Resistance patterns of patients with initial episodes and relapses due to M. tuberculosis and nontuberculous mycobacteria

Background: A recognized risk factor for drug resistance include previous treatment for tuberculosis. We report the current resistance patterns of patients with initial episodes as well as from relapses in Mexico's west. Objetive: To evaluate the resistance patterns of patients with initial episodes and relapses due to mycobacterial species. Methods: Since January 1992 all patients with a positive culture were analyzed, as initial or relapses cases. Susceptibility tests were done by the Canetti method. Results: 211 positive cultures from 189 patients were found. 132 from patients with an initial episode and 79 with relapses. Species isolated were: M. tuberculosis 126, M. avium-intraceilulare 20, M, bovis 19, M. triviale 14, M. gordonae 5, and others 31. Nontuberculous mycobacteria was isolated in 50% of patients with initial episodes and in 24 % of patients with relapses. Pulmonary location was seen in 70% of patients with initial episodes and in 86% in patients with relapses. 27% of Mycobaclerium tuberculosis and 48% of nontuberculous mycobacteria isolated from patients with initial episodes were resistant to isoniazid and rifampin. 60% of M. tuberculosis and 50% of nontuberculous mycobacteria isolated from relapses were resistant to isoniazid and rifampin. Conclusions: Extrapulmonary location and nontuberculous mycobacteria etiology are most common in patients with initial episodes. M. tuberculosis isolated from patients with initial episodes tend to be more sensitive than other