中文摘要：

oqxAB是近年新发现的一种可同时介导细菌对喹口恶啉类药物、氯霉素和喹诺酮类等抗菌药物耐药的多重耐药外排泵。本研究拟比较oqxAB基因在不同来源动物大肠杆菌中的流行情况,并分析oqxAB对耐药性的影响。采用PCR法对2007—2009年主要分离自广东地区的655株大肠杆菌,包括猪源219株、牛源40株、鸭源205株及鸡源191株,进行oqxAB基因的检测,并采用琼脂稀释法测定大肠杆菌对10种抗菌药物的敏感性。oqxAB在猪、牛、鸭、鸡源大肠杆菌的阳性率分别为49.3%（108/219）、47.5%（19/40）、60.5%（124/205）和12.6%（24/191）,总阳性率为42.0%（275/655）。大肠杆菌对庆大霉素、氨苄西林、复方新诺明、恩诺沙星和四环素耐药率较高,分别达到68.2%、68.7%、70.4%、77.9%和80.8%。oqxAB阳性菌和阴性菌对头孢曲松、四环素和复方新诺明的耐药率差别不显著（P〉0.05）,对庆大霉素的耐药率差别显著（P〈0.05）,对氨苄西林、环丙沙星、阿米卡星、氯霉素、氟苯尼考和恩诺沙星的耐药率oqxAB阳性菌极显著高于阴性菌（P〈0.01）。中国兽医临床oqxAB流行很普遍,这可能与国内大量使用喹口恶啉类药物有关。

英文摘要：

The oqxAB multidrug efflux pump,which confers high resistance to quinoxaline chloramphenicol and ampicillin,was discovered recently.This study investigated the prevalence of the oqxAB among Escherichia coli isolated from different origins and analysed the influence on resistance.A total of 655 strains were isolated in Guangdong province from 2007 to 2009,including 219 from swine,40 from bovine,205 from duck and 191 from chicken.All of the strains were screened for oqxAB gene by PCR.Susceptibility to 10 antimicrobial agents were determined by agar disc diffusion method.About 49.3%（108/219） Escherichia coli isolates from swine,47.5%（19/40） from bovine,60.5%（124/205） from duck,and 12.6%（24/191） from chicken were positive for oqxAB.The overall proportion of isolates harboring oqxAB was 42.0%（275/655）.The isolate showed high rate of resistance to gentamicin,ampicillin,trimethoprim/sulfamethoxazole,enrofloxacin,tetracycline,reaching 68.2%,68.7%,70.4%,77.9%,80.8%,respectively.The resistance rate of ceftriaxone,tetracycline and trimethoprim/sulfamethoxazole had no significant effect between oqxAB-positive and negative（P0.05）.The oqxAB had significant effects on gentamicin（P0.05） and had extremely significant effect on ampicillin,ciprofloxacin,amikacin,chloramphenicol,florfenicol and enrofloxacin（P0.01）.The prevalence of oqxAB is very common in China,which may be due to the overuse of quinoxaline.