RESULTS: Based on conventional phenotypic DST 502 (74.5%) isolates were resistant to RIF. The rpoB gene sequencing showed 491 isolates possessed 517 mutation sites in the RRDR. The most frequent mutated site was codon 531 (185/517, 35.7%). Among the RIF-resistant isolates having the mutations at codon 533, most of the isolates (89%) showed minimal inhibitory concentration (MIC) lower than 16 ug/ml, suggesting that the mutation at codon 533 may not be associated with a high level of RIF resistance. Moreover, mutations at codon 533 (44/64, 68.8%) were frequently found in RIF-resistant and RBU-susceptible isolates. Sensitivity and specificity of the the rpoB gene sequencing and MTBDRplus were 93.4%, 91.4% and 91.4%, 95.1% respectively.