Sequencing of the entire rpob gene and characterization of mutations in isolates of Mycobacterium tuberculosis circulating in an endemic tuberculosis setting

rpoB gene mutations in rifampin-resistant Mycobacterium tuberculosis isolates from rural areas of Zhejiang, China

Objective

The aim was to analyze genetic mutations in the rpoB gene of rifampin-resistant Mycobacterium tuberculosis isolates (RIF^R-MTB) from Zhejiang, China.

Methods

We prospectively analyzed RIF^R-associated mutations in 13 rural areas of Zhejiang. Isolates were subjected to species identification, phenotype drug susceptibility testing (DST), DNA extraction, and rpoB gene sequencing.

Results

A total of 103 RIF^R isolates were identified by DST (22 RIF^R only, 14 poly-drug resistant, 49 multidrug resistant, 13 pre-extensively drug resistant [pre-XDR], and 5 extensively drug resistant [XDR]) from 2152 culture-positive sputum specimens. Gene sequencing of rpoB showed that the most frequent mutation was S450L (37.86%, 39/103); mutations P280L, E521K, and D595Y were outside the rifampicin resistance-determining region (RRDR) but may be associated with RIF^R. Mutations associated with poly-drug resistant, pre-XDR, and XDR TB were mainly located at codon 445 or 450 in the RRDR.

Conclusions

The frequency of rpoB RRDR mutation in Zhejiang is high. Further studies are needed to clarify the relationships between RIF^R and the TTC insertion at codon 433 in the RRDR and the P280L and D595Y mutations outside the RRDR.