Mutation in pncA is a major mechanism of pyrazinamide resistance in Mycobacterium tuberculosis

Tuber Lung Dis. 1997;78(2):117-22. doi: 10.1016/s0962-8479(98)80004-x.


Objective: To characterize the correlation of the mutations in the pncA gene encoding pyrazinamidase (PZase) of Mycobacterium tuberculosis to a loss of PZase activity and development of pyrazinamide (PZA) resistance.

Design: The association of PZase activity, minimum inhibitory concentrations (MICs), and mutations in the pncA gene of M. tuberculosis isolated in mostly Asian countries was investigated.

Results: One hundred thirty-five out of 168 isolates were PZase positive, and 33 were negative. The MICs of PZA at pH 6.0 were over 400 micrograms/ml for all 33 PZase-negative isolates, while those of PZase-positive isolates were equal to or less than 200 micrograms/ml. Among 33 PZase-negative isolates sequenced, 32 (97%) had mutations within the pncA gene. A mutation was seen in various regions throughout the pncA gene. It was surprising that all three strains of in vitro selected PZA resistant mutants were PZase-positive and showed no change in the pncA gene. These results indicate that additional mechanisms may be involved in PZA resistance. No mutations were observed in all of 135 PZase-positive M. tuberculosis isolates tested, indicating that mutations in the pncA gene could be involved in the loss of PZase activity.

Conclusions: Sequencing analysis of the pncA gene should provide rapid diagnosis of PZA resistant clinical isolates of M. tuberculosis.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amidohydrolases / genetics*
  • Drug Resistance, Microbial / genetics*
  • Microbial Sensitivity Tests
  • Mutation*
  • Mycobacterium tuberculosis / enzymology
  • Mycobacterium tuberculosis / genetics*
  • Polymerase Chain Reaction
  • Pyrazinamide


  • Pyrazinamide
  • Amidohydrolases
  • pyrazinamide deamidase