Diagnostic utility of GenoType MTBDRsl assay for the detection of moxifloxacin-resistant mycobacterium tuberculosis, as compared to phenotypic method and whole-genome sequencing.

Background: Recently, moxifloxacin (MFX)-resistant results of Mycobacterium tuberculosis (Mtb) obtained by GenoType MTBDRsl (second-line line probe assay [SL-LPA]) have been stratified to determine their resistance level; however, its accuracy has not been well studied. Therefore, the study aimed to evaluate the diagnostic accuracy of SL-LPA, with phenotypic drug susceptibility testing (pDST) and whole-genome sequencing (WGS) for the detection of MFX-resistant Mtb and their resistance level. Methods: A total of 111 sputum samples were subjected to SL-LPA according to the diagnostic algorithm of the National Tuberculosis Elimination Program. Results were compared with pDST of MFX (at critical concentration [CC, 0.25 µg/ml] and clinical breakpoint [CB, 1.0 µg/ml] using BACTEC mycobacterial growth indicator tube-960), and WGS. Results: At CC, SL-LPA and pDST yielded concordant results of MFX for 104 of 111 (94%). However, at CB, 23 of 30 (77%) isolates carrying gyrA mutation known to confer low-level resistance to MFX were scored as susceptible by pDST. Among 46 Mtb isolates carrying gyrA mutations known to confer high-level resistance to MFX, 36 (78%) isolates yielded concordant results, while 10 (22%) isolates were scored as susceptible at CB by pDST. WGS identified gyrA mutations in all isolates suggested by SL-LPA. Conclusion: It is concluded that the stratification of MFX-resistant results by SL-LPA/genotypic method is not very well correlated with pDST (at CB), and hence, pDST may not be completely replaced by SL-LPA. gyrA D94G and gyrAA90V are the most prevalent mutations in MFX-resistant Mtb.

Detection of multidrug and extensively drug-resistance and mutation pattern in geriatric patients from North Indian referral institute.

INTRODUCTION: Geriatric population are predisposed to reactivation to tuberculosis (TB) and multi-drug resistance (MDR) due to deteriorated immune system. Limited data is available in this population hence present study is undertaken to study drug resistance and associated mutations among geriatric presumptive DR-TB patients by genotypic methods METHODS: From October 2011 to December 2018, demographic characteristics of enrolled patients was collected. Smear-positive processed sputum samples were subjected directly while cultures positive for Mycobacterium Tuberculosis (MTB) from smear-negative pulmonary and all extra-pulmonary samples were subjected to LPA. The LPA used were Genotype MTBDR plus (1st line LPA) for detection of susceptibility to rifampicin (RIF) and isoniazid (INH) and Genotype MTBDR sl (2nd line LPA), for susceptibility to fluoroquinolones (FQ) and aminoglycosides (AG). RESULTS: Total of 2041 samples were received from presumptive MDR-TB patients above 60 years of age during study period, of which 1406; 68.9% were within 60-70 year followed by 495; 24.3% within 71-80 year and 140; 6.9% more than 80 years. Total of 1055 MTB were detected, of which those diagnosed as RIF resistant were 117/1055; 11.2% including 89/1055; 8.5% MDR-TB and resistance to INH was in 84/1055; 8%. Total 67, 2nd line LPA gave valid results, of which 19/67 (28.4%) isolates were resistant to only FQ, and one isolate was resistant to AG. CONCLUSION: Study finding highlights need for dedicated efforts for diagnosis, and treatment of geriatric tuberculosis. Suitable intervention at programmatic country level at country will help in strengthening tuberculosis control strategies in this population.

Frequency of multi-drug resistance and mutations in Mycobacterium tuberculosis isolates from Punjab state of India.

Data regarding prevalence of multi-drug resistant tuberculosis (MDR-TB) and associated common mutations is scarce from Punjab region. The study was designed to determine rate of MDR-TB among presumptive MDR-TB from Punjab and mutation patterns using GenoType MTBDRplus assay. Total of 812 consecutive sputum samples were received from January 2012 to July 2013, from 14 districts of Punjab at the National Reference Laboratory at New Delhi for diagnosis of MDR-TB as hand holding activity. Presumptive MDR-TB patients were identified on basis of criterion B defined by the programme. Smear positive and negatives patients were found to be 636/798 (79.7%) and 162/ 798 (20.3%) respectively. Total of 606 GenoType MTBDRplus tests were conducted and mutations in rpoB, kat G and inhA genes analyzed. Total of 94/606 (15.5%), 43/606 (7.1%) and 40/606 (6.6%) were found to be RIF and INH resistant, mono-RIF resistant and 40/606 (6.6%) mono-INH resistant respectively. Commonest known mutation for RIF in rpoB gene and INH in kat G gene was S531L (80/ 137; 58.4%) and S315T1 (119/134; 88.8%) respectively. Mutations in inhA were found in 21/134 (15.7%) strains. Average turn-around time (TAT) for dispatch of result toPunjab was 4.6days. Prevalence of RIF resistance in Punjab was found to be 22.6%. Common mutations for RIF and INH were similar to that in other regions of country. GenoType MTBDRplus was found to be useful assay for rapid detection of MDR-TB, responsible for determining better management of MDR-TB patients under the programme.