India has a high burden of drug-resistant tuberculosis (DR TB) and many cases go undetected by current drug susceptibility tests (DSTs). This study was conducted to identify rifampicin (RIF) and ...isoniazid (INH) resistance associated genetic mutations undetected by current clinical diagnostics amongst persons with DR TB in Chennai, India. Retrospectively stored 166 DR TB isolates during 2013-2016 were retrieved and cultured in Löwenstein-Jensen medium. Whole genome sequencing (WGS) and MGIT DST for RIF and INH were performed. Discordant genotypic and phenotypic sensitivity results were repeated for confirmation and the discrepant results considered final. Further, drug resistance-conferring mutations identified through WGS were analyzed for their presence as targets in current WHO-recommended molecular diagnostics. WGS detected additional mutations for rifampicin and isoniazid resistance than WHO-endorsed line probe assays. For RIF, WGS was able to identify an additional 10% (15/146) of
mutant isolates associated with borderline rifampicin resistance compared to MGIT DST. WGS could detect additional DR TB cases than commercially available and WHO-endorsed molecular DST tests. WGS results reiterate the importance of the recent WHO revised critical concentrations of current MGIT DST to detect low-level resistance to rifampicin. WGS may help inform effective treatment selection for persons at risk of, or diagnosed with, DR TB.
Abstract This study tested the mechanical efficacy of various irrigating needle tip designs on bacteria inoculated into instrumented root canals. Root canals of 30 extracted permanent canines were ...prepared to size 60 at working length (WL) using ProFile 0.04 taper rotary nickel-titanium files. Root canals were autoclaved and inoculated with a 20-μl suspension (1.4 × 107 cells) of genetically engineered Escherichia coli pYUB556 . Bioluminescence was measured before inoculation (baseline), after inoculation and after irrigation with 6 ml of saline using luminometer. Safety-ended needles with single (group 1) and double (group 2) side-port and hypodermic needles (group 3) were used upto 1 mm short of WL. The percentage of bacteria remaining after irrigation was 67.9 ± 9.5, 75.3 ± 12.9 and 77.7 ± 11.8 respectively (p < 0.05; Kruskal-Wallis) with no difference between group II and group III (p > 0.05; Mann-Whitney). Irrigation using safety needles with single side port was significantly effective.
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