This study was designed to investigate the presence of mutations in the pncA gene, minimum inhibitory concentrations and pyrazinamidase activity of pyrazinamide-resistant Mycobacterium tuberculosis. In total, 47 M. tuberculosis clinical isolates from a local region of China were assayed. Pyrazinamidase activity was measured by pyrazinamide deamination to pyrazinoic acid and ammonia, and a 721 bp region, including the entire pncA open-reading frame, 104 bp of the upstream sequence and 59 bp of the downstream sequence, was determined by DNA sequencing of purified polymerase chain reaction products. Of the 47 isolates resistant to pyrazinamide, 44 lost pyrazinamidase activity and had pncA mutations that occurred mainly near pyrazinamidase's active or metal ion binding sites; nine of them have not been reported previously. Three pyrazinamide-resistant isolates carried the wild-type pncA sequence and retained pyrazinamidase activity. These results show the molecular mechanism of pyrazinamide resistance in China and may also contribute towards the prevention of tuberculosis in China.
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