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. |