Diseases, National Institute of Health Doutor Ricardo Jorge (INSA), 1649-016 Lisbon, Portugal; (S.C.); (A.S.)
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Duffy SC, Lupien A, Elhaji Y, Farag M, Marcus V, Behr MA. Establishment of persistent enteric mycobacterial infection following streptomycin pre-treatment. Gut Pathog 2023; 15:46. [PMID: 37789445 PMCID: PMC10546655 DOI: 10.1186/s13099-023-00573-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/23/2023] [Accepted: 09/21/2023] [Indexed: 10/05/2023] Open
Abstract
Mycobacterium avium subsp. paratuberculosis (MAP) is the causative agent of paratuberculosis, a chronic gastrointestinal disease affecting ruminants. This disease remains widespread in part due to the limitations of available diagnostics and vaccines. A representative small animal model of disease could act as a valuable tool for studying its pathogenesis and to develop new methods for paratuberculosis control, but current models are lacking. Streptomycin pre-treatment can reduce colonization resistance and has previously been shown to improve enteric infection in a Salmonella model. Here, we investigated whether streptomycin pre-treatment of mice followed by MAP gavage could act as a model of paratuberculosis which mimics the natural route of infection and disease development in ruminants. The infection outcomes of MAP were compared to M. avium subsp. hominissuis (MAH), an environmental mycobacterium, and M. bovis and M. orygis, two tuberculous mycobacteria. Streptomycin pre-treatment was shown to consistently improve bacterial infection post-oral inoculation. This model led to chronic MAP infection of the intestines and mesenteric lymph nodes (MLNs) up to 24-weeks post-gavage, however there was no evidence of inflammation or disease. These infection outcomes were found to be specific to MAP. When the model was applied to a bacterium of lesser virulence MAH, the infection was comparatively transient. Mice infected with bacteria of greater virulence, M. bovis or M. orygis, developed chronic intestinal and MLN infection with pulmonary disease similar to zoonotic TB. Our findings suggest that a streptomycin pre-treatment mouse model could be applied to future studies to improve enteric infection with MAP and to investigate other modifications underlying MAP enteritis.
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Affiliation(s)
- Shannon C Duffy
- Department of Microbiology and Immunology, McGill University, Montreal, QC, Canada
- McGill International TB Centre, Montreal, QC, Canada
- The Infectious Diseases and Immunity in Global Health Program, The Research Institute of the McGill University Health Centre, Montreal, QC, Canada
| | - Andréanne Lupien
- Department of Microbiology and Immunology, McGill University, Montreal, QC, Canada
- McGill International TB Centre, Montreal, QC, Canada
- The Infectious Diseases and Immunity in Global Health Program, The Research Institute of the McGill University Health Centre, Montreal, QC, Canada
- Department of Medicine, McGill University, Montreal, QC, Canada
| | - Youssef Elhaji
- Diagnostic Genomic Division, Department of Laboratory Medicine and Pathology, Hamad Medical Corporation, Doha, Qatar
| | - Mina Farag
- Department of Pathology, McGill University, Montreal, QC, Canada
- Department of Laboratory Medicine, Division of Pathology, McGill University Health Center, Montreal, QC, Canada
| | - Victoria Marcus
- Department of Pathology, McGill University, Montreal, QC, Canada
- Department of Laboratory Medicine, Division of Pathology, McGill University Health Center, Montreal, QC, Canada
| | - Marcel A Behr
- Department of Microbiology and Immunology, McGill University, Montreal, QC, Canada.
- McGill International TB Centre, Montreal, QC, Canada.
- The Infectious Diseases and Immunity in Global Health Program, The Research Institute of the McGill University Health Centre, Montreal, QC, Canada.
- Department of Medicine, McGill University, Montreal, QC, Canada.
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Orłowska B, Majchrzak M, Didkowska A, Anusz K, Krajewska-Wędzina M, Zabost A, Brzezińska S, Kozińska M, Augustynowicz-Kopeć E, Urbańska K, Welz M, Parniewski P. Mycobacterial Interspersed Repeat Unit-Variable Number Tandem Repeat Typing of Mycobacterium avium Strains Isolated from the Lymph Nodes of Free-Living Carnivorous Animals in Poland. Pathogens 2023; 12:1184. [PMID: 37764992 PMCID: PMC10536629 DOI: 10.3390/pathogens12091184] [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: 08/23/2023] [Revised: 09/14/2023] [Accepted: 09/17/2023] [Indexed: 09/29/2023] Open
Abstract
Non-tuberculous mycobacteria (NTM) are ubiquitous organisms, of which some, especially those of the Mycobacterium avium complex (MAC), may be opportunistic animal and human pathogens. Infection with NTM can interfere with tuberculosis (TB) diagnosis and induce zoonoses, especially in immunocompromised individuals. Diseases caused by NTM have become more readily recognized; however, they are likely still underestimated. In this study, we identified and genotyped Mycobacterium avium strains that were isolated during TB monitoring among free-living carnivorous animals from southeastern Poland. In 2011-2020, lymph node samples from 192 such animals were tested for mycobacteria. A total of 41 isolates of M. avium strains were detected with the use of IS901, IS900, IS1245, and mycobacterial interspersed repeat unit-variable number tandem repeat (MIRU-VNTR) identification. Thirty-three were identified as M. avium subsp. avium. These strains were derived from 1 beech marten (Martes foina), 1 common buzzard (Buteo buteo), 2 European badgers (Meles meles), 3 wolves (Canis lupus), and 26 red foxes (Vulpes vulpes). One strain isolated from a wolf was identified as M. avium subsp. hominissuis. The results show the widespread occurrence of MAC bacilli in the studied environment and additionally comprise new data on the molecular characteristics of M. avium subspecies carried by free-living southeastern Polish carnivores.
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Affiliation(s)
- Blanka Orłowska
- Department of Food Hygiene and Public Health Protection, Institute of Veterinary Medicine, Warsaw University of Life Sciences (SGGW), Nowoursynowska 159, 02-776 Warsaw, Poland; (A.D.); (K.A.)
| | - Marta Majchrzak
- Institute of Medical Biology, Polish Academy of Sciences, Lodowa 106, 93-232 Lodz, Poland
| | - Anna Didkowska
- Department of Food Hygiene and Public Health Protection, Institute of Veterinary Medicine, Warsaw University of Life Sciences (SGGW), Nowoursynowska 159, 02-776 Warsaw, Poland; (A.D.); (K.A.)
| | - Krzysztof Anusz
- Department of Food Hygiene and Public Health Protection, Institute of Veterinary Medicine, Warsaw University of Life Sciences (SGGW), Nowoursynowska 159, 02-776 Warsaw, Poland; (A.D.); (K.A.)
| | - Monika Krajewska-Wędzina
- Department of Microbiology, National Veterinary Research Institute, Aleja Partyzantów 57, 24-100 Puławy, Poland;
| | - Anna Zabost
- Department of Microbiology, National Tuberculosis Reference Laboratory, National Tuberculosis and Lung Diseases Research Institute, Płocka 26, 01-138 Warsaw, Poland; (A.Z.); (S.B.); (M.K.); (E.A.-K.)
| | - Sywia Brzezińska
- Department of Microbiology, National Tuberculosis Reference Laboratory, National Tuberculosis and Lung Diseases Research Institute, Płocka 26, 01-138 Warsaw, Poland; (A.Z.); (S.B.); (M.K.); (E.A.-K.)
| | - Monika Kozińska
- Department of Microbiology, National Tuberculosis Reference Laboratory, National Tuberculosis and Lung Diseases Research Institute, Płocka 26, 01-138 Warsaw, Poland; (A.Z.); (S.B.); (M.K.); (E.A.-K.)
| | - Ewa Augustynowicz-Kopeć
- Department of Microbiology, National Tuberculosis Reference Laboratory, National Tuberculosis and Lung Diseases Research Institute, Płocka 26, 01-138 Warsaw, Poland; (A.Z.); (S.B.); (M.K.); (E.A.-K.)
| | - Kaja Urbańska
- Department of Morphological Sciences, Division of Histology and Embryology, Institute of Veterinary Medicine, Warsaw University of Life Sciences (SGGW), Nowoursynowska 159, 02-776 Warsaw, Poland;
| | - Mirosław Welz
- Provincial Veterinary Inspectorate, Piotra Ścigiennego 6a, 38-400 Krosno, Poland;
| | - Paweł Parniewski
- Institute of Medical Biology, Polish Academy of Sciences, Lodowa 106, 93-232 Lodz, Poland
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Byrne A, Bissonnette N, Ollier S, Tahlan K. Investigating in vivo Mycobacterium avium subsp. paratuberculosis microevolution and mixed strain infections. Microbiol Spectr 2023; 11:e0171623. [PMID: 37584606 PMCID: PMC10581078 DOI: 10.1128/spectrum.01716-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2023] [Accepted: 07/10/2023] [Indexed: 08/17/2023] Open
Abstract
Mycobacterium avium subsp. paratuberculosis (MAP) causes Johne's Disease (JD) in ruminants, which is responsible for significant economic loss to the global dairy industry. Mixed strain infection (MSI) refers to the concurrent infection of a susceptible host with genetically distinct strains of a pathogen, whereas within-host changes in an infecting strain leading to genetically distinguishable progeny is called microevolution. The two processes can influence host-pathogen dynamics, disease progression and outcomes, but not much is known about their prevalence and impact on JD. Therefore, we obtained up to 10 MAP isolates each from 14 high-shedding animals and subjected them to whole-genome sequencing. Twelve of the 14 animals examined showed evidence for the presence of MSIs and microevolution, while the genotypes of MAP isolates from the remaining two animals could be attributed solely to microevolution. All MAP isolates that were otherwise isogenic had differences in short sequence repeats (SSRs), of which SSR1 and SSR2 were the most diverse and homoplastic. Variations in SSR1 and SSR2, which are located in ORF1 and ORF2, respectively, affect the genetic reading frame, leading to protein products with altered sequences and computed structures. The ORF1 gene product is predicted to be a MAP surface protein with possible roles in host immune modulation, but nothing could be inferred regarding the function of ORF2. Both genes are conserved in Mycobacterium avium complex members, but SSR1-based modulation of ORF1 reading frames seems to only occur in MAP, which could have potential implications on the infectivity of this pathogen. IMPORTANCE Johne's disease (JD) is a major problem in dairy animals, and concerns have been raised regarding the association of Mycobacterium avium subsp. paratuberculosis (MAP) with Crohn's disease in humans. MAP is an extremely slow-growing bacterium with low genome evolutionary rates. Certain short sequence repeats (SSR1 and SSR2) in the MAP chromosome are highly variable and evolve at a faster rate than the rest of the chromosome. In the current study, multiple MAP isolates with genetic variations such as single-nucleotide polymorphisms, and more noticeably, diverse SSRs, could simultaneously infect animals. Variations in SSR1 and SSR2 affect the products of the respective genes containing them. Since multiple MAP isolates can infect the same animal and the possibility that the pathogen undergoes further changes within the host due to unstable SSRs, this could provide a compensative mechanism for an otherwise slow-evolving pathogen to increase phenotypic diversity for overcoming host responses.
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Affiliation(s)
- Alexander Byrne
- Department of Biology, Memorial University of Newfoundland, St. John’s, Newfoundland and Labrador, Canada
| | - Nathalie Bissonnette
- Sherbrooke Research and Development Centre, Agriculture and Agri-Food Canada, Sherbrooke, Quebec, Canada
| | - Séverine Ollier
- Sherbrooke Research and Development Centre, Agriculture and Agri-Food Canada, Sherbrooke, Quebec, Canada
| | - Kapil Tahlan
- Department of Biology, Memorial University of Newfoundland, St. John’s, Newfoundland and Labrador, Canada
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Falkinham JO. Nontuberculous mycobacteria in the environment. Tuberculosis (Edinb) 2022; 137:102267. [PMID: 36191391 DOI: 10.1016/j.tube.2022.102267] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2022] [Revised: 09/16/2022] [Accepted: 09/23/2022] [Indexed: 01/24/2023]
Abstract
The nontuberculous mycobacteria (NTM) are normal inhabitants of soils and waters and thereby surround humans due to their presence in water that is distributed to homes, apartments, offices, hospitals and long-term care facilities in pipes. The NTM are not contaminants of drinking water, rather they are colonists ideally adapted to growth and persistence in natural waters. Further those adaptations also favor NTM survival, persistence, and growth in drinking water systems. Thereby, NTM surround humans. The NTM love plumbing as it offers a high surface to volume ratio, ideal for surface adherence and biofilm formation. As a consequence, these slow growing bacteria are not flushed out by flowing water. Factors that support NTM growth and persistence in drinking water include: disinfectant-resistance, growth at low organic matter content (oligotrophic), surface attachment and biofilm formation, growth at low oxygen content (stagnant water), and desiccation-tolerance. A major determinant of the ecology of NTM is the lipid-rich outer membrane. The outer membrane provides a hydrophobic barrier that is relatively impermeable. Although the outer membrane reduces influx of nutrients, it also impedes transport of hydrophilic disinfectants (e.g., chlorine) and antibiotics. NTM are quite adaptable: able to grow in fresh or brackish natural waters and able to induce a high-temperature-resistant state.
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