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1. Compare the prevalence of Salmonella hide contamination on cull dairy cattle, cull beef
cattle and fed cattle.<P>
2. Determine whether the PNW differs from the Eastern/Central/Southern regions of the
US in the frequency of hide contamination with Salmonella by comparing WSU results
with those of America's Beef Producers funded collaborators in Nebraska and Texas.<P>
3. Compare the prevalence of hide contamination with Salmonella before and after preslaughter washes with hyper-chlorinated water. <P>
4. Identify disseminated resistance plasmids among MDR Salmonella isolated from cull and
fed cattle.
Findings: Reports of Salmonella food poisoning originating from beef are uncommon, but the frequent occurrence of Salmonella contamination in the environment and on the hides of cattle is a potential risk, since dust from hides may contaminate carcass surfaces. In addition, some of these Salmonellas are resistant to multiple antibiotics, which may increase the difficulty of treatment should human infection result. This project resulted in four main findings: 1: hide contamination with Salmonella was relatively uncommon in the Pacific Northwest packing plants compared to other regions; 2) hide contamination with Salmonella was seasonal and was more common on culled (older) dairy and beef breed cattle than on feedlot fed (younger) cattle; 3) washing cattle prior to slaughter with chlorinated water did not reduce Salmonella contamination; and 4) while the Salmonella isolated from cull cattle in the Pacific Northwest were largely similar to those isolated from sick animals and from ill humans in this region, the resistant Salmonella isolated from cull cattle in the West carried their resistances differently. This different carriage may provide a marker for human infection of these strain types. The most intriguing finding of this study is the lower frequency of Salmonella contamination in the Pacific Northwest study site compared to other regions. Further research to understand the basis for this difference could lead to new approaches to reducing the potential of Salmonella contamination on beef products.