As opposed to M. leprae and members of the M. tuberculosis complex, environmental opportunistic mycobacteria are normal inhabitants of municipal water and water aerosols⁽¹⁾. In addition, they may grow and replicate within protozoa like Acanthamoeba spp., which protect them from conventional water disinfection regimens. Their prevalence in municipal drinking water is directly related to their high innate resistance to chlorine and biocides⁽¹⁾. Systemic water treatment technologies such as ozone and chlorine have even been found to cause a shift in the population of waterborne microbial flora away from the original distribution to a greater predominance of members of the Actinomyces family, which includes Mycobacterium⁽²⁾.

Water is a likely source of M. avium complex infection in humans, as evidenced by a study in which DNA-based fingerprints of M. avium isolates from AIDS patients were found to be identical to those of isolates recovered from their drinking water⁽³⁾. Furthermore, environmental Mycobacteria such as M. fortuitum, M. chelonae, and M. avium are capable of forming biofilm, which enable their populations to persist in a water distribution system in spite of their slow doubling time, which can range from 2-48 hours⁽¹⁾.

Mycobacteria Facts:

• Mycobacteria possess an extraordinary ability to survive in tap water(4,5).
• Mycobacteria are tolerant of extreme temperatures⁽⁶⁾ and can therefore survive in both hot tap water and ice machines. The most thermoresistant species include M. avium complex, M. xenopi, M. phlei, and M. chelonae⁽¹⁾.
• M. avium exhibits higher chlorine resistance than other environmental mycobacteria, but even weaker mycobacterial species such as M. aurum are 100-fold more chlorine tolerant than E. coli^(7,8).
• They have a complex, lipid-rich cell wall that renders them hydrophobic. Their hydrophobicity assists in their attachment to the internal surfaces of plumbing systems, where they are thought to be biofilm formation “pioneers”⁽⁹⁾. It also causes them to migrate to the surface of an air-water interface, from which they are readily aerosolized⁽¹⁾.
• M. avium, M. fortuitum, and M. marinum have been shown to be amoeba resistant, namely able to survive phagocytosis by amoeba such as Acanthamoeba⁽¹⁰⁾. This characteristic has been linked to a higher degree of virulence and enhanced resistance to antimicrobial agents^(10,11). M. avium surviving within an amoeba have even been shown to survive the amoeba’s encystment in response to adverse environmental conditions and subsequent excystment when more favorable survival conditions emerged⁽¹²⁾.
• A definitive genetic link was established between M. mucogenicum isolates from a hospital shower and a bacteremic hospital patient⁽¹³⁾.
• A genetic link was established between M. simiae isolates found in a home shower and various hospital water sites to those found in patients who had contracted M. simiae pulmonary disease⁽¹⁴⁾.

References:
1. Primm, T.P., C.A. Lucero, and J.O. Falkinham III. 2004. Health impacts of environmental mycobacteria. Clin. Microbiol. Rev. 17(1): 98-106.
2. Norton, C.D., and M.W. LeChevallier. 2000. A pilot study of bacterial population changes through potable water treatment and distribution. Appl. Environ. Microbiol. 66:268-276.
3. von Reyn, C.F., J.N. Maslow, T.W. Barber, J.O. Falkinham III, and R.D. Arbeit. 1994. Persistent colonization of potable water as a source of Mycobacterium avium infection in AIDS. Lancet 343:1137-1141.
4. Nyka, W. 1974. Studies on the effect of starvation on mycobacteria. Infect. Immun. 9:843-850.
5. Smeulders, M.J., J. Keer, R.A. Speight, and H.D. Williams. 1999. Adaptaion of Mycobacterium smegmatis to stationary phase. J. Bacteriol. 181:270-283.
6. Schulze-Robbecke, R., and K. Buchholtz. 1992. Heat susceptibility of aquatic mycobacteria. Appl. Environ. Microbiol. 58:1869-1873.
7. Rehmann, K., N. Hertkorn, and A.A. Kettrup. 2001. Fluoranthene metabolism in Mycobacterium sp. strain KR20: identity of pathway intermediates during degradation and growth. Microbiology 147:2783-2794.
8. Le Dantec, C., J.P. Duguet, A. Montiel, N. Dumoutier, S. Dubrou, and V. Vincent. 2002. Chlorine disinfection and atypical mycobacteria isolated from a water distribution system. Appl. Environ. Microbiol. 68:1025-1032.
9. Hall-Stoodley, L., and H. Lappin-Scott. 1998. Biofilm formation by the rapidly growing mycobacterial species. FEMS Microbiol. Lett. 168:77-84.
10. Cirillo, J.D., S. Falkow, L.S. Tompkins, and L.E. Bermudez. 1997. Interaction of Mycobacterium avium with environmental amoebae enhances virulence. Infect. Immun. 65:3759-3767.
11. Miltner, E.C., and L.E. Bermudez. 2000. Mycobacterium avium grown in Acanthamoeba castellanii is protected from the effects of antimicrobials. Antimicrob. Agents Chemother. 44:1990-1994.
12. Steinert, M., K. Birkness, E. White, B. Fields, and F. Quinn. 1998. Mycobacterium avium bacilli grow saprozoically in coculture with Acanthamoeba polyphaga and survive within cyst walls. Appl. Environment. Microbiol. 64:2256-2261.
13. Kline, S., S. Cameron, A. Streifel, M.A. Yakrus, F. Kairis, K. Peacock, J. Besser, and R.C. Cooksey. 2004. An outbreak of bacteremias associated with Mycobacterium mucogenicum in a hospital water supply. Infect. Cont. Hosp. Epidemiol. 25:1042-1049.
14. Conger, N.G., R.J. O’Connell, V.L. Laurel, K.N. Olivier, E.A. Graviss, N. Williams-Boyer, Y. Zhang, B.A. Brown-Elliott, and R.J.Wallace, Jr. 2004. Mycobacterium simiae outbreak associated with a hospital water supply. Infect. Cont. Hosp. Epidemiol. 25:1050-1055.