Disseminated Mycobacterium genavense infection in Canadian AIDS patients

Mycobacterium genavense is a recently described mycobacterial species which thus far has been identified only in persons with advanced HIV disease. It appears to be a rare pathogen with an undefined reservoir. We describe the first two cases of M. genavense infection in Canadian AIDS patients. The clinical presentation of fever and wasting with extremely low CD4 lymphocyte counts was indistinguishable from disseminated M. avium complex (MAC) infection. However, blood cultures in BACTEC 13A medium required a mean of 58 days (range 41-87) to detect growth of M. genavense in contrast to a mean of 10 days for MAC in our laboratory. M. genavense infection is underdiagnosed due to the lack of universal use of BACTEC liquid medium and the use of relatively short incubation times (only 6 weeks) by some laboratories. The value of antimycobacterial therapy for M. genavense is unknown, but anecdotal data suggest that treatment with a regimen appropriate for MAC may be beneficial.