Rapid detection of rifampin-resistant clinical isolates of Mycobacterium tuberculosis by reverse dot blot hybridization.

OBJECTIVE A PCR-reverse dot blot hybridization (RDBH) assay was developed for rapid detection of rpoB gene mutations in 'hot mutation region' of Mycobacterium tuberculosis (M. tuberculosis). METHODS 12 oligonucleotide probes based on the wild-type and mutant genotype rpoB sequences of M. tuberculosis were designed to screen the most frequent wild-type and mutant genotypes for diagnosing RIF resistance. 300 M. tuberculosis clinical isolates were detected by RDBH, conventional drug-susceptibility testing (DST) and DNA sequencing to evaluate the RDBH assay. RESULTS The sensitivity and specificity of the RDBH assay were 91.2% (165/181) and 98.3% (117/119), respectively, as compared to DST. When compared with DNA sequencing, the accuracy, positive predictive value (PPV) and negative predictive value (NPV) of the RDBH assay were 97.7% (293/300), 98.2% (164/167), and 97.0% (129/133), respectively. Furthermore, the results indicated that the most common mutations were in codons 531 (48.6%), 526 (25.4%), 516 (8.8%), and 511 (6.6%), and the combinative mutation rate was 15 (8.3%). One and two strains of insertion and deletion were found among all strains, respectively. CONCLUSION Our findings demonstrate that the RDBH assay is a rapid, simple and sensitive method for diagnosing RIF-resistant tuberculosis.