粪肠球菌Ⅱ型拓扑异构酶QRDR基因突变与耐氟喹诺酮类药物关系的研究

Study of the relationship between Enterococcus faecalis type Ⅱ topoisomerase QRDR gene mutations and fluoroquinolone resistance

目的检测临床分离的粪肠球菌对6种氟喹诺酮类药物的敏感性,研究粪肠球菌II型拓扑异构酶基因突变与对氟喹诺酮类药物耐药性的关系,以了解粪肠球菌对氟喹诺酮类药物的耐药机制。方法采用CLSI M7-A8方案推荐的琼脂稀释法检测临床分离的112株粪肠球菌对6种氟喹诺酮类药物的MIC;筛选出环丙沙星耐药株,PCR扩增其gyrA、gyrB,parC和parE基因的喹诺酮耐药决定区(QRDR),并与标准敏感株核苷酸序列进行比较,分析基因突变与耐药的相关性。结果 6种FQs药物对112株粪肠球菌的抗菌活性(MIC50,MIC90)从强到弱依次为:莫西沙星>加替沙星>左氧氟沙星>环丙沙星、氧氟沙星>诺氟沙星。5株耐环丙沙星粪肠球菌的II型拓扑异构酶QRDR基因都发生了突变:有4株的gyrA基因QRDR发生了点突变,其中3株表现为Ser83→Ile(AGT→ATT),1株表现为Glu87→Gly(GAA→GGA),4株parC基因QRDR发生突变,突变方式为Ser80→Ile(AGC→ATC),gyrB和parE基因未发现突变。

Objective To detect the sensitivity of clinical isolated E. faecalis to 6 kinds of fluoroquinolones and research the relationgship between type II topological isomerase gene mutations of E. faecalis and the fluoroquinolones resistance. Methods Using agar dilution method to detect the MIC of 6 kinds of fluoroquinolones of 112 stains E. faecalis. Screened ciprofloxacin drug-resistant strains, applicate PCR method to amplify QRDR of gyrA, gyrB, parC and parE genes, and analyzing the relevance of the genetic mutation and resistance. Results MICs0 and MIC90 of 6 FQs on 112 E. faecalis from strong to the weak as follows： MOX 〉GAT 〉 LVX 〉 CIP, OFX〉 NOR. All of 5 strains of CIP resistance E. faecalis QRDR were mutated： 4 strains gyrA gene mutations occur, including 3 strains Ser83→Ile （AGT→ATT）, 1 strain Glu87→Gly （GAA→GGA）, 4 strains parC gene Ser80→Ile way （AGC→ATC）; gyrB andparE genes had not found mutations.