阴沟肠杆菌的耐药性及对喹诺酮类耐药基因的检测

Study on drug resistance of Enterobacter cloacae and detection its quinolone-resistant genes

目的研究临床分离的阴沟肠杆菌的耐药性和其对喹诺酮类抗生素耐药的分子机制。方法采用VITEK2型全自动微生物检测系统鉴定临床分离的细菌,用K-B法测定阴沟肠杆菌对25种抗生素的敏感性,用聚合酶链反应检测耐环丙沙星的阴沟肠杆菌质粒介导的喹诺酮类耐药基因,包括qnrS、qnrA、qnrB、qepA和aac(6’)-Ib,并对阳性的aac(6’)-Ib结果进行测序分析。结果 71株阴沟肠杆菌对环丙沙星和左氧氟沙星的耐药率分别为46.5%和40.8%,对第一、二、三代头孢菌素类药物的耐药率在50%以上,对青霉素类药物的耐药率在70%以上,对含β-内酰胺酶抑制剂复合物的耐药率在50%以上,对氨基糖苷类药物(庆大霉素、妥布霉素)的耐药率在46.5%以上,对碳青霉烯类药物的敏感性最好,对亚胺培南、美罗培南的耐药率为0。37株耐环丙沙星的阴沟肠杆菌中1株检出qnrA基因(2.7%),4株检出qnrS基因(10.8%),qnrB基因全阴性,qnr基因的总阳性率为13.5%。2株检出qepA基因(5.4%)。25株检出aac(6')-Ib基因(67.6%),经测序证实其中5株为aac(6')-Ib-cr(13.5%)。1株菌同时携带qnrS和aac(6')-Ib-cr基因。质粒介导的喹诺酮类耐药基因的总携带率为29.7%。结论临床分离的耐喹诺酮类药物的阴沟肠杆菌携带qnrA、qnrS、qepA和aac(6')-Ib-cr基因,未检出qnrB。qnr、qepA和aac(6')-Ib-cr基因引起质粒介导的阴沟肠杆菌对喹诺酮类抗生素的耐药。

Ahn To study drug-resistance to antibiotocs and detect quinolones resistant genes in clinical isolates of Enterobacter cloacae, and study the molecular resistant mechanism. Methods The clinical isolates were identified by the automatic VITEK 2 system and their antimicrobial susceptibility were tested by K-B disc diffusion. The quinolones resistant genes including qnrS、qnrA,qnrB、qepA and aac （6＂）-Ib were analyzed by polymerase chain reaction. DNA sequencing was used for identification of aac（6＂）-Ib-cr. Results In 71 Enterobacter cloacae isolates,the resistant rates to ciprofloxacin and levofloxacin were 46.5% and 40.8%, respectively. The resistant rates to cephalosporin, penicillins, 13-1actarrdl3-1actamase inhibitor combinations, aminoglycosides were over 50%, 70%, 50%, 46.5%, respectively. The resistant rates to imipenem and meropenem were 0%. Of 37 Enterobacter cloacae isolates resisted to ciprofloxacin, the positive rate of qnrS, qnrB, qnrA, qepA and aac （6＂）-Ib gene was 10.8% ,0% ,2.7% ,5.4% ,67.6% ,respectively. The total positive rate of qnr was 13.5%. By sequence analysis,5 of 25 aac（6＂）-Ib positive genes were aac（6＂）-Ib-cr,the positive rate was 13.5%. qnrS and aac（6＂）- Ib-cr gene were identified in one isolate. The positive rate of plasmid-mediate quinolones resistant gene in Enterobacter cloacae resistant to ciprotloxacin was 29.7%. Conclusion Enterobacter cloacae resistant to ciprofloxacin might carry qnrA,qnrS,qepA and aac （6＂）-Ib-cr gene. qnrB gene were not found, qnr,qepA and aac （6＂）-Ib-cr might be the mechanisms of plasmid-mediated quinolones resisitance in Enterobacter cloacae.