A high-throughput cidality screen for Mycobacterium tuberculosis

PLoS One. 2015 Feb 18;10(2):e0117577. doi: 10.1371/journal.pone.0117577. eCollection 2015.

Abstract

Exposure to Mycobacterium tuberculosis (Mtb) aerosols is a major threat to tuberculosis (TB) researchers, even in bio-safety level-3 (BSL-3) facilities. Automation and high-throughput screens (HTS) in BSL3 facilities are essential for minimizing manual aerosol-generating interventions and facilitating TB research. In the present study, we report the development and validation of a high-throughput, 24-well 'spot-assay' for selecting bactericidal compounds against Mtb. The bactericidal screen concept was first validated in the fast-growing surrogate Mycobacterium smegmatis (Msm) and subsequently confirmed in Mtb using the following reference anti-tubercular drugs: rifampicin, isoniazid, ofloxacin and ethambutol (RIOE, acting on different targets). The potential use of the spot-assay to select bactericidal compounds from a large library was confirmed by screening on Mtb, with parallel plating by the conventional gold standard method (correlation, r2 = 0.808). An automated spot-assay further enabled an MBC90 determination on resistant and sensitive Mtb clinical isolates. The implementation of the spot-assay in kinetic screens to enumerate residual Mtb after either genetic silencing (anti-sense RNA, AS-RNA) or chemical inhibition corroborated its ability to detect cidality. This relatively simple, economical and quantitative HTS considerably minimized the bio-hazard risk and enabled the selection of novel vulnerable Mtb targets and mycobactericidal compounds. Thus, spot-assays have great potential to impact the TB drug discovery process.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Antitubercular Agents / pharmacology*
  • Drug Evaluation, Preclinical / methods*
  • Drug Evaluation, Preclinical / standards
  • High-Throughput Screening Assays / methods*
  • High-Throughput Screening Assays / standards
  • Microbial Sensitivity Tests
  • Mycobacterium tuberculosis / drug effects*
  • Reference Standards
  • Safety

Substances

  • Antitubercular Agents

Grants and funding

This study was conducted exclusively at AstraZeneca with no external funding. The funder had no role in the design of the study, data collection and analysis, decision to publish, or preparation of the manuscript.