[Determination of rifampin resistance in Mycobacterium tuberculosis isolates by the RNA/RNA mismatch method]

Rifampin is one of the most potent antituberculosis drugs and therefore, rifampin resistance leads to high clinical relapse rates. Detection of rifampin resistance could be an indication of multidrug resistance. In the recent years several molecular methods have been developed to evaluate the mutations in rpoB gene for the detection of rifampin resistance. The aim of the present study was to evaluate the performance of the RNA/RNA Mismatch Assay for detection of the mutations in the rpoB gene in 20 M. tuberculosis isolates which were determined as resistant to rifampin by agar proportion method. While RNA/RNA Mismatch Assay detected the mutations in the rpoB region in 16 of 20 (80%) M. tuberculosis isolates, the remaining four isolates yielded no band pattern indicating resistance. However, there may be situations where interpretation of the results is difficult in RNA/RNA Mismatch Assay which is already cheaper than DNA sequencing and other molecular methods. In conclusion, if the RNA/RNA Mismatch Assay can be optimized, it can be used for the rapid detection of rifampin resistance.