Characterization of rpoB mutations in rifampin-resistant Mycobacterium tuberculosis isolates from the Middle East

The nature and frequency of mutations in the rpoB gene of rifampin-resistan t clinical Mycobacterium tuberculosis isolates vary considerably according to geographical locations. There is no information on the prevalence of spe cific mutations in clinical M. tuberculosis strains isolated from patients in Middle-Eastern countries. In this study, 13 rifampin-resistant and 6 sus ceptible clinical M. tuberculosis isolates were tested for identification a nd characterization of mutations in the rpoB gene by INNO-LiPA Rif. TB kit and DNA sequencing of the PCR amplified target DNA. The kit identified all six susceptible strains as rifampin-sensitive and the DNA sequence of the a mplified rpoB gene in the target region matched perfectly with the wild-typ e sequence. The kit identified 12 resistant isolates as rifampin-resistant with specific detection of mutations in 8 isolates while one of the rifampi n-resistant strain was identified as rifampin-susceptible. DNA sequencing c onfirmed these results and, in addition, led to the specific detection of m utations in 4 rifampin-resistant isolates in which specific base changes wi thin the target region could not be determined by the INNO-LiPA Rif. TB kit . The majority (8 of 13) of resistant isolates involved base changes at cod on 531 of the rpoB gene. Mutations at codon position 531 within the rpoB ge ne have also been reported in majority of rifampin-resistant strains from G reece and St. Petersburg, Russia but not from other geographical locations. (C) 2000 Elsevier Science Inc. AII rights reserved.