Roles of Phage-Encoded Functions in Enterohemorrhagic Escherichia coli

Enterohemorrhagic Escherichia coli (EHEC) O157:H7 are emerging foodborne pathogens that have caused large-scale outbreaks of gastrointestinal illness in developed countries during the past two decades. Intestinal infection can lead to diarrhea, hemorrhagic colitis or more severe systemic complications, such as hemolytic uremic syndrome. The production of Shiga toxins by E. coli O157:H7 strains plays an important role in the development of serious complications following EHEC infection. Shiga toxin 2 (Stx2) is associated with the most severe outcomes of infection. The genes for Stx2 in human clinical isolates are encoded on temperate lambdoid bacteriophages. Expression of the toxin genes and release of Stx2 is dependent upon prophage induction and lysis of the bacterial host. We are investigating the contribution of subsequent infection of commensal bacteria in amplification of phage and toxin production. Additional studies underway in the lab are directed towards elucidating factors that may lead to prophage induction during infection and understanding the host range determinants of Shiga toxin phages.