Prospective study of drug-resistant tuberculosis in a Spanish urban population including patients at risk for HIV infection.

From January 1988 to October 1992, the primary resistance to first-line antituberculous drugs in 501 tuberculous patients was evaluated prospectively. Three-hundred and seventeen patients were HIV-negative and 184 were HIV-positive; these patients had several different clinical forms of tuberculosis. Moreover, the acquired resistance to antituberculous drugs was studied in 295 non-AIDS patients and in 42 AIDS patients with evidence of antecedent tuberculosis treatment. The data indicated that during these five years there was no consistent and clear-cut trend toward greater frequency of primary drug resistance to any of the first-line antituberculous drugs. Primary drug resistance in HIV-positive patients (7.1%) did not differ significantly (p > 0.05) from that found in HIV-negative patients (8.2%). Among HIV-positive patients, the acquired drug resistance pattern was similar to that detected in HIV-negative patients although the frequency of resistance in the former (69%) was significantly higher (p < 0.01). During the study, resistance to isoniazid was almost constant in the acquired-resistance cases and was frequently associated with resistance to other drugs. Furthermore, the acquired resistance to isoniazid was often of a higher level (1 to 10 mg/l) than the primary resistance (0.2 mg/l), and those strains were usually catalase and peroxidase negative.