Risk assessment of STEC/stx-bacteriophages as zoonotic agents in the food production

STEC is a major cause of gastrointestinal diseases in humans and their main virulence factor is the ability to produce shiga toxin (Stx), which is encoded on bacteriophages. The present study is a follow-up of the PhD-work done by the applicant, where it was shown that sheep and cattle in Norway are a reservoir of STEC. An animal-host relationship for certain serotypes and a bacteriophage-serotype relationship were observed for both sheep and cattle STEC. This study will focus on health risk posed by thes e ruminant STEC. The knowledge of the occurrence of STEC in the Norwegian population is scarce. The question whether STEC has been established in humans as part of the normal intestinal microbial flora or whether the human STEC has been transmitted from the ruminant reser voir, will be adressed. The specificity of the stx bacteriophage population to infect ruminant and human E. coli will be investigated. The information of STEC/stx-phage epidemiology and transmittance obtained during the study will provide the basis for ri sk assessment, which is of interest for the authorities designing control strategies.