马鞍山市非典型肠致病性大肠杆菌的鉴定及分子分型研究

Identification and molecular typing of atypical enteropathogenic E. coli strains in Maanshan city

目的通过常规鉴定方法和分子分析手段,了解马鞍山市非典型肠致病性大肠杆菌(a EPEC)的表型特征、菌株携带的eae基因型别及多位点序列分型(MLST)特征。方法病原学表型特征采用生化鉴定、血清学分型、药敏试验;分子生物学分析采用16s r DNA基因测序、PCR检测毒力基因、eae基因测序比对分型及MLST分型。结果 8株a EPEC测试菌生化特点与普通大肠埃希菌一致,1株菌产生H2S无法鉴定。1株菌为O26:K60,其余8株菌的血清学无法分型。药敏结果显示,44%仅耐氨苄西林,22%耐氨苄西林/舒巴坦和SMZ,其余均敏感。所有测试菌均为大肠杆菌,所有测试菌均携带uid A、eae基因而不携带stx1和stx2基因,均为a EPEC菌株。4株菌的eae基因无法分型,其余5株菌分别β1、β2、ε、ι1和ι2型。9株菌共产生6种ST型。结论马鞍山的a EPEC分离株的分子生物学特征呈现多样性,没有相对集中的遗传克隆群。

Objective The aim of this study was to investigate the phenotypic and molecular features of atypical enteropathogenic Escherichia coli （ aEPEC ） isolates in Maanshan city. Methods The phenotypic characteristics of aEPEC strains were analyzed by biochemical identification, serological typing and drug sensitivity test, and the molecular features were examined by 16s rDNA sequencing, virulence genes detection, eae gene subtyping and multilocus sequence typing （ MLST）. Results The biochemical identification showed that eight isolates were E. coli, but one strain producing H2S couldnt be determined. One isolate was O26：K60, while the other strains were untypable by serological typing. For antimicrobial susceptibility, all of the 9 strains were sensitive to the antimicrobials tested, of them,4 strains were resistant to ampicillin and 2 strains were resistant to ampicillin/sulbactam and SMZ. The sequencing analysis of 16s rDNA genes showed that all of the 9 strains were E. coli. All 9 strains were uidA ^＋ , eae ^＋ , stxl ^- and stx2^ -. Four aEPEC strains were non - typable for intimin and five intimin subtypes （ β1, β2, 8, ι1 and ι2） were identified in the other five strains. Altogether, 6 different STs were identified. Conclusion A high degree of heterogeneity of molecular features was observed among the aEPEC isolates in Maanshan city.