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Year : 2009  |  Volume : 27  |  Issue : 3  |  Page : 226-230

Characterization of RPO B gene for detection of rifampicin drug resistance by SSCP and sequence analysis

National Institute of Communicable Diseases, Ministry of Health and FW, Government of India, 22-Shamnath Marg, Delhi-110 054, India

Correspondence Address:
S Gupta
National Institute of Communicable Diseases, Ministry of Health and FW, Government of India, 22-Shamnath Marg, Delhi-110 054
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/0255-0857.45364

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Purpose: Because of the emergence of multidrug-resistant tuberculosis in recent times, the rapid detection of resistance to the first-line anti-tuberculosis drug rifampicin was felt worldwide. Accordingly, this study was conducted to evaluate the diagnostic potential of polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP) for checking its utility as a rapid screening test for determination of rifampicin drug resistance. Materials and Methods: A total of 34 isolates of Mycobacterium tuberculosis ( M. tuberculosis ) (22 rifampicin resistant, 11 rifampicin sensitive and one control H37Rv) strains were analysed by PCR-SSCP and DNA sequencing within the 157-bp region of the rpo B gene (Ala 500 -Val 550 ). Results: Rifampicin resistance was detected successfully by PCR-SSCP in 20/22(90.90%) of rifampicin-resistant strains showing a total of nine different mutations in seven codon positions: codon 513 (CAA→CCA), 516 (GAC→GTC), 507 (GGC→GAC), 526 (CAC→GAC, TAC), 531 (TCG→TTG, TGG), 522 (TCG→TGG) and 533 (GTG→CCG). Two rifampicin-resistant strains showed an identical PCR-SSCP pattern with the wild type H37Rv; 77.27% rifampicin-resistant strains showed a single point mutation and 9.09% had no mutation. Three rifampicin-resistant strains showed characteristic double mutations at codon positions 526 and 531. Sensitivity and specificity were calculated as 90.90% and 100%. Conclusions: Rifampicin-resistant genotypes were mainly found in codon positions 516, 526 and 531. PCR-SSCP seems to be an efficacious method of predicting rifampicin resistance and substantially reduces the time required for susceptibility testing from 4 to 6 weeks to a few weeks.


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2004 - Indian Journal of Medical Microbiology
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