No abstract

Eight water distribution systems were sampled over an 18-month period (528 water and 55 biofilm samples) to measure the frequency of recovery and number of mycobacteria, particularly Mycobacterium avium and Mycobacterium intracellulare, in raw source waters before and after treatment and within the distribution system. The systems were chosen to assess the influence of source water, treatment, and assimilable organic carbon levels on mycobacterial numbers. Overall, mycobacterial recovery from the systems was low (15% of samples). Numbers of mycobacteria ranged from 10 to 700,000 CFU liter ؊1 . The number of M. avium in raw waters was correlated with turbidity. Water treatment substantially reduced the number of mycobacteria in raw waters by 2 to 4 log units. Mycobacterial numbers were substantially higher in the distribution system samples (average, 25,000-fold) than in those collected immediately downstream from the treatment facilities, indicating that mycobacteria grow in the distribution system. The increase in mycobacterial numbers was correlated with assimilable organic carbon and biodegradable organic carbon levels (r 2 ‫؍‬ 0.65, P ‫؍‬ 0.03). Although M. intracellulare was seldom recovered from water samples, it was frequently recovered (six of eight systems) in high numbers from biofilms (average, 600 CFU/cm 2 ). Evidently, the ecological niches of M. avium and M. intracellulare are distinct.Members of the Mycobacterium avium complex (i.e., M. avium and Mycobacterium intracellulare) are environmental opportunistic human and animal pathogens (11,21,43). M. avium complex pulmonary infections are found in patients with predisposing lung conditions, such as silicosis and black lung (5, 43), and in patients with pulmonary alveolar proteinosis (42) and cystic fibrosis (23). Infections in elderly women without any of the known risk factors for M. avium complex infection have also been described (30). M. avium, but not M. intracellulare, infections are found in (and are limited to) the cervical lymph nodes of young children with erupting teeth (44). Immune deficiency resulting in AIDS (18) or due to interleukin-12 deficiency (1), malignancy (41), or immunosuppression associated with transplantation (33) is also a risk factor for M. avium complex infection. Infections in AIDS patients are disseminated (e.g., bacteremia [19]) and are almost entirely (i.e., 95%) due to M. avium, whereas both mycobacterial infections occur at equal frequencies in nonimmunodeficient patients with pulmonary disease (8, 17).One source of M. avium infection in AIDS patients is water. DNA fingerprints of M. avium isolates from water to which AIDS patients were exposed were identical to those of the patients (38). Further, the high incidence of M. avium infections in AIDS patients in Finland correlated with high numbers of M. avium in drinking and environmental waters (31). Water also appears to be the source of M. avium infections in simian immunodeficiency virus-infected macaques, based on the identity of DNA fingerprints of M. avium re...

SUMMARY Environmental mycobacteria are emerging pathogens causing opportunistic infections in humans and animals. The health impacts of human-mycobacterial interactions are complex and likely much broader than currently recognized. Environmental mycobacteria preferentially survive chlorination in municipal water, using it as a vector to infect humans. Widespread chlorination of water has likely selected more resistant environmental mycobacteria species and potentially explains the shift from M. scrofulaceum to M. avium as a cause of cervical lymphadenitis in children. Thus, human activities have affected mycobacterial ecology. While the slow growth and hydrophobicity of environmental mycobacteria appear to be disadvantages, the unique cell wall architecture also grants high biocide and antibiotic resistance, while hydrophobicity facilitates nutrient acquisition, biofilm formation, and spread by aerosolization. The remarkable stress tolerance of environmental mycobacteria is the major reason they are human pathogens. Environmental mycobacteria invade protozoans, exhibiting parasitic and symbiotic relationships. The molecular mechanisms of mycobacterial intracellular pathogenesis in animals likely evolved from similar mechanisms facilitating survival in protozoans. In addition to outright infection, environmental mycobacteria may also play a role in chronic bowl diseases, allergies, immunity to other pulmonary infections, and the efficacy of bacillus Calmette-Guerin vaccination.

Summary A majority of the Mycobacterium species, called the nontuberculous mycobacteria (NTM), are natural inhabitants of natural waters, engineered water systems, and soils. As a consequence of their ubiquitous distribution, humans are surrounded by these opportunistic pathogens. A cardinal feature of mycobacterial cells is the presence of a hydrophobic, lipid‐rich outer membrane. The hydrophobicity of NTM is a major determinant of aerosolization, surface adherence, biofilm‐formation, and disinfectant‐ and antibiotic resistance. The NTM are oligotrophs, able to grow at low carbon levels [>50 μg assimilable organic carbon (AOC) l−1], making them effective competitors in low nutrient, and disinfected environments (drinking water). Biofilm formation and oligotrophy lead to survival, persistence, and growth in drinking water distribution systems. In addition to their role as human and animal pathogens, the widespread distribution of NTM in the environment, coupled with their ability to degrade and metabolize a variety of complex hydrocarbons including pollutants, suggests that NTM may be agents of nutrient cycling.

No abstract

ABSTRACTThe spread of opportunistic pathogens via public water systems is of growing concern. The purpose of this study was to identify patterns of occurrence among three opportunistic pathogens (Legionella pneumophila,Mycobacterium avium, andPseudomonas aeruginosa) relative to biotic and abiotic factors in two representative chloraminated drinking water distribution systems using culture-independent methods. Generally, a high occurrence ofLegionella(≥69.0%) and mycobacteria (100%), lower occurrence ofL. pneumophila(≤20%) andM. avium(≤33.3%), and rare detection ofPseudomonas aeruginosa(≤13.3%) were observed in both systems according to quantitative PCR. Also,Hartmanella vermiformiswas more prevalent thanAcanthamoeba, both of which are known hosts for opportunistic pathogen amplification, the latter itself containing pathogenic members. Three-minute flushing served to distinguish distribution system water from plumbing in buildings (i.e., premise plumbing water) and resulted in reduced numbers of copies ofLegionella, mycobacteria,H. vermiformis, and 16S rRNA genes (P< 0.05) while yielding distinct terminal restriction fragment polymorphism (T-RFLP) profiles of 16S rRNA genes. Within certain subgroups of samples, some positive correlations, including correlations of numbers of mycobacteria and total bacteria (16S rRNA genes),H. vermiformisand total bacteria, mycobacteria andH. vermiformis, andLegionellaandH. vermiformis, were noted, emphasizing potential microbial ecological relationships. Overall, the results provide insight into factors that may aid in controlling opportunistic pathogen proliferation in real-world water systems.

To determine whether plumbing could be a source of nontuberculous mycobacteria (NTM) infection, during 2007–2009 I isolated NTM from samples from household water systems of NTM patients. Samples from 22/37 (59%) households and 109/394 (28%) total samples yielded NTM. Seventeen (46%) of the 37 households yielded >1 Mycobacterium spp. isolate of the same species as that found in the patient; in 7 of those households, the patient isolate and 1 plumbing isolate exhibited the same repetitive sequence-based PCR DNA fingerprint. Households with water heater temperatures <125°C (<50°C) were significantly more likely to harbor NTM compared with households with hot water temperatures >130°F (>55°C) (p = 0.0107). Although households with water from public or private water systems serving multiple households were more likely to have NTM (19/27, 70%) compared with households with a well providing water to only 1 household (5/12, 42%), that difference was not significant (p = 0.1532).

No abstract