Enabling Sciences Workgroup Q3-2015 Update
The mission of the ENS-WG is to focus on discovery and validation of the molecular basis for resistance and correlation of resistance to clinical outcome.
- Discover relevant drug resistant mutations for potential use in molecular assays.
- Correlate genetic resistance mutations with phenotypic resistance and clinical outcomes.
- Optimize phenotypic assays.
- Review existing genotypic, phenotypic or animal data suggestive of background resistance to new drugs or cross resistance within the same class of drugs.
- Standardize test methods in partnership with commercialization partners to qualify MIC assays for new and old drugs.
- Collaborate with other Workgroups in the development of a RDST data sharing platform.
- Collaborate with drug developers to clarify/interpret molecular drug resistance profiles.
- Understanding MOA and MOR to enable rapid DST development and evaluation of clinical isolates (both drug susceptible and drug resistant).
- The manuscript titled: Mycobacterium tuberculosis pncA polymorphisms that do not confer pyrazinamide resistance at a breakpoint concentration of 100 μg/ml in MGIT was published in the Journal of Clinical Microbiology in August, 2015.
- Another manuscript on 105 mutations that confer PZA resistance is in development and expected to be complete in Q4 2015.
- PncA next generation sequencing assay to distinguish wild type from mutant sequences is almost complete. An enzymatic assay was used for phenotypic correlation and high correlation was found for most. Examination of discordance results has required redesign of a few stop codons. The majority of codons confer resistance.
- Work on the Lights On/Lights Off assay platform to detect wild-type pncA is ongoing. The team ran blinded samples to test the platform, which identified 3 probes that require optimization. An abstract on this platform was accepted for the December 2015 Union Conference in South Africa.
- Phenotypic assay optimization is undergoing a multisite evaluation with 10 APHL labs to assess accuracy and reproducibility of the modified inoculation procedure to reduce false positive rates. Current results seem to indicate that diluted inoculation decreases the probability of false resistance.
- Otsuka and TB Alliance confirmed interest in the nitroimidazoles project to better understand resistance mechanisms and the level of background resistance in different geographical regions, lineages and populations. Work is ongoing with Barry Kreiswirth, with others applying for funding.
- A final design for a MIC Trek “clinical plate” is complete. This plate will test several thousand isolates from diverse collections and will hold 17 drugs which include 1st and 2nd line drugs (excluding PZA), as well as new and repurposed drugs. Trek received drugs from Janssen and began optimization studies to manufacture plates for preliminary evaluation. An MTA is being vetted between