Acquired drug resistance in Mycobacterium tuberculosis isolates from treated patients in the province of Bursa, Turkey

Abstract

Objective: To evaluate the distribution of acquired resistance in isolates of Mycobacterium tuberculosis from treated patients in two periods, 1984-89 and 1990-95, in the Bursa (Southern Marmara) region. Method: Susceptibility of 531 M. tuberculosis isolates to four commonly used drugs (isoniazid (INH), streptomycin (SM), ethambutol (EMB) and rifampin (RMP)) was determined by the absolute concentration method of Canetti et al. Results: In 203 strains isolated in the years 1984-89, the total acquired resistance was 32.5%, and it was 37.5% in 328 strains isolated in 1990-95 (p > 0.05). Resistance to INH, SM, RMP and EMB was found in 23.6%, 16.7%, 6.4% and 3.9%, respectively, in the first period (1984-89), and in 26.2%, 20.4%, 25.3% and 8.2%, respectively, in the second period (1990-95). The increase in RMP resistance was statistically significant (p < 0.001). The incidence of multidrug-resistant strains was 12.3% in the first period, and 24.4% in the second period, a significant increase (p < 0.001). Conclusions: We believe that progressive emergence of phenotypes resistant to INH + RMP in our region is caused by inadequate treatment for various reasons. In the present study, the fact that multidrug resistance occurred in nearly 25% of patients treated previously but still infective suggests that the approach to surveillance, patient therapy and follow-up programs should be fundamentally reconsidered in our region.