MODS-Wayne, a colorimetric adaptation of the Microscopic-Observation Drug Susceptibility (MODS) assay for detection of mycobacterium tuberculosis pyrazinamide resistance from sputum samples

Roberto Alcántara, Patricia Fuentes, Ricardo Antiparra, Marco Santos, Robert H. Gilman, Daniela E. Kirwan, Mirko Zimic, Patricia Sheen

Research output: Contribution to journalArticlepeer-review

Abstract

Although pyrazinamide (PZA) is a key component of first- and second-line tuberculosis treatment regimens, there is no gold standard to determine PZA resistance. Approximately 50% of multidrug-resistant tuberculosis (MDR-TB) and over 90% of extensively drug-resistant tuberculosis (XDR-TB) strains are also PZA resistant. pncA sequencing is the endorsed test to evaluate PZA susceptibility. However, molecular methods have limitations for their wide application. In this study, we standardized and evaluated a new method, MODS-Wayne, to determine PZA resistance. MODS-Wayne is based on the detection of pyrazinoic acid, the hydrolysis product of PZA, directly in the supernatant of sputum cultures by detecting a color change following the addition of 10% ferrous ammonium sulfate. Using a PZA concentration of 800 μg/ml, sensitivity and specificity were evaluated at three different periods of incubation (reading 1, reading 2, and reading 3) using a composite reference standard (MGIT-PZA, pncA sequencing, and the classic Wayne test). MODS-Wayne was able to detect PZA resistance, with a sensitivity and specificity of 92.7% and 99.3%, respectively, at reading 3. MODS-Wayne had an agreement of 93.8% and a kappa index of 0.79 compared to the classic Wayne test, an agreement of 95.3% and kappa index of 0.86 compared to MGIT-PZA, and an agreement of 96.9% and kappa index of 0.90 compared to pncA sequencing. In conclusion, MODS-Wayne is a simple, fast, accurate, and inexpensive approach to detect PZA resistance, making this an attractive assay especially for low-resource countries, where TB is a major public health problem.

Original languageEnglish (US)
Article numbere01162
JournalJournal of clinical microbiology
Volume57
Issue number2
DOIs
StatePublished - Feb 2019

Keywords

  • MODS
  • Pyrazinamide
  • Pyrazinoic acid
  • Sputum
  • Tuberculosis

ASJC Scopus subject areas

  • Microbiology (medical)

Fingerprint

Dive into the research topics of 'MODS-Wayne, a colorimetric adaptation of the Microscopic-Observation Drug Susceptibility (MODS) assay for detection of mycobacterium tuberculosis pyrazinamide resistance from sputum samples'. Together they form a unique fingerprint.

Cite this