Controversies in the management of Mycobacterium avium complex infection in AIDS patients

Abstract

Objective: To update readers on the clinical management of infections secondary to Mycobacterium avium complex (MAC) in patients with AIDS. A general description of the organism, culture and susceptibility testing, and clinical manifestations of the disease is provided. Several aspects of the treatment of the disease, including an historical perspective, current approaches, and future research opportunities, are described.

Data sources: Current medical literature, including abstracts presented at international meetings, is reviewed. References were identified through MEDLINE, Current Contents, and published meeting abstracts.

Study selection: Data regarding the epidemiology, clinical manifestations, culture and susceptibility testing, and treatment of MAC are cited. Specific attention is given to the management of patients with MAC infection.

Data extraction: Information contributing to the discussion of the topics selected by the author is reviewed. Data supporting and disputing specific conclusions are presented.

Data synthesis: Disseminated MAC infection is diagnosed antemortem in approximately 30 percent of patients with AIDS; postmortem rates of isolation exceed 50 percent. The incidence of MAC may increase as attempts at isolating the organism become more aggressive. The traditional approach to the isolation, susceptibility testing, and treatment of MAC has been derived from the management of Mycobacterium tuberculosis, with disappointing results. Newer radiometric in vitro methods of susceptibility testing appear to show more promise. Current mouse models of MAC are not true AIDS models; new CD4-deficient mouse models are being developed. Clinical mycobacteriologic and pharmacokinetic laboratory support have been underused, with treatment generally proceeding empirically. New agents that may contribute to the management of disseminated MAC infection include the macrolide derivatives clarithromycin and azithromycin. Research also continues with new rifamycins (including rifabutin) and fluoroquinolones (ciprofloxacin, sparfloxacin). Preliminary results suggest a central role for macrolides in the treatment of disseminated MAC; effective companion drugs are needed to prevent the rapid emergence of macrolide-resistant MAC.

Conclusions: Treatment results for disseminated MAC infection remain poor. Therapy may be improved by selecting drugs on the basis of susceptibility data for each isolate, rather than by using empiric regimens based on susceptibility trends. Significant antimycobacterial drug malabsorption has been documented, and may contribute to poor outcomes. More-potent agents are needed to improve the clinical outcome in AIDS patients with MAC.