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Mycobacterium avium complex (MAC) infections in HIV-infected patients

Judith S Currier, MD
Section Editor
John G Bartlett, MD
Deputy Editor
Jennifer Mitty, MD, MPH


Mycobacterium avium complex (MAC) refers to infections caused by one of two nontuberculous mycobacterial species, either M. avium or M. intracellulare. Infection with these organisms can occur in patients with or without HIV infection. The two principal forms of MAC infection in patients with HIV are disseminated disease and focal lymphadenitis. By contrast, isolated pulmonary infection is typically seen in immunocompetent patients.

Among HIV-infected patients, MAC infection is most commonly seen among those with a CD4 count <50 cells/microL. Dramatic declines in the rate of new MAC cases accompanied the use of prophylaxis against MAC infection early in the epidemic, and more recently, the widespread use of effective antiretroviral therapy [1-3].

The epidemiology, clinical manifestations, diagnosis, treatment, and prevention of MAC infection in HIV disease will be reviewed here. MAC infections in patients without HIV are discussed separately. (See "Microbiology of nontuberculous mycobacteria" and "Overview of nontuberculous mycobacterial infections in HIV-negative patients" and "Treatment of Mycobacterium avium complex lung infection in adults".)


Transmission — The mode of infection for Mycobacterium avium complex (MAC) is thought to be through inhalation or ingestion. MAC organisms are ubiquitous in the environment, including water and soil [4]. (See "Epidemiology of nontuberculous mycobacterial infections", section on 'Mycobacterium avium complex'.)

There is no need for isolation of hospitalized patients with MAC infection since person-to-person or common source transmission of MAC appears to be rare. In one report that evaluated 32 patients with AIDS and MAC from a daycare center in France over a 13-month period, the strains of organisms were heterogeneous by pulsed-field gel electrophoresis [5]. Another series of 130 isolates from children, both HIV-infected and not infected, also failed to show a clonal origin for the strains, although HIV-infected children were more commonly infected with M. avium than controls (88 versus 38 percent) [6].

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Literature review current through: Nov 2017. | This topic last updated: May 31, 2017.
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