1株携带qnrB4及aac(6′)-Ⅰb-suzhou型基因同时产ESBLs、AmpC酶多药耐药大肠埃希菌的调查

Investigation of one strain of ESBLs and AmpC-producing multidrug-resistant Escherichia colicarrying qnrB4 and aac(6′)-Ⅰb-suzhou

目的了解1株产ESBLs、AmpC酶大肠埃希菌的耐药机制。方法采用纸片扩散法检测1株大肠埃希菌对19种抗菌药物的敏感性,采用聚合酶链反应(PCR)检测6种耐药基因:qnrA、qnrB、qnrC、qnrS、qepA、aac(6′)-Ⅰb,并对qnrB、aac(6′)-Ⅰb基因测序后进行BLAST比对分析。结果该菌株除对碳青霉烯类、酶抑制剂复合抗菌药物类敏感外,对其余药物均耐药;PCR发现该菌株同时携带qnrB和aac(6′)-Ⅰb,经测序并分别与已在美国国立信息中心登录的DQ303921(qnrB4)和EF375621[aac(6′)-Ⅰb-suzhou]型比对,同源性均>99.0%。结论该菌株多药耐药的机制与产ESBLs、AmpC酶及携带qnrB4和aac(6′)-Ⅰb基因有关;该研究是第一篇从1株产ESBLs、AmpC酶大肠埃希菌中检出同时携带qnrB4和aac(6′)-Ⅰb-suzhou型基因的报道。

OBJECTIVE To understand resistant mechanisms of a Escherichia coli strain from blood carrying qnrB4,aac（6′）-Ⅰb-suzhou type genes and producing ESBLs,AmpC.METHODS The susceptibility of a strain of E.coli isolated from the blood to seventeen antibiotics were detected by Kirile-Baure method.Six genes（qnrA,qnrB,qnrC,qnrS,qepA,aac（6′）-Ⅰb） were identified by polymerase chain reaction（PCR）and confirmed by sequencing and compared with that by BLAST.RESULTS The studied strain was multi-drug resistant to all except for carbapenems and complex antibiotics that contained enzyme inhibitors;qnrB,aac（6′）-Ⅰb genes were detected after being sequenced and compared with DQ303921（qnrB4）,EF375621（aac（6′）-Ⅰb-suzhou）type that were registered in the National Biological Information Center.The homology was greater than 99.0%.CONCLUSION The mechanisms of this multi-drug resistant E.coli are mainly related to the production of ESBLs,AmpC enzymes and carrying of qnrB4,aac（6′）-Ⅰb genes.This is the first report that one strain of E.coli carries both qnrB4 and aac（6′）-Ⅰb-suzhou type genes.