Abstract: Objective To identify the genus, species, and type of a bacterial strain (X175) isolated from a rodent of natural death.Methods The species and genus of X175 were identified based upon 16S rDNA sequencing. Real-time PCR was used in the detection of toxin genes commonly detected in diarrheagenic Escherichia coli(stx1/stx2/eae, lt/st, aggR/ipaH) and genes of E. coliO104 gene and H4 gene. Nine virulence genes ofenterohemorrhagicE. coli(EHEC) O104∶H4 were detected by PCR.Results The 16S rDNA sequence of X175 strain was 99% homogeneous to that of strains ofE.spp., and was most closely related toE. coliO104∶H4 in phylogenetic analysis.E. coliO104 gene andipaH were detected, whilestx1/stx2/eae, lt/st, aggR,Shigella/Salmonella, and E. coli H4 gene were not. None of the 9 virulence genes of EHEC O104∶H4 was detected.Conclusion X175 is an attenuated strain ofE. coliO104. H antigen and some other features remain to be further studied.

Key words: Escherichia coli, 16S rDNA, Virulence gene

摘要： 目的 对1株由自毙鼠分离的细菌(X175菌株)进行属、种及型的鉴定。方法 ①采用16S rDNA对X175菌株进行种属鉴定;②应用荧光PCR检测X175菌株是否存在致泻性大肠埃希菌常见毒素基因(stx1/stx2/eae、lt/st、aggR/ipaH)及大肠埃希菌O104、H4基因;③应用PCR检测X175菌株是否存在肠出血性大肠埃希菌(EHEC)O104∶H4的9个毒力基因。结果 ①经16S rDNA鉴定,X175菌株与大肠埃希菌埃希菌属的一些菌株相似度达99%,进化树显示X175菌株与大肠埃希菌O104∶H4菌株的亲缘关系较近;②大肠埃希菌O104基因和ipaH基因检测结果均为阳性,stx1/stx2/eae、lt/st、aggR、志贺菌/沙门菌、H4等基因检测结果均为阴性;③肠出血性大肠埃希菌O104∶H4九个毒力因子检测结果均为阴性。结论 X175菌株为大肠埃希菌O104弱毒型菌株,H抗原和其他一些特性还需进一步研究。

关键词: 大肠埃希菌, 16S rDNA, 毒力基因