肠杆菌科耐第三代头孢菌素临床株中ISCR1元件与ESBLs基因的关系

Relation between ISCR1 and ESBLs gene in third generation cephalosporinresistant clinical strains of Enterobacteriaceae

摘要:

目的了解某地区肠杆菌科耐第三代头孢菌素临床株中携带新型可移动遗传元件插入序列共同区域(ISCR1)的情况及其与超广谱β内酰胺酶（ESBLs）基因的关系。方法以最低抑菌浓度（MIC）法检测细菌耐药表型；双纸片扩散法进行ESBLs确证试验；聚合酶链反应（PCR）、单链PCR构象的多态性（PCRSSCP）、DNA序列分析检测ISCR1基因和SHV、TEM、CTXMESBLs基因；PCRmapping检测ISCR1与ESBLs基因的关系。结果83株肠杆菌科耐第三代头孢菌素临床株中，17株携带ISCR1元件。携带ISCR1元件的菌株中，2株大肠埃希菌（EA791、EA1367）、3株阴沟肠杆菌（EC1322、EC1342、EC553）及1株产酸克雷伯菌K386临床株ESBLs确证试验阳性，其中EA791、EC553及K386携带CTXM1组ESBLs基因；EA1367同时携带CTXM1组和CTXM9组ESBLs基因；EC1322、EC1342携带SHV12型 ESBLs基因；6株细菌均携带TEM型基因，经PCRSSCP分析显示均为TEM 1，但经PCRmapping显示其ISCR1元件下游未连接ESBLs基因。结论该地区耐第三代头孢菌素临床株中存在ISCR1元件，尚未发现菌株携带的ISCR1元件与ESBLs 基因的直接联系，此元件可能参与其他耐药基因的水平传播。

Abstract:

ObjectiveTo study the distribution of insertion sequence common region1(ISCR1) in local third generation cephalosporinresistant clinical strains of Enterobacteriaceae and the relationship between ISCR1 and ESBLs.MethodsAntimicrobial susceptibilities were tested by microdilution broth method;  ESBLs phenotypic confirmatory test were performed by double disk diffusion method; ISCR1 gene, SHV,TEM, and CTXMESBLs genes were amplified by PCR and analysed by singlestrand conformation polymorphism (PCRSSCP) and DNA sequencing , and the relationship between ISCR1 and ESBLs gene was detected by PCRmapping.ResultsAmong 83 strains , 17 isolates habored ISCR1 gene,6 of which were  positive  in ESBLs phenotypic confirmatory test,including 2 Escherichia coli strains（EA791,EA1367）,3 Enterobacter cloacae （EC1322,EC1342,EC553） , and 1 Klebsiella oxytoca (K386),  EA791,EC553 and K386 all contained CTXM1 ESBLs gene; EA1367 contained  both CTXM1 and CTXM9 group ESBLs gene ;EC1322 and EC1342 both contained SHV12 ESBLs gene; all  6 strains carried TEMESBL gene which were verified by PCRSSCP. PCRmapping revealed that there’s no relation between ISCR1 and ESBLs gene. ConclusionISCR1 element exist in local third generation cephalosporinresistant clinical strains of Enterobacteriaceae, the study found no evidence of direct relationship between ISCR1 and ESBLs, the element maybe play a role in horizontal transmission of other drugresistant genes.