Evolution in the resistance of Mycobacterium tuberculosis to anti-tuberculosis drugs in Nicaragua.

ABSTRACT

SETTING: Nicaragua, a country where the DOTS strategy has been successfully implemented since 1984. OBJECTIVE: To estimate the prevalence and trends of Mycobacterium tuberculosis resistance to first-line anti-tuberculosis drugs. DESIGN: A prospective national survey carried out in 2004 according to the standardised model developed by the World Health Organisation and the International Union Against Tuberculosis and Lung Disease. RESULTS: A total of 423 M. tuberculosis strains were studied. Among the 320 strains evaluated for initial resistance, 13.1% displayed resistance to any drug, lower than the 1998 figure of 15.6%. Overall initial resistance to isoniazid (INH), rifampicin (RMP) and multidrug resistance (MDR) was respectively 6.6%, 0.9% and 0.6%. Initial resistance was higher in older age groups. Overall acquired resistance was 35.9% (n = 103); resistance to INH was 29.3% and to RMP 8.9%, while MDR was 7.9%. The acquired MDR rate was clearly higher in Category I failures (44.4%) than in relapses (3.8%) and retrieved defaulters (2.7%). All resistance rates found in this study were lower than those detected in 1998. CONCLUSION: This study shows low rates of resistance and MDR and a downward trend in all rates, undoubtedly related to the proper implementation of the National Tuberculosis Programme.