Overcoming the Challenges of Pyrazinamide Susceptibility Testing in Clinical Mycobacterium tuberculosis Isolates
Simone Mok, Emma Roycroft, Peter R. Flanagan, Lorraine Montgomery, Emanuele Borroni, Thomas R. Rogers, Margaret Fitzgibbon
Abstract
genes. Of the 40 isolates, 16 (40%) were found to be susceptible using the reduced inoculum method (i.e., false resistance). No mutations were detected in two PZA-resistant isolates. False resistance was observed in isolates with MICs close to the critical concentration. In particular, East African Indian strains (lineage 1) appeared to have an elevated MIC that is close to the critical concentration. While this study illustrates the complexity and challenges associated with PZA susceptibility testing of M. tuberculosis, we conclude that a combination of genotypic and phenotypic drug susceptibility testing methods is required for accurate detection of PZA resistance.