Pyrazinamide (PZA) is a standard component of first-line treatment regimens for Mycobacterium tuberculosis (Mtb) and is included in treatment regimens for drug-resistant Mtb whenever possible. It is therefore imperative that susceptibility to PZA be reliably assessed prior to 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, NIPRO Genoscholar™⋅PZA-TB II, was developed for the detection of mutations within the pncA gene including the promoter region likely to lead to PZA resistance. The sensitivity and specificity of this assay was evaluated by two independent laboratories using a combined total of 249 strains with mutations in pncA and its promoter as well as 21 strains with wild-type pncA. Overall, the assay showed good sensitivity (93.2%, 95%CI 89.3, 95.8) and moderate specificity (91.2%, 95%CI 77.0, 97.0) for the identification of Mtb predicted to be resistant to PZA based upon 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.
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