Micobacterium Avium
White Paper 01/02/2000
The Environmental Protection Agency (EPA) has promulgated a variety of water quality regulations aimed at reducing microbial risk associated with drinking water. These include the Surface Water Treatment Rule and the Total Coliform Rule. Much of the current regulatory efforts are focused on protozoans such as Giardia and Cryptosporidium and viruses which typically cause gastrointestinal disease originate in source waters in contrast to the limited attention to opportunistic bacterial pathogens (e.g., Legionella, Helicobacter, etc.) which can grow in distribution systems.
Recently, interest in opportunistic pathogens has also been stimulated by special risks to those with immune compromising conditions and the movement towards the use of an alternative to chlorine for disinfection and the concern that increases in biodegradable organic matter will stimulate growth of bacteria in the distribution system. This paper summarizes relevant information and current research issues on the public health significance of Mycobacterium Avium Complex (MAC) in particular regard to the presence of MAC in municipal water systems.
Mycobacterium Avium Complex (MAC) is a family of opportunistic bacterial pathogens related to mycobacterium tuberculosis that are found almost everywhere in our environment, including food, water and soil. Some types of MAC bacteria cause disease, primarily in individuals with compromised immune systems but also rarely in individuals without identified susceptibilities.
The prevalence of MAC disease was 1.1 per 100,000 in the pre- AIDS era and these cases were most often recognized in persons with underlying lung disease. Potentially, water is a route of exposure to MAC through ingestion and inhalation of aerosols. However, given a lifetime of exposure to a ubiquitous agent and the limited number of individuals with recognized disease, the lifetime risk from Mycobacterium Avium Complex (MAC) for the normal immunocompetent host is very small.
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