Characterization by single strand conformation polymorphism of mutations in the rpoB gene of rifampin-resistant Mycobacterium tuberculosis in strains from Vancouver, Mexico City and New Delhi.

OBJECTIVE: The study was conducted to evaluate usefulness of single strand conformation polymorphism (SSCP) over DNA sequencing in the diagnosis of rifampicin (Rif)-resistant tuberculosis. METHODS: Forty seven isolates of Mycobacterium tuberculosis (MTB) Rif-resistant and 25 Rif-sensitive were obtained from Vancouver, Mexico city and New Delhi and were analyzed by polymerase chain reaction (PCR) amplification of rpoB gene and the mutations were identified by DNA sequencing and SSCP. RESULTS: The mutations observed by DNA sequencing in 47 RIF-resistant isolates showed that the most common mutation among Vancouver isolates was in codon 526, Hist-->Arg and in Mexico isolates was in codon 531, Ser-Leu and New Delhi isolates was in codon 516, Asp-->Val. Using fluorescence based PCR-SSCP, it was possible to distinguish Rif-resistant isolates from Rif-sensitive isolates. CONCLUSION: DNA sequencing is a highly accurate method for the detection of mutations associated with drug resistance in tuberculosis but is more expensive and requires special equipment and personnel. SSCP is a simple, accurate method and suitable for analysis of large number of samples and the results are available in less than 72 hours.