Transmission of tuberculosis in an endemic urban setting in Brazil

SETTING: Two out-patient facilities in Sao Paulo, Brazil. OBJECTIVE: To study the transmission pattern of tuberculosis (TB) among hum an immunodeficiency virus (HIV) infected and uninfected persons in a settin g endemic for TB. DESIGN: A prospective study comparing HIV-seropositive and -seronegative TB patients identified consecutively between 1 March 1995 and 1 April 1997, T he patients were stratified according to their Mycobacterium tuberculosis i solate IS6110 RFLP patterns. Risk factors were sought for infection with an RFLP cluster pattern strain, inferred to represent recent transmission. RESULTS: Fifty-eight (38%) of 151 HIV-seropositive patients and 36 (25%) of 142 HIV-seronegative patients were infected with M. tuberculosis isolates that belonged to cluster patterns (OR 1.84, 95%CI 1.08-3.13). Multi-drug-re sistant (MDR) strains were isolated from 19 patients, all of whom were HIV seropositive; 12 (63%) of these, and 46 (35%) of 132 drug-susceptible isola tes had cluster patterns (OR 3.20, 95%CI 1.08-9.77). CONCLUSION: In a TB-endemic urban setting in Brazil, the proportion of cast s resulting from recent transmission appears to be greater among HIV-seropo sitive than among HIV-seronegative patients. A large proportion of MDR-TB ( 63%) cases was caused by strains that had cluster RFLP patterns, suggesting recent transmission of already resistant organisms. This type of knowledge regarding TB transmission may help to improve locally appropriate TR contr ol programs.