Purpose: This study was designed to identify the phenotypic and genotypic characteristics of pyrazinamide (PZA) resistance among multidrug-resistant Mycobacterium tuberculosis (MDR-TB) from Henan and to evaluate the efficacy of pncA, rpsA , and panD  mutations in predicting PZA resistance.
Materials and Methods: A total of 152 MDR strains were included in this study. The Bactec MGIT system was used to determine PZA susceptibility for all strains. The pncA, rpsA , and panD  genes were sequenced to identify any mutations, and the sequences were then aligned with the sequence of standard strain H37Rv. Moreover, the correlations between PZA-resistant phenotypes and treatment outcomes were analysed.
Results: Of the152 strains, 105 had a PZA-resistant phenotype, and 102 harboured the pncA  mutation. The PZA resistance rate was higher in the strains with resistance to all four first-line drugs and those that were pre-extensively drug-resistant (pre-XDR) and extensively drug-resistant (XDR). A total of 100 different pncA  mutation patterns were identified, including 80 point mutations and 20 insertions/deletions, and 32 new pncA  mutation patterns were detected. In this study, 13 strains had multiple mutations. Of the11 PZA-resistant strains without pncA  mutations, two harboured the rpsA  mutation, and one harboured the panD  mutation. With PZA susceptibility results as the reference, single-gene pncA  sequencing had sensitivity of 89.52% and specificity of 89.36%. With the combination of rpsA  and panD , the sensitivity increased to 92.38%, and the specificity remained the same. No significant differences were observed in the sputum smear/culture conversion rate between PZA-resistant patients and PZA-sensitive patients. However, PZA resistance was related to the time to sputum smear/culture conversion (P = 0.018).
Conclusion: The combination of pncA, rpsA , and panD  was beneficial for the timely diagnosis of PZA resistance and could provide a laboratory basis for customizing treatment regimens for MDR-TB patients.
Keywords: Mycobacterium tuberculosis , multidrug-resistant, pyrazinamide, pncA , rpsA , panD