Molecular characterization of pncA gene mutations in Mycobacterium tuberculosis clinical isolates from China

A sample of 35 pyrazinamide (PZA)-resistant and 30 PZA-susceptible clinical isolates recovered from Beijing and Taiyuan City, China were characterized by SSCP and sequence analysis for mutations in the pncA gene that encodes the Mycobacterium tuberculosis PZase. The purpose of this study was to understand the molecular basis and the characteristics of pncA gene mutations and its relation to PZA resistance in M. tuberculosis strains from China. Several mutations with base changes leading to amino acid substitutions were found in the PZA-resistant isolates. No mutations were seen in the 243 PZA-susceptible isolates. Among the 35 PZA-resistant isolates, 32 isolates (91.4 %) had nucleotide substitutions, insertions and deletions that resulted in amino-acid substitution; or frameshifts in some strains. Other previously uncharacterized mutations were found as follows: Asn118-->Thr, CG insertion at position 501; CC insertion at nucleotide position 403; a 8 base-pair deletion at start codon; Pro54-->Thr; AG insertion at 368; Tyr41-->His, Ser88-->stop, and A insertion at nucleotide position 301. IS6110 subtyping revealed that each strain was unique; indicative of the epidemiologic independence of the isolates.