烧伤创面耐药金黄色葡萄球菌的分离及其norA基因突变分析

Isolation of the drug-resistant Staphylococcus aureus strains from burn wound flora and analysis of norA genetic mutation

目的探讨野生型耐药金黄色葡萄球菌的nora基因及其启动子的突变情况。方法分离并筛选出10株烧伤创面的耐药性金黄色葡萄球菌，对norA基因及其启动子进行测序并分析其改变。结果共分离出金黄色葡萄球菌87株，它们对万古霉素100％敏感，对奎奴普汀和呋喃妥因也有很高的敏感性，而对其余抗生素的耐药率则非常高；耐甲氧西林金黄色葡萄球菌（MRSA）的阳性率达到91．7％。所有10株实验菌的nora基因编码区都有1349位G→A的点突变，也就是氨基酸的291位处存在Gly（甘氨酸）→Asp（天冬氨酸）的突变。利血平逆转实验提示10株细菌对三种抗生素的MICs值均存在不同程度的下降。结论norA基因突变是金黄色葡萄球菌耐药的机制之一。

Objective To investigate the genetic mutation of the nora gene and its promotor from the wild-type drug-resistance Staphylococcus aureus （S. aureus） strains. Methods A total of 10 antibiotic-resistant S. aureus strains were isolated and screened from the burn wound for the sequencing and analysis of the norA gene and its promoter. Results There isolated 87 S. aureus strains from the burn wound flora, which were completely sensitive to vacomycin, highly sensitive to Qninupristin and Nitrofurantoin, but highly resistant to the other antibiotics, even up to 91.7% of MRSA. There found the same point mutation （G→A） located at 1 349 sites of the nora gene coding region in all the S. aureus strains, saying that the amino acid was changed from Gly （glycin） to Asp （aspartic acid） in 291 sites. The reserpine reverse test showed that the MICs value of three antibiotics was lowered at various degrees in all 10 strains. Conclusion NorA gene mutation is one of the mechanisms for antibiotic-resistance of S. aurens.