Comparison and development of pyrazinamide susceptibility testing methods for tuberculosis in Thailand

•We developed 2 new pyrazinamide susceptibility testing method for tuberculosis.•MTT and phage assays provided reasonable accuracy against the PZA MGIT method.•MTT assay requires no specialized instruments and turnaround time is similar to MGIT.•Phage assay requires real-time PCR system but turnaround time is shorter than MGIT.•MTT and phage could be used depending on a laboratory’s capabilities and resources.

Pyrazinamide (PZA) plays a critical role in shortening tuberculosis treatment duration and in treating multi-drug resistant tuberculosis (MDR-TB). The standard phenotypic MGIT PZA susceptibility testing method is imperfect because it is slow and has potential for false resistance. In this study, we evaluated 2 different phenotypic-based methods, quantitative real-time PCR (qPCR) phage assay, and MTT assay, as well as genotypic sequencing. The assay was evaluated on 71 clinical Mycobacterium tuberculosis isolates (37 MGIT PZA susceptible and 34 MGIT PZA resistant) and compared to the MGIT result. Of these methods, the qPCR phage assay yielded an accuracy of 89% versus standard MGIT while MTT yielded 83%. The genotypic sequencing method yielded 90% accuracy. We conclude that any of these faster PZA susceptibility methods perform reasonably well against a MGIT PZA susceptibility standard.