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The emergence of drug-resistant M. tuberculosis is a globalconcern. Rapid, simple drug susceptibility tests applicable in developing countries would allow earlier treatment of patients with MDR infections.
The aim of our study was to evaluate two techniques for the rapid identification of MDR-TB. REMA assay as a phenotypic technique and the HRM-curve assay as a genotypic technique.
Thirty M. tuberculosis clinical isolates of known resistance phenotypes were used. HRM curve was generated for each isolate to scan for mutations in the rpoB, and katG genes to detect RMP and INH resistance. The REMA colorimetric assay was also evaluated using the same isolates. The results of both techniques were compared to the gold standard proportional method.
The sensitivity, specificity, positive predictive Value (PPV), negative predictive value (NPV) and accuracy of REMA assay for RMP and INH susceptibility testing were 100%, while HRM curve assay results for RMP susceptibility testing were 92.3%, 100%, 100%, 94.4% and 96.7%, respectively, and for INH were 85%, 100%, 100%, 76.9% and 90%, respectively.
• The use of the REMA and HRM curve assay for rapid detection of RMP and INH resistance shows a high level of agreement with the PM.
• These new alternative methods seem to have the potential to provide rapid detection of resistance to RMP and INH, and reduce the time to report first results compared to classical conventional methods.
• REMA is simple and easy to perform; it does not need special instruments for reading the results.
• REMA is cheap and the method does not need any expensive equipment.
• REMA shows 100% sensitivity, specificity and accuracy for both RMP and INH when compared to the gold standard PM, and so it can be used as an alternative method for drug susceptibility testing for anti-tuberculous drugs especially in the low resource countries.
• HRM curve assay is also simple, but has lower sensitivity, specificity and accuracy when compared to both PM and the REMA assay.
• HRM curve assay is more suitable as screening technique before confirmation by more accurate techniques like DNA sequencing.
• Although this assay is cheaper than other genotypic techniques, but still expensive compared to phenotypic techniques, which makes this technique difficult to be applied routinely in low-resource countries.