Primary and acquired resistance of Mycobacterium tuberculosis in Western Mexico.

Resistance of Mycobacterium tuberculosis to antimycobacterial agents is a worldwide problem. The proposite of this study was to analyze the current resistance patterns of patients with initial episodes, as well as relapses, due to M. tuberculosis in western Mexico. From January 1993 to February 1999 a total of 237 strains of M. tuberculosis (120 from initial cases and 117 from relapse cases) were analyzed. Two hundred and four (86%) strains were isolated from the lower respiratory tract, and 33 strains (14%) from extrapulmonary sites. Twenty-three percent of M. tuberculosis isolated from patients with initial episodes were resistant to both isoniazid and rifampin, and 52% of M. tuberculosis isolated from relapse cases were also resistant to both isoniazid and rifampin.