On pig farms with Shiga toxin producing F18+ Escherichia coli (STEC) infections, oedema disease and mortality occur in ± 20 % of infected pigs. Similar figures are seen in humans infected with Shiga toxin producing enterohemorraghic E. coli. In this project we identified some factors which play a role in the disease variation between infected animals, such as bile acids and some antibiotics. This knowledge will be used to increase or decrease toxin production by STEC strains. A porcine small intestinal segment perfusion model will be used to optimize conditions that lead to subclinical infections. These conditions will allow to develop an in vivo subclinical infection model in which we can analyze if parenteral and or oral vaccination can improve pig health and replace antibiotic treatment.