Survey of drug resistance of Mycobacterium tuberculosis in 3 Mexican states, 1997

Background: Drug resistance threatens global tuberculosis (TB) control effo rts. Population-based estimates of drug resistance are needed to develop st rategies for controlling drug-resistant TB in Mexico. Objective: To obtain population-based data on Mycobacterium tuberculosis dr ug resistance in Mexico. Methods: To obtain drug resistance data, we conducted a population-based st udy of TB cases in the states of Baja California, Sinaloa, and Oaxaca, Mexi co. We performed cultures and drug susceptibility testing on M tuberculosis isolates from patients with newly diagnosed, smear-positive TB from April 1 to October 31, 1997. Results: Mycobacterium tuberculosis was isolated from 460 (75%) of the 614 patients. Levels of resistance in new and retreatment TB cases to 1 or more of the 3 current first-line drugs used in Mexico (isoniazid, rifampin, and pyrazinamide) were 12.9% and 50.5%, respectively; the corresponding levels of multi-drug-resistant TB were 2.4% and 22.4%. Retreatment cases were sig nificantly more likely than new cases to have isolates resistant to 1 or mo re of the 3 first-line drugs (relative risk [RR], 3.9; 95% confidence inter val ICI], 2.8-5.5), to have isoniazid resistance (RR, 3.6; 95% CI, 2.5-5.2) , and to have multidrug-resistant TB (RR, 9.4; 95% CI, 4.3-20.2). Conclusions: This population-based study of M tuberculosis demonstrates mod erately high levels of drug resistance. Important issues to consider in the national strategy to prevent M tuberculosis resistance in Mexico include c onsideration of the most appropriate initial therapy in patients with TB, t he treatment of patients with multiple drug resistance, and surveillance or periodic surveys of resistance among new TB patients to monitor drug resis tance trends.