Novel Molecular Approaches to Eradicating E. coli O157 From the Bovine GI Tract

Enterohemorrhagic E. coli (EHEC) cause a variety of gastrointestinal infections. EHEC serotype O157: H7 has emerged as an important foodborne pathogen that threatens many aspects of the food industry. A crucial component of O157:H7 pathogenesis and epidemiology is its ability to survive environmental stresses imposed by the infected host. The successful pathogen survives this assault through the induction of microbial stress response systems. The investigators have identified two EHEC stress response systems essential for this organism to survive in the bovine gastrointestinal tract,an important reservoir of O157:H7. This project will test strategies designed to corrupt these stress response systems, thereby rendering O157 unable to survive in the gastrointestinal tract. (Strategy 1) A natural E. coli peptide was found that dramatically inhibits the activity of sS , an important stress response sigma factor required to transcribe numerous stress response genes. The smallest peptide retaining anti-s S activity will be determined and its activity optimized for use as an antimicrobial agent. (Strategy 2) Several O157:H7-specific bacteriophage have been identified and will be used to design an antimicrobial 'phage cocktail' that will be tested for its ability to kill O157 In the calf shedding model. In addition to phage that can kill O157, other phage may be useful as O157 'smart bombs' designed to deliver genes encoding antimicrobial peptides directly to O157. Although this project specifically addresses the problem of O157 in the farm environment, its success will have a broad impact on the design and implementation of antimicrobial therapies for many infectious agents.