Background: Since the appearance of AIDS, bacteremia by Mycobacterium tuberculosis is an event described with ever greater frequency. The isolation of M. tuberculosis in blood cultures in patients coinfected by the human immunodeficiency virus and M. tuberculosis may vary the initial clinical diagnosis and confirm the picture as disseminated tuberculosis.
Methods: The clinical records of patients admitted to the General Penitentiary Hospital of Madrid with significant bacteremia during the study period (March 1, 1991-September 1992) were retrospectively and prospectively reviewed. Special attention was given to the bacteremias by M. tuberculosis with the most significant clinical evolutive data being collected. The blood cultures were performed according to the routine technique using a non radiometric system with 10-day incubation and posterior processing of the sample for visualization and culture for mycobacteria.
Results: In an 18 moth period and out of a total of 284 positive blood cultures (154 significant isolations) 14 episodes of bacteremia by M. tuberculosis were studied in 12 prison patients coinfected by the human immunodeficiency virus with associated severe immunosuppression (mean of CD4 = 0.068 x 10(9)/l). All the patients were intravenous drug addicts. Likewise, 37 other significant bacteremias were reviewed. The positivity of the blood culture as the sole sample or associated to respiratory isolations, changed the initial diagnosis and classified the picture as disseminated tuberculosis on 6 occasions (43%). All the patients presented pictures of disseminated tuberculosis although only four had been previously diagnosed of AIDS.
Conclusions: Bacteremia by M. tuberculosis is frequent in patients infected by the human immunodeficiency virus. M. tuberculosis (27.4%) was the most frequently isolated microorganism in blood cultures in this study. The processing of blood cultures for mycobacteria may be useful in patients positive for the human immunodeficiency virus with tuberculosis in order to confirm the diagnosis of disseminated tuberculosis. The isolation of M. tuberculosis in the blood may vary the initial diagnosis and could modify the prevalence of AIDS cases in Spain.