Identification of Genetic Markers for Differentiation of Shiga Toxin-Producing, Enteropathogenic, and Avirulent Strains ofEscherichia coliO26

Author:

Bugarel Marie,Beutin Lothar,Scheutz Flemming,Loukiadis Estelle,Fach Patrick

Abstract

ABSTRACTShiga toxin-producingEscherichia coli(STEC) O26 is one of the top five enterohemorrhagicE. coli(EHEC) O groups most often associated with hemorrhagic colitis and hemolytic uremic syndrome (HUS) worldwide. STEC O26 is considered to have evolved from enteropathogenic (EPEC) O26 strains through the acquisition of Shiga toxin (Stx)-encoding genes. Our PCR data identified several STEC-like strains expressing all features of STEC except Stx production and carrying remnants of Stx phages that were probably derivatives of EHEC O26. EHEC and EPEC O26 strains phenotypically resemble O26 EHEC-like and apathogenicE. coliO26 strains and are therefore undistinguishable by cultural methods. A clear discrimination between the different O26 groups is required for diagnostics in patients and for control of food safety. To develop an assay for specific detection of EHEC and EHEC-like O26 strains, we used a high-throughput PCR approach for selection of discriminative genetic markers among 33 tested genes mostly encoding type III secretion system effector proteins. The genesECs1822,nleH1-2,nleA,nleC,nleH1-1,nleG,nleG2,nleG6-1,nleG6-2,espJ,espM2,nleG8-2,espG,ent(orespL2),nleB,nleE,efa1, andespBwere detected at different frequencies in O26 EHEC, EHEC-like, and EPEC strains, indicating the possible role of these genes in virulence of human pathogenic O26 strains. TheespKandespNgenes were detected only in EHEC and EHEC-like O26 strains.espKwas present in 99.14% of EHEC and 91.14% of EHEC-like O26 strains and was hence the best candidate as a genetic marker for characterizing these pathogroups. These data were corroborated by a genotyping real-time PCR test based on allelic discrimination of thearcA(aerobic respiratory control protein A) gene. The results indicate that a combination of molecular detection tools for O26wzx(wzxO26),eae-beta,stx,espK, andarcAgenotyping is highly discriminative for clear identification of EHEC and EHEC-likeE. coliO26 strains. This simple diagnostic test might be applicable in hospital service laboratories or public health laboratories to test strains isolated from stools of patients suffering from diarrhea.

Publisher

American Society for Microbiology

Subject

Ecology,Applied Microbiology and Biotechnology,Food Science,Biotechnology

Reference45 articles.

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