Comparison of DNA sequencing, PCR-SSCP and PhaB assays with indirect sensitivity testing for detection of rifampicin resistance in Mycobacterium tuberculosis.

SETTING Tuberculosis Research Centre, Chennai, India. OBJECTIVE To rapidly identify multidrug-resistant Mycobacterium tuberculosis using phenotypic and genotypic methods. DESIGN Two genotypic assays, DNA sequencing and polymerase chain reaction single strand conformation polymorphism (PCR-SSCP), and one phenotypic assay, phage amplified biological assay (PhaB) were standardised in-house and performed on coded 101 rifampicin-resistant and 100 rifampicin-sensitive M. tuberculosis clinical isolates for the identification of rifampicin resistance. RESULTS AND CONCLUSION The results obtained using the three assays were compared with those from the conventional indirect sensitivity test. The sensitivities and specificities of DNA sequencing, PCR-SSCP and PhaB were 97% and 100%, 76% and 100%, and 97% and 84%, respectively. DNA sequencing was found to be more sensitive and specific than the other tests.