Genetic Determinants of Rifampicin Resistance of Mycobacterium tuberculosis not Included in the Russian Molecular Genetic Test Systems

The objective: to study the genetic determinants of rifampicin resistance of Mycobacterium tuberculosis by sequencing the RRDR rpoB gene. Subjects and Methods. The study included 651 M. tuberculosis isolates that were tested for drug suceptibility (DST) by genotypic methods (gDST) TB-TEST (BIOCHIP-IMB, Russia), and Amplitube-MDR-RV (NPK Sintol, Russia) and phenotypic methods (phDST): the absolute concentration method, BACTEC MGIT 960 system, and Sensititre Myco TB kit. Sanger RRDR sequencing of the rpoB gene was performed for 20 isolates with discrepancies in the results of phDST and gDST. Results. As a result of sequencing, two variants of mutations in the RRDR region of the rpoB gene were found, which were not detected by TB-TEST and Amblitub MDR-RV test systems, however were strongly associated with rifampicin resistance of Mycobacterium tuberculosis. The most common variant was the insertion of three nucleotides (TTC) encoding the amino acid phenylalanine at position 434 of the codon (1296-1300insTTC).