Effects of antimicrobial agents on survival of Mycobacterium avium complex inside alveolar macrophages obtained from patients with human immunodeficiency virus infection.

Measurements of the activities of antimicrobial agents against the Mycobacterium avium complex (MAC) usually do not take into consideration the intracellular location of the organism. A recent study using mouse macrophage continuous cell line J774 (D. M. Yajko, P.S. Nassos, C. A. Sanders, and W. K. Hadley, Am. Rev. Respir. Dis. 140: 1198-1203, 1989) showed that certain combinations of antimicrobial agents are able to kill MAC inside macrophages and suggested that the J774 cell line could be used as a model for screening of drugs for intracellular activity against MAC. As a test of the validity of this model, alveolar macrophages were isolated from the bronchoalveolar lavages of 36 patients who had AIDS or an AIDS-related condition or were considered to be at risk for AIDS. The macrophages were infected with MAC and then treated with a drug or drug combination for 48 to 72 h. Survival of MAC was measured over time in drug-treated macrophages and untreated control macrophages. No single drug or two-drug combination that was tested was able to cause a decrease in the survival of every one of the MAC strains used in the study. However, several three-drug combinations that had been shown to cause a decrease in survival of all MAC strains inside J774 cells also caused a decrease in survival of all MAC strains inside alveolar macrophages from patients. The good agreement between these results and those obtained previously with J774 cells gives further evidence of the usefulness of the simpler J774 model for screening of drugs for intracellular activity against MAC.