Azithromycin prophylaxis for Mycobacterium avium complex during the era of highly active antiretroviral therapy: evaluation of a provincial program.

Mycobacterium avium complex (MAC) disease was evaluated in a provincial program of azithromycin prophylaxis. Highly active antiretroviral therapy (HAART) was prescribed to 383 (65%) of 587 patients eligible for MAC prophylaxis (CD4 <75 cells/mm3). By use of an intent-to-treat analysis, MAC disease was observed in 21 of 271 patients who did not receive prophylaxis (incidence rate, 8 events per 100 person-years). MAC events occurred in 10 of 316 patients who received azithromycin (2.37 events per 100 person-years). Localized lymphadenitis compatible with immune reconstitution disease accounted for 23% of all MAC events, in contrast to studies in the pre-HAART era, where almost all cases were disseminated. None of the MAC isolates from the 10 prophylaxis failures were resistant to azithromycin. Azithromycin appeared to be protective against disseminated MAC in patients who were either unresponsive or nonadherent to HAART, but it did not prevent the development of immune reconstitution disease due to MAC.