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.
PIP: The survey was conducted in Argentina, Bolivia, Brazil, Chile, Colombia, Cuba, Haiti, Mexico, Paraguay, and Peru. 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 who presumably had never previously been treated for tuberculosis were collected from 30 randomly selected clusters in Latin America and tested for resistance to isoniazid (H), streptomycin (SM), rifampicin (R), ethambutol (E), and thiacetazone (Th). Unevenly distributed, initial drug resistance was detected in all the clusters tested and characterized one out of every six tuberculosis cases. A total of 159 of the 948 clusters tested (16.8%) exhibited some type of drug resistance, ranging from 2.7% to 54.5. Resistance to one drug was 12.2%, to two drugs was 3.4%, and to more than two drugs was 1.2%. A total of 116 (12.2%) strains exhibited single-drug resistance: H-26 strains from all 10 countries; SM-70 strains also from all 10 countries; Th-16 strains from Colombia, Cuba, Mexico, Paraguay, and Peru; and R-four strains from Colombia, Mexico, and Peru. Another 32 (3.3%) strains exhibited simultaneous resistance to two drugs, distributed as follows: H-SM: 25 strains (2.6%) from Argentina, Bolivia, Brazil, Chile, Colombia, Mexico and Peru; SM-Th: five strains (0.5%) from Colombia and Peru; R-E: one strain (0.1%) from Haiti; and H-R: one strain (0.1%) from Peru. Another 10 (0.1%) strains exhibited simultaneous resistance to three drugs: H-SM-Th: four strains (0.4%), from Bolivia, Brazil, Cuba, and Peru; H-SM-R: three strains (0.3%) from Peru; H-SM-E: two strains, one from Mexico and one from Peru; and H-E-Th: one strain (0.1%) from Cuba. Finally, one strain (0.1%) from Brazil exhibited resistance to four drugs: H-SM-R-Th. The total resistance was as follows: H (6.5%); SM (11.6%); R (1.1%); E (0.4%); and Th (2.6%).