RESUMEN
Although AIDS patients in other countries are frequently diagnosed as having atypical mycobacterial infection, in Southern Brazil there is a clinical impression that Mycobacterium tuberculosis is the rule rather than the exception. We made a retrospective review of cultures for mycobacteria at our hospital in order to determine the frequency of atypical mycobacteria and Mycobacterium tuberculosis in hospitalised patients in Porto Alegre, Brazil. Mycobacterium tuberculosis was the most frequent isolate (79.9 percent), regardless of HIV serostatus. Only 1.5 percent of the cultures yielded atypical mycobacteria, all of which in AIDS patients. Mycobacterium tuberculosis was diagnosed in most of the HIV-infected patients (81.2 percent). We conclude that Mycobacterium tuberculosis is frequent in both HIV infected and non-HIV infected patients in this part of the country