淋球菌对环丙沙星耐药机制的研究

Study on the mechanisms of resistance to ciprofloxacin in Neisseria gonorrhoea

目的:探讨淋球菌对环丙沙星耐药机制。方法:从临床分离株淋球菌,进行药敏试验,菌内聚积的环内沙星浓102度测定,聚合酶链反应()扩增和基因片段,产物作单链构象多肽性()分析检测其点突变,对PCRgyrAparCPCRSSCPPCR产物直接测序。结果:环丙沙星耐药株占,敏感性下降株占,敏感株占。敏感菌内聚积的环丙沙星浓度为72.5%20.6%6.9%,敏感性下降株和耐药株约为和。分析显示敏感性下降株和耐药菌株都存在点突变,经测序6ng/mg3ng/mg0.6ng/mgSSCPgyrA显示以第位氨基酸(GyrA91Ser→)和位(Phe95Asp→)双点突变常见,仅AsnMIC≥0.5μ的菌株才存在基因点突g/mlparC变,经测序显示以第位氨基酸ParC87(Ser→和位(Arg)104Cys→)双点突变常见。Tyr结论:作用靶位(和)的改变gyrAparC和膜耐药机制是淋球菌对环内沙星耐药的主要机制,促旋酶是环丙沙星主要作用靶位,基因突变与较高水平耐药有DNAparC关。

Objective: To explore mechanisms of resistance to ciprofloxacin in Neisseria gonorrhoea(NG). Methods: A total of 102 isolates were collected, antibiotic susceptibility tests performed ,accumulation of ciprofloxacin in isolates of NG was determined and gyrA and parC gene were amplified by PCR. The PCR products were assayed by SSCP. The PCR product which had the most common mutation was directly sequenced. Results: 72.5% were resistant to ciprofloxacin, 20.6% showed reduced susceptibility, 6.9% were susceptible and average accumulation of ciprofloxacin in the susceptible isolates was about 6ng/mg. However, in reduced-susceptiblity and rsistance isolates it was about 3ng/mg and 0.6ng/mg respectively. SSCP profiles revealed that the point mutations in gyrA gene occurred in all of isolates of reduced susceptibility and resistance, mutations (Ser-91→→Phe, Asp-95Asn) were most common, but the mutation points in parC gene only existed in the isolates which μ→→showed MIC 0.5g/ml. Double-point mutations(Ser-87Arg, Cys-104Tyr) were most common. Conclusion: The mechanisms of resistance to ciprofloxacin in NG were mainly involved in alteration of target molecules(GyrA and ParC) and resistance of membrane, and DNA gyrase was the main target molecule of ciprofloxacin, while the mutations in ParC were associated with high-level resistance to Ciprofloxacin quionolone.