Phenotypic and genotypic characterization of pyrazinamide resistance among multidrug-resistant Mycobacterium tuberculosis clinical isolates in Hangzhou, China

Objectives: Pyrazinamide (PZA) is a crucial first-line tuberculosis (TB) drug recommended for both drug-susceptible and multidrug-resistant Mycobacterium tuberculosis. This study aimed to evaluate the performance of the sequencing method of pncA, rpsA and panD mutations in detecting PZA resistance in multidrug-resistant (MDR) TB isolates. Methods: We sequenced the pncA, rpsA and panD genes and performed PZA susceptibility tests across 291 MDR-TB isolates to evaluate the performance of the sequencing method of these genes in detecting PZA resistance. Results: Results showed that 145 (90.0%) of 161 PZA phenotypic resistant isolates had mutations in pncA. Among the 16 isolates (10.0%) which did not have mutations in pncA, ten and three isolates had mutations in rpsA and panD, respectively. The sequencing method for detecting mutations in pncA alone had 90.1% (95% confidence interval (CI), 84.4–94.2) sensitivity and 92.3% (95% CI, 86.3–96.3) specificity. The combination of all three genes increased the sensitivity from 90.1% (95% CI, 84.4–94.2) to 98.1% (95% CI, 94.7–99.6) (p < 0.001) while the specificity remained unchanged. In 120 PZA-susceptible and 16 PZA-resistant isolates without pncA mutations, rpsA/panD mutations were correlated with PZA resistance. Conclusions: PZA resistance was largely associated with mutations in pncA. Mutations in rpsA and panD were also associated with PZA resistance in MDR isolates expressing wild-type pncA. The detection of mutations in pncA, rpsA and panD can be useful for the determination of PZA resistance.