Abstract
BackgroundAccording to World Health Organization (WHO), drug-resistant tuberculosis (DR-TB) is a major contributor to antimicrobial resistance globally and continues to be a public health threat. Annually, about half a million people fall ill with DR-TB globally. The gradual increase in resistance to fluoroquinolones (FQs) and second-line injectable drugs (SLIDs), poses a serious threat to effective TB control and adequate patient management. Therefore, WHO suggests the use of GenoType MTBDRsl v.2.0 assay for detection of multiple mutations associated with FQs and SLIDs. Hence, the study was conducted to determine the prevalence of resistance to FQs and SLIDs by comparing direct GenoType MTBDRsl v.2.0 assay with phenotypic drug susceptibility testing (DST).MethodsThe study was conducted on 1320 smear positive sputum samples from a total of 2536 RR-TB, confirmed by GeneXpert MTB/RIF. The smear positive specimens were decontaminated, and DNA extraction was performed. Furthermore, the extracted DNA was used for GenoType MTBDRsl v.2.0 assay. While 20% of the decontaminated specimens were inoculated in Mycobacterium growth indicator tube (MGIT) for drug susceptibility testing (DST).ResultsOut of 1320 smear positive sputum samples, 1178 were identified as Mycobacterium tuberculosis complex (MTBC) and remaining were negative by GenoType MTBDRsl v.2.0 assay. Of the 1178 MTBC positive, 26.6% were sensitive to both FQs and SLIDs, whereas 57.3% were only FQs resistant and 15.9% were resistant to both FQs and SLIDs. Further DST of 225 isolates by liquid culture showed that 17% were sensitive to both FQs and SLIDs, 61.3% were only FQs resistant and 21.3% were resistant to both. The specificity for FQs and SLIDs was 92.31% and 100% whereas sensitivity was 100% respectively by GenoType MTBDRsl v.2.0 assay in direct sputum samples.ConclusionsOur study clearly suggests that GenoType MTBDRsl v.2.0 assay is a reliable test for the rapid detection of resistance to second-line drugs after confirmation by GeneXpert MTB/RIF assay for RR-TB. Though, high rate FQ (ofloxacin) resistance was seen in our setting, moxifloxacin could be used as treatment option owing to very low resistance.
Highlights
According to World Health Organization (WHO), drug-resistant tuberculosis (DR-TB) is a major contributor to antimicrobial resistance globally and continues to be a public health threat
Drug susceptibility testing Of the 264 samples inoculated for culture, 225 isolates were found Mycobacterium tuberculosis complex (MTBC) positive in liquid culture, confirmed by immunochromatography-based MPT64 rapid antigen detection kit (SD BIOLINE TB Ag) with no growth on brain heart infusion (BHI) agar plate, whereas 39 were found contaminated
The specificity for FQs and second line injectable drugs (SLIDs) was 92.31% and 100% whereas sensitivity was 100% respectively by GenoType MTBDRsl v.2.0 assay in direct sputum samples when compared against phenotypic drug susceptibility testing (DST)
Summary
According to World Health Organization (WHO), drug-resistant tuberculosis (DR-TB) is a major contributor to antimicrobial resistance globally and continues to be a public health threat. The gradual increase in resistance to fluoroquinolones (FQs) and second-line injectable drugs (SLIDs), poses a serious threat to effective TB control and adequate patient management. Drug-resistant tuberculosis (DR-TB) has emerged as an enormous global challenge for TB control. It develops either because of an infection with a resistant strain or as a result of inadequate treatment. It is of grave concern to public health, with higher mortality rates than drug-susceptible TB [2]. These TB patients require treatment with second-line drugs that are costlier and have increased toxicity; and remain infectious longer than patients infected with drug-susceptible strains [3]. Drug-resistant TB (XDR-TB) is defined as MDR-TB plus resistance to fluoroquinolones (FQs) and one of the second line injectable drugs (SLIDs) utilized in MDR-TB treatment regimens [4]
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