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 ORIGINAL ARTICLE
Year : 2014  |  Volume : 32  |  Issue : 4  |  Page : 398-403

Rapid screening of rpoB and katG mutations in Mycobacterium tuberculosis isolates by high-resolution melting curve analysis


1 Department of Microbiology, School of Biology, College of Science;School of Medicine, University of Tehran, Tehran, Iran
2 Applied Microbiology Research Center; Bagiyatallah University of Medical Sciences, Tehran, Iran
3 Department of Mycobacteriology, Massoud Laboratory, Tehran, Iran
4 Pediatric Infectious Disease Research Center, Tehran University of Medical Sciences, Tehran, Iran
5 Department of Microbiology, School of Biology, College of Science, University of Tehran, Tehran, Iran
6 School of Medicine, Tehran University of Medical Sciences, Tehran, Iran

Correspondence Address:
M M Feizabadi
School of Medicine, Tehran University of Medical Sciences, Tehran
Iran
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0255-0857.142245

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Background: Early detection of multidrug-resistant tuberculosis (MDR-TB) is essential to prevent its transmission in the community and initiate effective anti-TB treatment regimen. Materials and Methods: High-resolution melting curve (HRM) analysis was evaluated for rapid detection of resistance conferring mutations in rpoB and katG genes. We screened 95 Mycobacterium tuberculosis clinical isolates including 20 rifampin resistant (RIF-R), 21 isoniazid resistant (INH-R) and 54 fully susceptible (S) isolates determined by proportion method of drug susceptibility testing. Nineteen M. tuberculosis isolates with known drug susceptibility genotypes were used as references for the assay validation. The nucleotide sequences of the target regions rpoB and katG genes were determined to investigate the frequency and type of mutations and to confirm HRM results. Results: HRM analysis of a 129-bp fragment of rpoB allowed correct identification of 19 of the 20 phenotypically RIF-R and all RIF-S isolates. All INH-S isolates generated wild-type HRM curves and 18 out of 21 INH-R isolates harboured any mutation in 109-bp fragment of katG exhibited mutant type HRM curves. However, 1 RIF-R and 3 INH-R isolates were falsely identified as susceptible which were confirmed for having no mutation in their target regions by sequencing. The main mutations involved in RIF and INH resistance were found at codons rpoB531 (60% of RIF-R isolates) and katG315 (85.7% of INH-R isolates), respectively. Conclusion: HRM was found to be a reliable, rapid and low cost method to characterise drug susceptibility of clinical TB isolates in resource-limited settings.






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