title: Discrimination of enterohemorrhagic Escherichia coli (EHEC) from non-EHEC strains based on detection of various combinations of type III effector genes.
abstract: Enterohemorrhagic Escherichia coli (EHEC) strains comprise a subgroup of Shiga-toxin (Stx)-producing E. coli (STEC) and are characterized by a few serotypes. Among these, seven priority STEC serotypes (O26:H11, O45:H2, O103:H2, O111:H8, O121:H19, O145:H28, and O157:H7) are most frequently implicated in severe clinical illness worldwide. Currently, standard methods using stx, eae, and O-serogroup-specific gene sequences for detecting the top 7 EHEC serotypes bear the disadvantage that these genes can be found in non-EHEC strains as well. Here, we explored the suitability of ureD, espV, espK, espN, Z2098, and espM1 genes and combinations thereof as candidates for a more targeted EHEC screening assay. For a very large panel of E. coli strains (n = 1,100), which comprised EHEC (n = 340), enteropathogenic E. coli (EPEC) (n = 392), STEC (n = 193), and apathogenic strains (n = 175), we showed that these genetic markers were more prevalent in EHEC (67.1% to 92.4%) than in EPEC (13.3% to 45.2%), STEC (0.5% to 3.6%), and apathogenic E. coli strains (0 to 2.9%). It is noteworthy that 38.5% of the EPEC strains that tested positive for at least one of these genetic markers belonged to the top 7 EHEC serotypes, suggesting that such isolates might be Stx-negative derivatives of EHEC. The associations of espK with either espV, ureD, or Z2098 were the best combinations for more specific and sensitive detection of the top 7 EHEC strains, allowing detection of 99.3% to 100% of these strains. In addition, detection of 93.7% of the EHEC strains belonging to other serotypes than the top 7 offers a possibility for identifying new emerging EHEC strains.
authors.affiliation: Anses (French Agency for Food, Environmental and Occupational Health and Safety), Food Safety Laboratory, Maisons-Alfort, France.
authors.forename: Sabine
authors.initials: S
authors.lastname: Delannoy
authors.forename: Lothar
authors.initials: L
authors.lastname: Beutin
authors.forename: Patrick
authors.initials: P
authors.lastname: Fach
mesh_terms: D058947:Bacterial Secretion Systems / Q000235:genetics*; D001431:Bacteriological Techniques / Q000379:methods*; D054324:Enterohemorrhagic Escherichia coli / Q000145:classification* / Q000235:genetics* / Q000302:isolation & purification; D004927:Escherichia coli Infections / Q000382:microbiology; D029968:Escherichia coli Proteins / Q000235:genetics*; D005819:Genetic Markers; D006801:Humans; D012680:Sensitivity and Specificity
chemical_list: D058947:Bacterial Secretion Systems; D029968:Escherichia coli Proteins; D005819:Genetic Markers