Comparison of PCR-line probe and PCR-SSCP methods for the detection of rifampicin resistant mycobacterium tuberculosis

Background: Rifampicin (RFP) is a key component of the antituberculous short-course chemotherapy and the RFP resistance is a marker of multi-drug resistant (MDR) tuberculosis. RpoB gene encodes the β-subunit of RNA polymerase of M. tuberculosis which is the target of RFP. And the mutations of rpoB gene have been found in about 96% of rifampicin resistant clinical isolates of M. tuberculosis. So in order to find a rapid and clinically useful diagnostic method in identifying the RFP resistance, we compared the PCR-line probe method with PCR-SSCP for the detection of the rpoB gene mutation in cultured M. tuberculosis. Methods: 45 clinical isolates were collected from patients who visited Sung Kyun Kwan University Hospital. The RFP susceptibility test was referred to the referral laboratory of the Korean Tuberculosis Institute. 33 were rifampicin resistant and 12 were rifampicin susceptible. The susceptibility results were compared with the results of the PCR-SSCP and PCR-line probe method. Results: We could find rpoB mutations in 27/33(81.8%) RFP-resistant strains by PCR-line probe method, and in 23/33(69.7%) by PCR-SSCP and there was no significant difference between two methods. There was no mutation in rifampicin susceptible strains by both methods. Conclusion: PCR-line probe method would be a rapid, sensitive and specific method for the detection of rifampicin resistant Mycobacterium tuberculosis.