LAUSR

Drug-resistant tuberculosis (TB) is a great challenge in TB control. The frequency and mutation characteristics can imply the efficiency of molecular tests for the rapid detection of TB drug resistance. This study examined the existence of mutations in katG and inhA for isoniazid (INH) resistance, and rpoB for rifampicin (RIF) resistance. A total of 178 drug-resistant Mycobacterium tuberculosis (MTB) isolates were analyzed. Mutations in katG encoding and inhA regulatory regions were detected in 136/168 (81.0%) and 29/168 (17.3%), respectively, with the most prominent mutation of Ser315Thr substitution in katG in 126/168 (75.0%), and -15 C > T substitution in the regulatory region of the inhA (26/168; 15.5%). Two distinct katG mutations (Tyr337Cys, 1003InsG) were identified. Of 125 RIF-resistant isolates, 118 (94.4%) carried mutations affecting the 81-bp RIF resistance-determining region (RRDR) with the most commonly affected codons 450, 445, and 435 identified in 74 (59.2%), 26 (20.8%) and 12 (9.6%) isolates, respectively. The genetic mutations were highly associated with phenotypic INH and RIF resistance, and the majority shared similarities with those in previous studies in Thailand and other Asian countries. The data is useful for guiding the use and the improvement of molecular tests for TB-drug resistance.