Mycobacterium

(endorsed 2011)

Guideline

No guideline value has been set for Mycobacterium spp. in drinking water and its inclusion in routine monitoring programs is not recommended.

A multiple barrier approach from catchment to tap is recommended to minimise the risk of contamination. Minimising biofilm growth and maintaining cleanliness of distribution systems is a priority. Operation of barriers should be monitored to ensure effectiveness and that microbial health-based targets are being met.

General description

Mycobacteria are saprophytic, aerobic, rod-shaped and acid-fast bacteria. The “typical” species M. tuberculosis, M. bovis, M. africanum and M. leprae, which are associated with diseases such as tuberculosis and leprosy, have only human or animal reservoirs and are not transmitted by water. In contrast, the non-tuberculous or “atypical” species of Mycobacterium grow slowly in a variety of water environments including biofilms. One of the most commonly occurring atypical species, M. gordonae, is known as the “tap water bacillus”. Other species associated with water include M. avium, M. intracellulare, M. kansasii, M. marinum, M. scrofulaceum, M. xenopi and the (relatively) more rapid growers M. chelonae and M. fortuitum. The term “M. avium complex” has been used to describe a group of pathogenic species including M. avium and M. intracellulare. However, other atypical mycobacteria are also pathogenic.

Principal routes of infection are inhalation, contact, and ingestion of contaminated water. Infection by various species has been associated with their presence in drinking water supplies. Aerosols generated from showerheads were linked to M. kansasii infections in the Czech Republic (Chobot et al. 1997). Infection by other species has been associated with contaminated water in spas and ice machines (Lumb et al. 2004, Pedley et al. 2004).

The ecology of environmental Mycobacterium spp. is poorly understood; however, there is increasing evidence that they can survive and grow in water distribution systems. In a similar fashion to Legionella, resistance to disinfection is enhanced by the ability of mycobacteria to survive intracellularly within amoebae and to grow in biofilms (Pedley et al. 2004). In water distribution systems, the presence of mycobacteria has been associated with increased turbidity, dissolved organic carbon and biofilms (Falkinham et al. 2001, Pedley et al. 2004).

Australian significance

An Australian survey in 2000 provided a conservative estimate of 1.8 infections with atypical mycobacteria per 100,000 people (Haverkort 2003). Many of the infections were asymptomatic, with the most common sites of disease being the respiratory tract, soft tissue and the lymphatic system. It is considered that most infections arise from environmental exposure, although sources are typically not identified. Water was a possible source of M. kansasii infection in Portland, Victoria (Huang et al. 1991) and infections were linked to spa pools in Adelaide (Lumb et al. 2004).

Preventing contamination of drinking water

Mycobacterium spp. are relatively resistant to treatment and disinfection (LeChevallier 2004) and this is exacerbated by growth in biofilms. Control measures that are designed to minimize biofilm growth, including removal of organic carbon, restriction of residence times of water in distribution systems and maintenance of disinfectant residuals, should reduce growth of these organisms.

Method of identification and detection

Mycobacterium spp. have a high lipid content in cell walls, which enables them to retain specific dyes in staining procedures that employ an acid wash (i.e., acid-fast). Most of the Mycobacterium spp. including the “M. avium complex” are characterised by slow growth, with optimum generation times ranging from 2 to 48 hours. The rapid-growing species (e.g. M. chelonae and M. fortuitum ) can be detected after 5 days. Concentration and culture methods are available, but the slow growth of mycobacteria adds to the difficulty of growth and identification. DNA and antibody-based methods are also available (Stinear et al. 2004).

Health considerations

Atypical Mycobacterium spp. can cause a range of diseases involving the skeleton, lymph nodes, skin and soft tissues, as well as the respiratory, gastrointestinal and genitourinary tracts. Manifestations include pulmonary disease, skin ulcers (e.g., Buruli and Bairnsdale ulcers), osteomyelitis and septic arthritis in people with no known predisposing factors. Mycobacteria are a major cause of disseminated infections in people who are immunocompromised and are a common cause of death in people who are HIV-positive.

Derivation of guideline

No guideline value is proposed for Mycobacterium spp. and inclusion in routine verification monitoring programs is not recommended. The focus should be on monitoring of control measures designed to minimize biofilm growth, and monitoring the cleanliness of distribution systems.

References

Chobot S, Malis J, Sebakova H, Pelikan M, Zatloukal O, Palicka P, Kocurova D (1997). Endemic incidence of infections caused by Mycobacterium kansasii in the Karvina district in 1968-1995. Central European Journal of Public Health, 5(4):164-173.

Falkinham JO, Norton CD, LeChevallier MW (2001). Factors influencing numbers of Mycobacterium avium, Mycobacterium intracellulare and other mycobacteria in drinking water distribution systems. Applied and Environmental Microbiology, 66:1225-1231.

Havekort F (2003). National atypical mycobacteria survey, 2000. Communicable Disease Intelligence, 27(2):180-189.

Huang ZH, Ross BC, Dwyer B (1991). Identification of Mycobacterium kansasii by DNA hybridization. Journal of Clinical Microbiology, 29:2125-2129.

LeChevallier MW (2004). Control, treatment and disinfection of Mycobacterium avium complex in drinking water. In: Pedley S, Bartram J, Rees G, Dufour A, Cutruvo JA (eds), Pathogenic Mycobacteria in Water: A guide to public health consequences, monitoring and management. World Health Organization, Geneva, pp 143-168.

Lumb R, Stapledon R, Scroop A, Bond P, Cunliffe D, Goodwin A, Doyle R, Bastian I (2004). Investigation of spa pools associated with lung disorders caused by Mycobacterium avium complex in immunocompetent adults. Applied and Environmental Microbiology, 70:4906-4910.

Pedley S, Bartram J, Rees G, Dufour A, Cutruvo JA (eds) (2004). Pathogenic Mycobacteria in Water: A guide to public health consequences, monitoring and management. World Health Organization, Geneva, Switzerland.

Stinear T, Ford T, Vincent V (2004). Analytical methods for the detection of waterborne and environmental pathogenic mycobacteria. In: Pedley S, Bartram J, Rees G, Dufour A, Cutruvo JA (eds), Pathogenic mycobacteria in water: A guide to public health consequences, monitoring and management. Geneva, World Health Organization, pp 55-73.