Performance of TaqMan array card to detect TB drug resistance on direct specimensReport as inadecuate

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Culture based phenotypic drug susceptibility testing DST for Mycobacterium tuberculosis TB is time consuming therefore rapid genotypic methods are increasingly being utilized. We previously developed and evaluated on TB isolates a rapid genotypic TaqMan array card TAC that detects mutations in several resistance-associated genes using dozens of primer pairs, probes, and high resolution melt analysis, with >96% accuracy versus Sanger sequencing. In this study we examined the performance of TAC on sputum, comparing results between 71 paired sputum and TB isolates of which 62 were MDR-TB. We also adapted the TAC to include wild-type probes and broadened coverage for rpoB and gyrA mutations. TAC was 89% successful at detecting wild-type or mutations within inhA, katG, rpoB, eis, gyrA, rplC, and pncA on smear positive sputa and 33% successful on smear negative sputa. The overall accuracy of these detections as compared to the TAC results of the paired isolate was 95% ± 7 average sensitivity 98% ± 3; specificity 92% ± 14. Accuracy of sputum TAC results versus phenotypic DST for isoniazid, rifampin, ofloxacin-moxifloxacin, and pyrazinamide was 85% ± 12. This was similar to that of the isolate TAC results accuracy 88% ± 13, thus inaccuracies primarily reflected intrinsic genotypic-phenotypic discordance. The TAC is a rapid, modular, comprehensive, and accurate TB DST for the major first and second line TB drugs and could be used for supplemental testing of GeneXpert resistant smear positive sputum.

Author: Sayera Banu , Suporn Pholwat , Suporn Foongladda , Rattapha Chinli, Duangjai Boonlert, Sara Sabrina Ferdous, S. M. Mazidur Rahman



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