The epidemiology and gene mutation characteristics of pyrazinamide-resistant <i>Mycobacterium tuberculosis</i> clinical isolates in Southern China

This study investigates the epidemic trend of pyrazinamide (PZA)-resistant tuberculosis in Southern China over 11 years (2012–2022) and evaluates the mutation characteristics of PZA resistance-related genes (<i>pncA, rpsA,</i> and <i>panD</i>) in clinical <i>Mycobacterium tuberculosis</i> (<i>M. tuberculosis</i>) isolates. To fulfil these goals, we analyzed the phenotypic PZA resistance characteristics of 14,927 clinical isolates for which Bactec MGIT 960 PZA drug susceptibility testing (DST) results were available, revealing that 2,054 (13.76%) isolates were resistant to PZA. After evaluating the annual variation in the PZA resistance rate among tuberculosis cases in this region, it was observed that it decreased from 37.21% to 6.45% throughout the initial 7 years (2012–2018) and then increased from 8.01% to 12.12% over the subsequent 4 years (2019–2022). Sequences of <i>pncA</i> were obtained from 402 clinical <i>M. tuberculosis</i> complex isolates. For <i>rpsA</i> and <i>panD,</i> sequences were obtained from 360 clinical <i>M. tuberculosis</i> complex isolates. Mutations in <i>pncA</i> were found in 8 out of 223 PZA-sensitive isolates (3.59%) and 105 of 179 (58.66%) PZA-resistant isolates. Conversely, non-synonymous mutations in <i>rpsA</i> were identified in 5 of 137 (3.65%) PZA-resistant isolates, whereas the mutation ratio of <i>rpsA</i> among PZA-sensitive isolates was high at 14.03% (31/221). This difference in the <i>rpsA</i> mutation rate was statistically significant (<i>P = 0.001</i>, chi-square test). No <i>panD</i> mutations were observed in the 137 PZA-resistant isolates, whereas two PZA-sensitive isolates harboured point mutations in <i>panD</i>, including one nonsense mutation (C433 T) and another C-69 T mutation. These findings indicate that <i>rpsA</i> and <i>panD</i> may not significantly contribute to the development of PZA resistance in clinical <i>M. tuberculosis</i> isolates.