1株犊牛源多重耐药大肠杆菌分离株的ESBLs与AmpCβ-内酰胺酶表型检测

Phenotypic Detection of ESBLs and AmpCβ-lactamases in One Multi-drug Resistant Escherichia coli Strain Isolated from a Calf

为了了解1株大肠杆菌分离株的耐药情况及超广谱β-内酰胺酶(ESBLs)与头孢菌素酶(AmpC)的耐药表型,从山西省某奶牛场因腹泻致死的1头犊牛肝脏中分离到1株优势大肠杆菌临床株,通过K-B纸片扩散法对该分离株进行了药物敏感性试验;并分别运用美国临床实验室标准化委员会(CLSI)推荐的双纸片协同法(DDST)和参照NCCLS2000药选规则而设计的阻抑物基法对该分离株进行了ESBLs与AmpCβ-内酰胺酶的表型确认试验;此外,还对该分离株质粒介导的blaTEM基因型进行了PCR检测。药物敏感试验结果显示,该大肠杆菌分离株对青霉素、阿莫西林、氨苄西林等20种抗生素产生耐药,对多黏菌素B、痢特灵和头孢西丁敏感,而对磷霉素、头孢曲松中度敏感;ESBLs与AmpCβ-内酰胺酶表型筛选结果显示,该分离株为兼产ESBLs与AmpCβ-内酰胺酶的阳性菌株;PCR检测结果显示,该分离株携带有质粒介导的blaTEM基因,检测到的该基因型与国内其他地区普遍流行的blaESBL基因型一致。该分离株为多重耐药性大肠杆菌菌株,且兼产ESBLs、AmpCβ-内酰胺酶;多黏菌素B、痢特灵和头孢西丁可作为治疗该场犊牛腹泻的首选药物。

To determine the drug resistance and phenotypes of ESBLs and AmpCβ-lactamases in an Escherichia coli strain,one dominant Escherichia coli clinical strain was isolated from liver of a calf died of diarrhea from a cattle farm in Shanxi province,antimicrobial susceptibility was tested by K-B disc diffusion method,and the phenotypic characterization of ESBLs and AmpCβ-lactamases was performed utilizing the double-disk synergy test(DDST)recommended by the Clinical and Laboratory Standards Institute(CLSI)and inhibitor-based method designed according to NCCLS2000,respectively.Moreover,plasmid-mediated blaTEM genotype in the isolated Escherichia coli strain was detected by PCR method.Antimicrobial susceptibility test(AST)showed that the isolated Escherichia coli strain was resistant to 20 kinds of antibiotics(penicillin,amoxicillin,ampicillin,etc.)completely,sensitive to polymyxin B,furazolidone and cefoxitin,and moderately sensitive to fosfomycin and ceftriazone.ESBLs and AmpCβ-lactamases phenotypic screening indicated that the isolated E.coli strain was an ESBLs and AmpC co-producing positve isolate.In addition,the result of PCR revealed that the isolated Escherichia coli strain harbored blaTEMgene in plasmids,and the detected blaTEMgenotype was in accord with blaESBLgenotypes commonly prevalent in other parts of China.This isolate was a multi-drug resistant(MDR)Escherichia coli strain,and co-produced ESBLs and AmpCβ-lactamases,simultaneously.Based on the results of AST,polymyxin B,furazolidone and cefoxitin will be the first choice for the treatment of calf diarrhea.