Associations between virulence factors of Shiga toxin-producing Escherichia coli and disease in humans

Associations between known or putative virulence factors of Shiga toxin-pro ducing Escherichia coli and disease in humans were investigated. Univariate analysis and multivariate logistic regression analysis of a set of 237 iso lates from 118 serotypes showed significant associations between the presen ce of genes for intimin (eae) and Shiga toxin 2 (stx(2)) and isolates from serotypes reported in humans. Similar associations were found with isolates from serotypes reported in hemorrhagic colitis and hemolytic-uremic syndro me. The enterohemorrhagic E. coli (EHEC) hemolysin gene was significantly a ssociated with isolates from serotypes found in severe diseases in univaria te analysis but not in multivariate logistic regression models. A strong as sociation between the intimin and EHEC-hemolysin genes may explain the lack of statistical significance of EHEC hemolysin in these multivariate models , but a true lack of biological significance of the hemolysin in humans or in disease cannot be excluded. This result warrants further investigations of this topic. Multivariate analysis revealed an interaction between the ea e and stx(2) genes, thus supporting the hypothesis of the synergism between the adhesin intimin and Shiga toxin 2. A strong statistical association wa s observed between the stx(2) gene and severity of disease for a set of 112 human isolates from eight major serotypes. A comparison of 77 isolates of bovine origin and 91 human isolates belonging to six major serotypes showed significant associations of the genes for Shiga toxin 1 and EspP protease with bovine isolates and an increased adherence on HEp-2 cell cultures for human isolates, particularly from diarrheic patients and healthy persons.