ABSTRACT
Advancements in molecular technology increased our understanding of genetic mechanism of drug resistance. Nowadays, the chance of rapid detection of resistant Mycobacterium tuberculosis [M. tuberculosis] strains is increased. In the present study, we aimed to investigate the sensitivity and specificity of PCR-SSCP for detecting susceptible and resistant strains of M. tuberculosis compared with DNA sequencing. To calculate the sensitivity and specificity of PCR-SSCP assay to detect drug resistance in M. tuberculosis, respiratory samples were collected from suspected patients referred to Mycobacteriology Research Center [Masieh Daneshvary Hosptial] since 2002. Susceptibility testing against first line drugs was performed on 74 culturepositive specimens. Consequently, PCR-SSCP and DNA sequencing were performed on katG, inhA, ahpC and rpoB genes. Drug-susceptibility testing by the proportional method in selected samples revealed 16 MDR [21.6%], 23 mono-drug resistant [31%] and 35 susceptible strains [47.3%]. In comparison with DNA sequencing as a gold standard for molecular methods, the sensitivity of PCR-SSCP assay for detecting of mutation in 315 codon of katG gene was 94.74% [CI=73.97%-99.87%] with 100% [CI=93.51%-100%] specificity. In contrast, the sensitivity and specificity of this assay in detecting of rpoB gene were 70.8% [CI=48.91%-87.38%] and 88% [CI=75.69%-95.47%], respectively. PCR-SSCP in combination with DNA sequencing can be used as screening method to detect MDR-TB and mono-drug resistant cases