[Study on the characteristics of mutation on Mycobacterium tuberculosis rifampicin-resistance gene]

To elucidate the characters of rpoB mutation in rifampin-resistant clinical isolates of Mycobacterium tuberculosis.

286 bp DNA fragment of rpoB gene including 81 bp code region (rifampin resistance deteremination region, RRDR) was analyzed by PCR-single-strand conformation polymorphism(SSCP). The 286 bp DNA fragment of each strain which had been proved to have mutation by PCR-SSCP was then sequenced. 110 strains of M. tuberculosis, including 73 rifampin-resistant strains, 11 rifampin-susceptible drug-resistant strains and 26 drug-susceptible strains were studied.

47 rifampin-resistant strains were detected to have mutations by PCR-SSCP method. 76.6% rifampin-resistant strains showed that rpoB gene was carrying single point mutation analyzed by direct sequencing technique, which mainly located at 531-Ser (61.1%) and 526-His (25.0%). The combined mutation rate was 23.4%. In addition, 2 rifampin-susceptible drug-resistant strains and 1 drug-susceptible strain were mutated, detected by PCR-SSCP method. Sequencing results showed that the mutations located at 511-Leu, 526-His and 535-Pro.

Mutations in the 81 bp RRDR of rpoB were the main reasons of M. tuberculosis resistant to rifampin. 531-Ser and 526-His were the most common positions of mutations.