[Susceptibility of M. tuberculosis to antituberculosis drugs as determined by two methods, in Sucre state, Venezuela]

The objective of this study was to evaluate the resistance to isoniazid (INH), rifampicin (RIF), streptomycin (STR) and ethambutol (EMB), with the Canetti's proportions method (PM) and the nitrate reductase assay (NRA) of 59 clinical strains of Mycobacterium tuberculosis, isolated in the period of august 2005 to december 2006, in Sucre state, Venezuela. Primary and acquired drug resistance was 6.3% and 14.3%, respectively. Only one strain was found to be multidrug resistant (MDR). The overall agreement between the NRA and PM was 100% for INH, RIF and EMB, and 96% for STR. The time to obtain results was 10 to 14 days for the NRA, compared to 42 days for the PM. The NRA was easy to perform and therefore represents a useful tool for rapid and accurate determination of drug-resistant M. tuberculosis. The sequence of the rpoB gene of the RIF resistant strain demonstrated a never described mutation (change in the codon 456; TCG > CAG) in the hypervariable region of 81 base pairs where most of the mutations of the RIF resistant strains have been reported. Comparison of our results with those of the last resistance prevalence study carried out in the years 1998-1999, shows a decrease in the studied area.