Since rifampicin resistance is a surrogate marker for multidrug-resistant Mycobacterium tuberculosis (MDRTB), the present study aimed to investigate rpoB mutations conferring rifampicin resistance in M. tuberculosis strains from Thailand, and to develop a rapid, inexpensive and simple PCR-based method for rapid detection of MDRTB. Overall, 267 M. tuberculosis isolates, including 143 MDRTB isolates, were investigated. Isolates of the Beijing strain predominated among the MDRTB isolates (79.1%), but accounted for only 45.5% of the susceptible isolates. Mutations in the rpoB gene were found most commonly at codons 531, 526 and 516 (58%, 25.2% and 9.1%, respectively). A multiplex allele-specific PCR was developed and tested with 216 clinical isolates. In comparison with the proportion method, the method showed 94.2% sensitivity and 100% specificity, and had a 100% positive predictive value and a 95% negative predictive value, which suggested that this method could be useful for screening for MDRTB, particularly in resource-limited countries.

No abstract

The aim of this study was the molecular characterization of primary drug-resistant Mycobacterium tuberculosis strains in Thailand. We examined a group of M. tuberculosis isolates from newly registered tuberculosis (TB) cases, collected at the largest university hospital, the Siriraj Hospital, in Thailand. Of 76 selected drug-resistant M. tuberculosis strains recovered from previously untreated pulmonary TB patients whose sputum samples were sent to this hospital, 29 (38%) were single-drug resistant, 26(34%) multidrug resistant and two (2.6%) extensively drug resistant. Fifty (66%) strains belonged to Beijing genotype. The study demonstrated a severe problem of drug resistance among recently detected TB patients, and two large clusters of genetically similar strains indicated ongoing transmission of drug-resistant TB.