Rapid Detection of rpoB Mutations in Rifampin Resistant M. tuberculosis from Sputum Samples by Denaturing Gradient Gel Electrophoresis

Objective: To establish a rapid detection method for identifying rpoB mutations associated with rifampin (RIF) resistance in sputum specimens. Methods: We detected rpoB mutations directly in 90 sputum specimens collected from suspected tuberculosis patients using PCR-based denaturing gradient gel electrophoresis (DGGE) and compared these results with those obtained by rpoB sequencing and conventional drug susceptibility testing. Results: The positive detection rate of Mycobacterium tuberculosis (M. tuberculosis) was 52.2% by Acid-Fast Bacilli staining and 72.2% by conventional mycobacterial culture. In contrast, the positive rate was significantly higher (93.3%) by PCR-based detection of the rpoB gene in the same specimens. Furthermore, 75% of the tested specimens presented abnormal patterns compared with the wild-type pattern (standard H37Rv strain) analysed by DGGE. A total of 12 different patterns, representing 12 different rpoB mutations, were observed in the 63 abnormal patterns. The match rate of rpoB mutations detected by DGGE reached 96.9% when compared to DNA sequencing. Conclusion: Our findings indicate that PCR-based DGGE is a rapid and reliable bio-technique for direct detection of rpoB mutations associated with RIF resistance in the sputum of suspected tuberculosis patients.