Frequency and implications of pyrazinamide resistance in managing previously treated tuberculosis patients

Int J Tuberc Lung Dis. 2006 Jul;10(7):802-7.


Objective: To determine the extent of pyrazinamide (PZA) resistance in isolates from previously treated patients from the Western Cape, South Africa.

Design: Drug-resistant isolates, isolates resistant to one or more drugs other than PZA (PZA resistance is not routinely determined) (n = 127), and drug-susceptible (n = 47) clinical isolates of Mycobacterium tuberculosis from previously treated patients from the Western Cape were phenotypically (BACTEC MGIT 960) and genotypically (pncA gene sequencing) analysed for PZA resistance.

Results: MGIT analysis found that 68 of the 127 drug-resistant isolates were PZA-resistant. Nearly all (63/68) PZA-resistant isolates had diverse nucleotide changes scattered throughout the pncA gene, and five PZA-resistant isolates had no pncA mutations. Of the 47 phenotypically susceptible isolates, 46 were susceptible to PZA, while one isolate was PZA-monoresistant (OR = 53.0, 95% CI = 7.1-396.5). A pncA polymorphism (Thr114Met) that did not confer PZA resistance was also identified. PZA resistance was strongly associated with multidrug-resistant tuberculosis (MDR-TB).

Conclusion: An alarmingly high proportion of South African drug-resistant M. tuberculosis isolates are PZA-resistant, indicating that PZA should not be relied upon in managing patients with MDR-TB in the Western Cape. A method for the rapid detection of PZA resistance would be beneficial in managing patients with suspected drug resistance.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Antitubercular Agents / pharmacology
  • Antitubercular Agents / therapeutic use*
  • Base Sequence
  • DNA Primers
  • Drug Resistance, Microbial* / genetics
  • Humans
  • Mutation
  • Mycobacterium tuberculosis / drug effects
  • Mycobacterium tuberculosis / genetics
  • Polymerase Chain Reaction
  • Pyrazinamide / pharmacology
  • Pyrazinamide / therapeutic use*
  • Tuberculosis / drug therapy*


  • Antitubercular Agents
  • DNA Primers
  • Pyrazinamide