Susceptibility of Mycobacterium tuberculosis to pyrazinamide and its relationship to pyrazinamidase activity

Pyrazinamidase activity has been associated with pyrazinamide-susceptible Mycobacterium tuberculosis strains. The detection of pyrazinamidase activity by the Wayne method was found to be of limited value when compared with the results of standard pyrazinamide susceptibility tests, especially when a high level of pyrazinamide resistance was found. When resistance to pyrazinamide reached a level of 150 to 200 micrograms/ml, there was too much variability in Wayne test results to accurately define pyrazinamide susceptibility.