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1. To identify cattle persistently shedding E. coli O157:H7.
<P> 2. To identify physiological and microbiological differences in the intestinal tract between
persistently shedding cattle and controls (non-persistently shedding cattle).
<P>3. To identify sites, areas or locations at which pre-harvest food safety interventions
should be targeted to preclude persistent shedding in finishing cattle.
Findings: A longitudinal study, conducted by scientists at Colorado State University for the Cattlemen�s Beef Board and state beef councils by the National Cattlemen�s Beef Association and funded beef producers and veal producers and importers through their $1-per-head checkoff, has found that within a population of healthy feedlot cattle, there were a small percentage of animals persistently colonized with Escherichia coli O157:H7. The animals identified as persistent shedders did not exhibit any physiological ante-mortem symptoms or any post-mortem histopathology gastrointestinal tissue differences when compared to animals that never shed E. coli O157:H7. Molecular characterization of E. coli O157:H7 isolates demonstrated that a closely related group of E. coli O157:H7 molecular subtypes colonized the gastrointestinal tract of persistent shedders. Molecular subtypes commonly isolated from persistently colonized cattle displayed an increased ability to attach to intestinal epithelial cells than E. coli O157:H7 isolates less commonly found in the sample population. The underlying factors associated with persistent colonization of healthy cattle by E. coli O157:H7 are likely multi-factorial and remain to be fully elucidated.