Drug resistance of Mycobacterium tuberculosis.: Multicenter study in Barcelona, Spain

BACKGROUND: The aim of this multicenter study was to establish the level of primary and acquired drug resistance of M. tuberculosis strains isolated in Barcelona and to identify possible risk groups using clinical data. PATIENTS AND METHOD: All tuberculosis patients with isolation and identification of M. tuberculosis strains from October 1995 to September 1997 were included. Susceptibility tests against isoniazid, rifampin, ethambutol, streptomycin and pyrazinamide were performed using the Bactec 460 system and the proportions method on solid medium. Logistic progression was used for statistical analysis. RESULTS: The total number of patients included was 1,749 (1,535 non-treated and 214 previously treated). Primary drug resistance was 5.7% (isoniazid 3.8%; rifampin 1.0%, streptomycin 2.1%, ethambutol 0.3% and pyrazinamide 1.0%). Acquired drug resistance was 20.5% (isoniazid 17.3%; rifampin 9.8%, ethambutol 1.9%, streptomycin 4.7% and pyrazinamide 6.5%). Primary drug resistance against isoniazid and pyrazinamide were associated with foreign people. The total acquired drug resistance was associated with people over 60 years old and women. CONCLUSIONS: The low level of primary drug resistance enables antituberculosis treatment of non-treated patients to start with the standardised three-drug regimes except in the case of foreign people from countries with a high level of drug resistance. Susceptibility tests are recommended on all M. tuberculosis strains isolated, together with controlled studies of drug resistance surveillance.