Model for evaluation of pathogenicity of extra-intestinal pathogenic Escherichia coli

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Total 501 Escherichia coli isolates were collected in this study, and were analyzed by using multi locus sequence typing method (MLST). As a result, 85.9% of extraintestinal pathogenetic E. coli (ExPEC) belonged to group B2, while among commensal E. call isolates, more than half were group A/B1, and 40.2% of the isolates belonged to group B2.Based on the results of MLST analysis, group B2 isolated divided into eight sub-groups. However the isolates from the B2 subgroup did not show any significant differences on growth capacity in urine, introducing ability of IL6, and adhesive potential to epithelial cells in vitro, which are suggested as virulence characters for ExPEC.Recently it is reported that cdiA gene has a contact bactericidal activity, and the cdiA might play a role for competition with other bacteria in human intestine. Among E. call isolates from acute cystitis, 57.8% of the isolates encoded the cdiA homologue, and the cdiA widely distributed in all subgroups of group B2 as well as A/B1 and D groups. The cdiA gene was known to be associated with pathogenicity islands (PAIs) encoding papGIII and hlyA. We could show genetic variation between these PAIs, which encoded papGIII, hlyA and cdiA.To investigate which type of E. coli on phylogeny is dominant in human intestine, we collected commensal E. coil form stool of healthy volunteers. During analysis of commensal E coli on genotype and phylogeny, we found out that a certain B2-8 strain was isolated from some healthy volunteers for more than half-year as the dominant strains, indicating that this strain has a potential to adjust for the environment. As this strain did not have the cdiA, this fact implied that another mechanism might provide ability to the strains as a dominant residence in the human intestine. We need to perform further analysis for investigating mechanisms on competitive growth inhibition in the human intestine.