Comparison between a bovine and a human enterohaemorrhagic Escherichia coli strain of serogroup O26 by suppressive subtractive hybridization reveals the presence of atypical factors in EHEC and EPEC strains.

Enterohaemorrhagic Escherichia coli (EHEC) strains are responsible for food poisoning in humans in developed countries via consumption of vegetal and animal foodstuffs contaminated by ruminant feces. The clinical conditions caused by EHEC strains vary from undifferentiated diarrhea to hemorrhagic colitis with, in a few cases, the appearance of the hemolytic uremic syndrome, which can lead to death. Most EHEC strains can be found in the gut of healthy ruminants, but some of the strains, belonging to O26, O111, O118 serogroups, for example, are also responsible for digestive disorders in calves. The aim of this research was to study the genomic differences between two EHEC strains of serogroup O26 isolated from a young calf and a human with diarrhea, to identify specific sequences of the bovine strain that could be implicated in initial adherence or host specificity. No sequence implicated in host specificity was found during our study. Finally, several factors, not usually present in EHEC strains of serogroup O26, were identified in the bovine strain. One of them, the PAI I(CL3) locus initially presented as a marker for LEE-negative VTEC strains, was found in 11.3% of EPEC and EHEC strains.