对氨水杨酸钠耐药与结核分枝杆菌胸苷酸合成酶基因突变的研究

目的检测结核分枝杆菌临床分离株对氨水杨酸钠（PAS）耐药和胸苷酸合成酶（thyA）基因突变的关系，探讨结核分枝杆菌PAS耐药的分子机制。方法95株结核分枝杆菌临床分离株中的51株PAS敏感株和44株PAS耐药株的PAS耐药相关基因thyA基因进行PCR扩增，扩增产物纯化后进行序列测定，与结核分枝杆菌标准株H37Rv的野生型thyA基因序列进行比对，判断这些临床分离株thyA基因有无突变。结果51株PAS敏感株thyA基因未检出突变，44株PAS耐药株中有16个临床分离株的thyA基因检测到突变，突变检出率为36．4％（16／44）。突变类型包括置换、颠换、插入、缺失，均为单碱基改变或单碱基缺失，其中2株为thyA基因2个位点联合突变。结论结核分枝杆菌thyA基因突变是其产生PAS耐药的重要原因之一。结核分枝杆菌胸苷酸合成酶是PAS作用的重要靶位。

Mutations in the thymidylate synthase gene is a major mechanism in the para-aminosalicylic acid resistance of M. tuberculosis

OBJECTIVE: The mechanisms of resistance to para-aminosalicylic acid (PAS) are undefined. In this study, we explored the mechanisms of M. tuberculosis PAS resistance in clinical isolates. METHOD: The whole sequence of thymidylate synthase (thyA) gene encoding thyA genes was sequenced in 51 para-aminosalicylic acid (PAS)-sensitive and 44 resistant M. tuberculosis clinical isolates. RESULTS: Sixteen of 44 resistant M. tuberculosis clinical isolates had mutations in the thyA genes, a mutation rate of 36.4% (16/44). No mutations were detected in the sensitive clinical isolates. The mutation types included substitutions, conversions and deletions. CONCLUSIONS: Mutations in the thyA gene is associated with PAS resistance in M. tuberculosis clinical isolates, and mutations in thyA gene probably represent a major mechanism of developing resistance to the drug. Thymidylate synthase is likely to be the target of PAS action.