Preventing disseminated Mycobacterium avium complex disease in patients infected with human immunodeficiency virus.

Disseminated Mycobacterium avium complex (MAC) infection is an important late-stage complication of infection with the human immunodeficiency virus. Since MAC is widely dispersed in the environment, the source of infection for patients with disseminated MAC generally cannot be determined. Therefore, specific recommendations for avoiding exposure are not supported at this time. Routine screening of stools and sputum to detect MAC colonization as a means of targeting prophylaxis for disseminated disease is also not recommended at present. Two randomized, placebo-controlled trials have demonstrated that prophylactic use of rifabutin in persons with low CD4 lymphocyte counts results in a 50% decrease in MAC bacteremia as well as a reduction in some signs, symptoms, and laboratory abnormalities associated with MAC disease. Thus a prophylactic daily dose of rifabutin (300 mg) should be considered for adults who have had a previous AIDS-defining opportunistic illness and who have a CD4 lymphocyte count of < 75/microL. Many experts would consider prophylaxis appropriate only when the CD4 lymphocyte count is < 50/microL, particularly when there has not been a previous AIDS-defining opportunistic infection. Clinicians should be aware of drug interactions and potential adverse effects associated with the use of rifabutin. Preliminary reports of randomized, placebo-controlled trials suggest that chemoprophylaxis with clarithromycin is also effective in the prevention of disseminated MAC disease, and evaluation of other agents is under way. Prophylaxis for disseminated MAC infection in children has not been evaluated but is presumed to be as effective as that in adults. Decisions regarding initiation of MAC chemoprophylaxis should be individualized.