Epidemiology of Mycobacterium avium complex infecting AIDS patients

Organisms of the Mycobacterium avium complex cause disseminated infections in 25 to 50 % of patients with AIDS. To assess the likelihood of exposure to M avium, we attempted to recover M. avium complex from environmental samples in geographical areas (Boston, Massachusetts; Hanover, New Hampshire; Helsinki, Finland; Nairobi, Kenya; and Kinsasha, Zaire) located near M. avium infected AIDS patients. Although M. avium was recovered from environmental samples at all sites, it was found more frequently in water supply systems in the United States and Finland (8/25, 32 %) compared to water supply samples from Africa (0/14, 0%).

To determine if M. avium isolates recovered from the same geographical area as AIDS patients shared phenotypic and genetic characteristics with clinical AIDS M. avium isolates (recovered by collaborating laboratories), the ability to grow at 43°C, cadmium-and streptomycin-resistance, and the presence of plasmids were used as epidemiological markers. We found that environmental isolates in this study shared similar characteristics with the clinical AIDS M. avium isolates.

Compared to developed countries, the prevalence of M. avium infections among AIDS patients in developing countries (i.e., Africa) is very low. To determine if M. avium was absent in the African environment, we attempted to recover the organisms from water and soil in Kampala, Uganda. M. avium was recovered from 43 % of environmental samples, and these isolates shared similar phenotypic and genetic characteristics with M. avium isolates from the United States.

Cigararette smoking was identified as a possible risk factor for HIV infected individuals. M avium isolates were recovered from several brands of cigarettes, suggesting that cigarettes are a possible source of infection.