Factors Influencing Numbers of Mycobacterium avium , Mycobacterium intracellulare , and Other Mycobacteria in Drinking Water Distribution Systems

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...

Opportunistic pathogens enriched in showerhead biofilms

“…Mycobacteria readily form biofilms and, because of their generally waxy quality, may be particularly resistant to shear forces generated in shower operation (28)(29)(30)(31)(32)(33)(34)(35)(36). Furthermore, many species of biofilm-forming mycobacteria are chlorineresistant, and thus potentially can be enriched by chlorine disinfection protocols used by many municipalities (28,29,34,37,38). Consistent with this, we only observed mycobacterial rRNA gene sequences in municipal water systems, not in untreated well water systems.…”

Molecular identification of potential pathogens in water and air of a hospital therapy pool

“…We anticipated that mycobacteria might occur in biofilms growing on containment surfaces because of their documented occurrence in chlorinated water pipes and other drinking water appurtenances (27,28). Indeed, we observed enrichment of mycobacteria in biofilms compared with pool water (Fig.…”

Microbiological problems and biofilms associated with Mycobacterium chimaera in heater–cooler units used for cardiopulmonary bypass

“…Both M. avium and M. intracellulare are recovered more frequently from pipe surfaces in biofilms, than in the planktonic phase 65,66 . However, M. intracellulare forms biofilms more readily than the less hydrophobic M. avium, which is more commonly found in the bulk water 65,67 Despite the global distribution and use of 3T HCUs, whole genome analysis has demonstrated a lack of genetic diversity between isolates 2, 4 . In Australia, M. chimaera was recovered from 10 HCUs across four different hospitals 2 .…”