Rapid detection of Mycobacterium tuberculosis and pyrazinamide susceptibility related to pncA mutations in sputum specimens through an integrated gene-to-protein function approach

J Clin Microbiol. 2014 Jan;52(1):260-7. doi: 10.1128/JCM.02285-13. Epub 2013 Nov 13.

Abstract

Testing the pyrazinamide (PZA) susceptibility of Mycobacterium tuberculosis isolates is challenging. In a previous paper, we described the development of a rapid colorimetric test for the PZA susceptibility of M. tuberculosis by a PCR-based in vitro-synthesized-pyrazinamidase (PZase) assay. Here, we present an integrated approach to detect M. tuberculosis and PZA susceptibility directly from sputum specimens. M. tuberculosis was detected first, using a novel long-fragment quantitative real-time PCR (LF-qPCR), which amplified a fragment containing the whole pncA gene. Then, the positive amplicons were sequenced to find mutations in the pncA gene. For new mutations not found in the Tuberculosis Drug Resistance Mutation Database (www.tbdreamdb.com), the in vitro PZase assay was used to test the PZA resistance. This approach could detect M. tuberculosis within 3 h with a detection limit of 7.8 copies/reaction and report the PZA susceptibility within 2 days. In an initial testing of 213 sputum specimens, the LF-qPCR found 53 positive samples with 92% sensitivity and 97% specificity compared to the culture test for M. tuberculosis detection. DNA sequencing of the LF-qPCR amplicons revealed that 49 samples were PZA susceptible and 1 was PZA resistant. In the remaining 3 samples, with new pncA mutations, the in vitro PZase assay found that 1 was PZA susceptible and 2 were PZA resistant. This integrated approach provides a rapid, efficient, and relatively low-cost solution for detecting M. tuberculosis and PZA susceptibility without culture.

Publication types

  • Evaluation Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Amidohydrolases / genetics
  • Amidohydrolases / metabolism
  • Antitubercular Agents / pharmacology*
  • Humans
  • Microbial Sensitivity Tests / methods
  • Molecular Diagnostic Techniques / methods*
  • Mutation, Missense
  • Mycobacterium tuberculosis / drug effects*
  • Mycobacterium tuberculosis / genetics
  • Mycobacterium tuberculosis / isolation & purification*
  • Pyrazinamide / pharmacology*
  • Real-Time Polymerase Chain Reaction / methods
  • Sensitivity and Specificity
  • Sequence Analysis, DNA
  • Sputum / microbiology*
  • Time Factors
  • Tuberculosis, Pulmonary / diagnosis*
  • Tuberculosis, Pulmonary / microbiology

Substances

  • Antitubercular Agents
  • Pyrazinamide
  • Amidohydrolases
  • PncA protein, Mycobacterium tuberculosis