The international epidemiology of disseminated Mycobacterium avium complex infection in AIDS. International MAC Study Group.

OBJECTIVE: To determine rates of disseminated Mycobacterium avium complex (MAC) infection among AIDS patients in developed and developing countries, and to determine whether different rates reflect differences in exposure or immunity, or both. DESIGN: Prospective cohort study. SETTING: University hospitals and outpatient AIDS programs. METHODS: HIV-infected subjects with CD4 counts < 200 x 10(6)/l were interviewed and had CD4 lymphocyte counts, blood cultures for mycobacteria (baseline and at 6 months), and skin tests with purified protein derivative (PPD) and M. avium sensitin. RESULTS: Among 566 study patients rates of disseminated MAC were 10.5-21.6% in New Hampshire, Boston and Finland compared to 2.4-2.6% in Trinidad and Kenya (P < 0.001). PPD skin test reactions > or = 5 mm were present in 20% of patients from Kenya compared to 1% at other sites (P < 0.001). Among patients from the United States and Finland, multiple logistic regression indicated that occupational exposure to soil and water was associated with a decreased risk of disseminated MAC, whereas the following were associated with an increased risk of disseminated MAC: low CD4 count, swimming in an indoor pool, history of bronchoscopy, regular consumption of raw or partially cooked fish/shellfish and treatment with granulocyte colony-stimulating factor. CONCLUSIONS: Rates of disseminated MAC in AIDS are higher in developed than developing countries and are due to both differences in exposure and differences in immunity. These data provide a rationale for prevention of MAC through both active immunization and reduction in exposure to the organism.

Evidence of previous infection with Mycobacterium avium-Mycobacterium intracellulare complex among healthy subjects: an international study of dominant mycobacterial skin test reactions.

Skin tests with 0.1 mL of intermediate-strength Mycobacterium tuberculosis purified protein derivative (PPD) and 0.1 mL of Mycobacterium avium sensitin were conducted on 484 healthy subjects from diverse geographic sites. Reactions of > or = 5 mm to one antigen that exceeded the reaction to the other by > or = 3 mm were considered M. avium- or PPD-dominant. PPD-dominant reactions were more frequent at sites where routine Bacille Calmette-Guérin immunization is done or where there are high rates of tuberculosis: New Hampshire, 2%; Boston, 7%; Finland, 14%; Trinidad, 26%; and Kenya, 28%. However, rates of M. avium-dominant reactions ranged from 7% to 12% at all sites. Analysis of dominant reactions based on a more stringent 10-mm minimum reaction size showed similar trends. These data suggest that exposure to MAC is similar in developed and developing countries but that broad mycobacterial immunity is greater in developing countries and may contribute to the lower rates of disseminated MAC infections in AIDS in these areas.