大肠埃希菌碳青霉烯异质性耐药机制初步研究

Preliminary study of mechanisms of carbapenem heteroresistance in Escherichia coli

目的分析大肠埃希菌碳青霉烯异质性耐药的可能机制,为医院感染预防控制工作提供基础数据。方法收集深圳市第三人民医院、深圳市龙岗区人民医院、深圳市人民医院和中国科学院血液病医院2015年7月-2017年6月临床标本中筛选出的60株碳青霉烯异质性耐药大肠埃希菌(CHEC),采用改良Hodge实验检测菌株是否产碳青霉烯酶,PCR法检测菌株耐药基因,脉冲场凝胶电泳(PFGE)检测基因的同源性,并将菌株分型,同时通过菌落谱型分析实验(PAP)和亚群传代实验证实异质性耐药进化为完全耐药的过程。结果改良Hodge试验结果,60株CHEC中,20株产碳青霉烯酶,阳性率为33.33%,均携带耐药基因,17株为KPC型,3株为IMP型;随机选取17株CHEC进行PFGE分型,结果显示电泳图谱差异性较大;PAP结果显示,CHEC亚群经抗菌药物选择传代后,PAP曲线向右移动。结论医院筛选出的CHEC菌株无同源性,碳青霉烯异质性耐药的发生可能与CHEC菌株携带KPC、IMP等耐药基因有关,并且异质性耐药是完全耐药进化的中间阶段。

OBJECTIVE To explore the mechanisms of carbapenem heteroresistance in Escherichia coli strains so as to provide essential data for prevention and control of nosocomial infection.METHODS Totally 60 strains of Ec.oli with heteroresistance to carbapenem were collected from the clinical specimens of the Third People′s Hospital of Shenzhen,Longgang District People′s Hospital of Shenzhen,Shenzhen People′s Hospital and Chinese Academy of Sciences Hematology Hospital from Jul 2015 to Jun 2017.Carbapenemases were detected by using modified Hodge test,the drug resistance genes were detected by means of PCR,the homology of the genes was tested through pulsed-field gel electrophoresis(PFGE),the strains were typed,and the process of development from heteroresistance to complete drug resistance was verified by means of population analysis profile(PAP)test and subgroup passage experiment.RESULTS The result of the modified Hodge test showed that of the 60 strains of CHEC,20 were carbapenemase-producing strains,with the positive rate 33.33%,all of the strains carried with drug resistance genes,including 17 strains of KPC type and 3 strains of IMP type.17 strains of CHEC were randomly chosen for PFGE typing,and the result indicated that the electrophoresis patterns were quite different.The result of PAP showed that the PAP curve moved to the right after the antibiotics passage of CHEC subgroups.CONCLUSION There is no homology in the CHEC strains selected by the hospitals,the emergence of the carbapenem heteroresistance may be related to the drug resistance genes such as KPC and IMP carried by the CHEC strains,and the heteroresistance is at the intermediate stage of its evolution to complete resistance.