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<p>The stated objectives for this work were to:<br/>
The specific objectives of this project were to 1) determine the rate of occurrence and identify risk factors associated with feedlot cattle shedding of E. coli O157:H7 and 2) determine if super-shedder cattle are the result of being infected with specific strains or the result of ingesting a high dose compared to a low dose of E. coli O157:H7 regardless of bacterial strain.</p>
<p>The presence of Escherichia coli O157:H7 super-shedding cattle in feedlots have the potential to increase the overall number (bio-burden) of E. coli O157:H7 for the entire pen of cattle. Elevated bio-burden of E. coli O157:H7 further increases the likelihood of continued inter-animal transmission and new infections with E. coli O157:H7 within and between pens in the feedlot and subsequent hide contamination prior to slaughter. It is important to develop management strategies to reduce the bio-burden of E. coli O157 in feedlots by clarifying methods associated with the occurrence of super-shedders in feedlot cattle. The key to developing such a management strategy is to (1) clarify the mechanism for why a small percentage of feedlot cattle become super-shedders, (2) determine if the level of ingested dose of E. coli O157:H7 is the driver for super-shedding status, and (3) determine whether virulent strains of E. coli O157:H7 exist that are more likely to result in a super-shedder infection and thereby elevate the bio-burden, or is the phenomena of super-shedder cattle independent of the bacterial strain.</p>