Public health risk of the ubiquitous reservoir of Shiga toxin-encoding Escherichia coli in animals

Shiga toxin-producing Escherichia coli (STEC), including E. coli serotype O157, are important foodborne pathogens worldwide. The Shiga toxin protein (Stx) contributes to the pathogenesis of STEC-mediated gastroenteritis and is the primary factor responsib le for Hemolytic Uremic Syndrome (HUS), a life-threatening systemic complication of enteric STEC infection. The Shiga toxin-encoding genes (stx) are located on lysogenic double-stranded DNA phages that form a heterogeneous family of stx converting phages. Dissemination of Stx-encoding phages by transduction is the most likely mechanism for emergence of new STEC serotypes and the intergenic spread of stx genes. In this project we will study STEC from animal- and human sources and the role of Stx-encoding b acteriophages in proportion to pathogenicity of STEC. We will enhance the understanding of factors that underlie carriage, expression and transmission of Stx-encoding phages by comparative genomics and transduction studies. The background for this applica tion is an idea that the pathogenic potential of an STEC is partly a result of a complex interplay between Stx-encoding phages and the host bacterium. The primary object is to study the public health risk of the ubiquitous reservoir of Shiga toxin-encodin g E. coli in animals. The expected results of this project may contribute to the understanding of the public health risk constituted by the documented ubiquitous reservoir of STEC in the food-producing animal reservoir. Such understanding is fundamental f or the development of research-based legalisation controlling food production, which is an expressed goal for the FOOD program of The Research Council of Norway. We will contribute to increased understanding of pathogenicity of STEC and the public health risk associated by this group of bacteria, and then we may be able to provide the food industry, and the society in general, with advice on safer food production.