临床分离纹带棒状杆菌喹诺酮类耐药株gyrA和parC基因突变的研究

Relationships between gyrA,parC genes and resistance of Corynebacterium striatum to quinolones

目的探讨gyrA、parC基因的改变与纹带棒状杆菌耐喹诺酮类抗生素的关系。方法采用微量稀释法测试纹带棒状杆菌对环丙沙星、左旋氧氟沙星、万古霉素的敏感性。PCR扩增检测gyrA和parC基因喹诺酮类耐药决定区相关片段并测序,在GenBank中进行Blast及BlastX分析并观察氨基酸突变位点,用NcoI酶进行PCR-RFLP。结果 37株纹带棒状杆菌对环丙沙星和左旋氧氟沙星的耐药率为94.6%,30株菌发生双突变(87位Ser突变为phe,91位Asp突变为Ala),5株菌单点突变(87位Ser突变为phe)。PCR-RFLP经NcoI酶切后显示,敏感株和耐药株均产生3个条带。结论纹带棒状杆菌对环丙沙星、左旋氧氟沙星的耐药率较高,对万古霉素全部敏感。纹带棒状杆菌对喹诺酮类抗生素的耐药机制主要是gyrA突变引起的,尤以双突变占优势。纹带棒状杆菌不携带parC基因,不编码拓扑异构酶IV。

Objective To investigate the relationships between gyrA,parC genes and resistance of Corynebacterium striatum to quinolone antibiotics.Methods The quinolone resistance determining region(QRDR) of the gyrA and parC genes of C.striatum were amplified.The sequences and mutations of gyrA and parC genes were analyzed in GenBank by Blast and BlastX.Results The resistance rates of C.striatum to ciprofloxacin and Levofloxacin were 94.6%.Thirty strains presented a double mutation at positions 87 and 91,with a change from Ser to Phe in the amino acid codon 87 and from Asp to Ala at position 91.Five strains presented a mutation at position 87.Conclusion The resistance rates of C.striatum to antibiotics are high.These strains are sensitive to Vancomycin.The mutation of gyrA gene is the reasons of the resistance of C.striatum to quinolones,especially double mutation.C.striatum lacks the parC gene and does not encode topoismerase IV.