Mycobacteria and AIDS

Mycobacteria are acid-fast, slow-growing microorganisms which have gained attention due to increasing prevalence in AIDS patients. Until the advent of AIDS, the only true pathogens of this group were Mycobacterium tuberculosis and M. leprae and the remaining mycobacteria were considered to be saprophytes or opportunistic pathogens. Infection with the MOTT (mycobacteria other than tuberculosis) bacilli was only seen in elderly or immunocompromised patients and was generally limited to caseating pulmonary granulomas, with rare extrapulmonary involvement. In AIDS patients, however, the incidence of mycobacterial infections ranges from 10 to 60% of HIV-positive persons, depending on location, method of identification, and patient population. Furthermore the pathogenesis of these mycobacterioses is distinct from that seen in non-AIDS patients because disseminated disease is the rule rather than the exception. Finally treatment of mycobacterial infections is increasingly difficult due to multiple drug resistances as well as the length of antimicrobial therapy required to cure the disease. Because of the prevalence and importance of these microorganisms, much research has been performed with the mycobacteria to develop new therapies and to understand their modes of pathogenesis.