A random sample survey of initial drug resistance among tuberculosis cases in Latin America.

A random sample survey of initial drug resistance among cases of tuberculosis in Latin America was carried out during the second half of the 1980s and the early 1990s. A total of 948 cultures of Mycobacterium tuberculosis isolated from patients presumed never before to have been treated for tuberculosis were collected from 30 randomly selected clusters in Latin America and tested for resistance to isoniazid, streptomycin, rifampicin, ethambutol, and thioacetazone. Initial drug resistance, although unevenly distributed, was detected in all the clusters tested and characterized one out of every six tuberculosis cases. Both single and multiple resistance to streptomycin and to isoniazid were the most prevalent forms throughout the region but were not sufficiently frequent to jeopardize significantly the outcome of short-course chemotherapy. However, localized pockets of high drug resistance occurred throughout the region and are cause for concern, especially in the case of rifampicin.