Detection of Drug-Resistant Mycobacerium tuberculosis Strains by Genotype Mtbdrplus Assay

Rapid identification of drug-resistance in Mycobacterium tuberculosis infections is crucial for early treatment and control of transmission. The MTBDRplus assay is potentially a practical and rapid alternative to the slower phenotypic drug susceptibility testing (DST) for detection of drug resistant tuberculosis (TB). The purpose of this study was to determine the diagnostic accuracy of the MTBDRplus assay. Sixty strains of Mycobacterium tuberculosis isolated from TB patients diagnosed in different parts of Poland in the two year period 2015-2016 were used. All strains were analyzed for drug susceptibility using both a conventional indirect proportion method and the MTBDRplus assay. The MTBDRplus assay identified 72% (43) of isolates as multidrug-resistant TB (MDR-TB), 7% (4) as INH-monoresistant and 5% (3) as RIF-monoresistant. The sensitivity and specificity of the MTBDRplus assay were 96% and 100% with respect to both RIFand INH-resistance, while sensitivity of the assay was lower (91%) for MDR-TB. In our study, codon 531 of rpoB gene and codon 315 of katG gene were found to have highest mutational frequency for RIF resistance (74% – 34 strains) and INH resistance (89% – 42 strains) respectively. The use of MTBDRplus assay as a supplement to the gold standard DST in obtaining a rapid preliminary DST result may contribute to early optimization of treatment.