opc-67683 and resazurin

The emergence of drug-resistant tuberculosis (TB) poses a serious challenge to existing anti-TB therapies. Hence, there is a direct need for identification of new drugs and effective combination regimens.. In this study, minimum inhibitory concentrations (MICs) of the anti-TB drugs bedaquiline (BDQ), delamanid (DEL) and moxifloxacin (MFX) were evaluated using a resazurin microtiter assay (REMA) against five drug-resistant clinicalMycobacterium tuberculosis (MTB) isolates as well as the drug-susceptible reference strain H37Rv. In addition, their fractional inhibitory concentration indices (FICIs) were evaluated using a REMA-based calorimetric chequerboard assay to assess their interaction profiles against the MTB isolates.. The FICI indicated that BDQ acted synergistically with DEL against isoniazid (INH)-monoresistant, rifampicin (RIF)-monoresistant and extensively drug-resistant (XDR) clinical MTB isolates. In addition, the combination of DEL acted synergistically with MFX against INH-monoresistant, RIF-monoresistant and XDR clinical MTB isolates. Moreover, the combination of BDQ and MFX showed a synergistic effect against RIF-monoresistant and pre-XDR clinical MTB isolates. DEL at 0.125×MIC (i.e. 0.015μg/mL) used in combination with BDQ at 0.25×MIC (i.e. 0.015μg/mL) had a stronger bactericidal effect against the XDR-TB clinical isolate than DEL alone at 1×MIC (i.e. 0.125μg/mL).. Synergistic and additive effects between these two-drug combinations offer an attractive chemotherapeutic regimen against drug-resistant clinical MTB isolates.

Topics: Antitubercular Agents; Diarylquinolines; Drug Resistance, Multiple, Bacterial; Drug Synergism; Extensively Drug-Resistant Tuberculosis; Humans; Microbial Sensitivity Tests; Moxifloxacin; Mycobacterium tuberculosis; Nitroimidazoles; Oxazines; Oxazoles; Tuberculosis, Multidrug-Resistant; Xanthenes

The objective of this study was to develop standardized protocols for rapid delamanid drug susceptibility testing (DST) using the colorimetric resazurin microtitre assay (REMA) and semi-automated BACTEC™ MGIT™ 960 system (MGIT) by establishing breakpoints that accurately discriminate between susceptibility and resistance of Mycobacterium tuberculosis to delamanid.. MICs of delamanid were determined by the MGIT, the REMA and the solid agar method for 19 pre-characterized strains. The MIC distribution of delamanid was then established for a panel of clinical strains never exposed to the drug and characterized by different geographical origins and susceptibility patterns. WGS was used to investigate genetic polymorphisms in five genes (ddn, fgd1, fbiA, fbiB and fbiC) involved in intracellular delamanid activation.. We demonstrated that the REMA and MGIT can both be used for the rapid and accurate determination of delamanid MIC, showing excellent concordance with the solid agar reference method, as well as high reproducibility and repeatability. We propose the tentative breakpoint of 0.125 mg/L for the REMA and MGIT, allowing reliable discrimination between M. tuberculosis susceptible and resistant to delamanid. Stop codon mutations in ddn (Trp-88 → STOP) and fbiA (Lys-250 → STOP) have only been observed in strains resistant to delamanid.. We established protocols for DST of delamanid in the MGIT and REMA, confirming their feasibility in routine TB diagnostics, utilizing the same discriminative concentration for both methods. Moreover, taking advantage of WGS analysis, we identified polymorphisms potentially associated with resistance in two genes involved in delamanid activation.

Topics: Antitubercular Agents; Automation, Laboratory; Colorimetry; Genes, Bacterial; Indicators and Reagents; Microbial Sensitivity Tests; Mycobacterium tuberculosis; Nitroimidazoles; Oxazines; Oxazoles; Polymorphism, Genetic; Sequence Analysis, DNA; Xanthenes