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 i n Barcelona and to identify possible risk groups using clinical data. PATIENTS AND METHOD: All tuberculosis patients with isolation and identific ation of M. tuberculosis strains from October 1995 to September 1997 were i ncluded. Susceptibility tests against isoniazid, rifampin, ethambutol, stre ptomycin and pyrazinamide were performed using the Bactec 460 system and th e proportions method on solid medium. Logistic progression was used for sta tistical 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%, eth ambutol 1.9%, streptomycin 4.7% and pyrazinamide 6.5%). Primary drug resist ance against isoniazid and pyrazinamide were associated with foreign people . The total acquired drug resistance was associated with people over 60 yea rs old and women. CONCLUSIONS: The low level of primary drug resistance enables antituberculo sis treatment of non-treated patients to start with the standardised three- drug regimes except in the case of foreign people from countries with a hig h level of drug resistance. Susceptibility tests are recommended on all M. tuberculosis strains isolated, together with controlled studies of drug res istance surveillance.