Detection of Mycobacterium tuberculosis pncA Mutations by the Nipro Genoscholar PZA-TB II Assay Compared to Conventional Sequencing

Abstract

Pyrazinamide (PZA) is a standard component of first-line treatment regimens for Mycobacterium tuberculosis and is included in treatment regimens for drug-resistant M. tuberculosis whenever possible. Therefore, it is imperative that susceptibility to PZA be assessed reliably prior to the initiation of therapy. Currently available growth-based PZA susceptibility tests are time-consuming, and results can be inconsistent. Molecular tests have been developed for most first-line antituberculosis drugs; however, a commercial molecular test is not yet available for rapid detection of PZA resistance. Recently, a line probe assay, the Nipro Genoscholar PZA-TB II assay, was developed for the detection of mutations within the pncA gene, including the promoter region, that are likely to lead to PZA resistance. The sensitivity and specificity of this assay were evaluated by two independent laboratories, using a combined total of 249 strains with mutations in pncA or its promoter and 21 strains with wild-type pncA Overall, the assay showed good sensitivity (93.2% [95% confidence interval, 89.3 to 95.8%]) and moderate specificity (91.2% [95% confidence interval, 77.0 to 97.0%]) for the identification of M. tuberculosis strains predicted to be resistant to PZA on the basis of the presence of mutations (excluding known PZA-susceptible mutations) in the pncA coding region or promoter. The assay shows promise for the molecular prediction of PZA resistance.

Keywords: line probe assay; pncA; pyrazinamide; tuberculosis.