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

BACKGROUND: Drug resistance threatens global tuberculosis (TB) control efforts. Population-based estimates of drug resistance are needed to develop strategies for controlling drug-resistant TB in Mexico.
OBJECTIVE: To obtain population-based data on Mycobacterium tuberculosis drug resistance in Mexico.
METHODS: To obtain drug resistance data, we conducted a population-based study of TB cases in the states of Baja California, Sinaloa, and Oaxaca, Mexico. 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 significantly more likely than new cases to have isolates resistant to 1 or more of the 3 first-line drugs (relative risk [RR], 3.9; 95% confidence interval [CI], 2.8-5.5), to have isoniazid resistance (RR, 3.6; 95% CI, 2.5-5.2), and to have multi-drug-resistant TB (RR, 9.4; 95% CI, 4.3-20.2).
CONCLUSIONS: This population-based study of M tuberculosis demonstrates moderately high levels of drug resistance. Important issues to consider in the national strategy to prevent M tuberculosis resistance in Mexico include consideration of the most appropriate initial therapy in patients with TB, the treatment of patients with multiple drug resistance, and surveillance or periodic surveys of resistance among new TB patients to monitor drug resistance trends.