Examination of Potential Predictors of Salmonella Enterica Contamination in Cattle Feedlot Environments

Bovine peripheral lymph nodes (LNs) have been identified as a potential source of human exposure to Salmonella enterica, when adipose trim containing contaminated LNs is incorporated into ground beef. Results of recent studies suggest that excessively high levels of Salmonella in cattle environments and on cattle hides provide the opportunity for Salmonella to gain entry to bovine peripheral LNs via transdermal abrasions such as insect bites and wounds.
Once located within the bovine lymphatic system, many Salmonella have the ability to persist or even thrive, without obvious negative impact on cattle health and performance. Furthermore, at harvest Salmonella located within bovine tissues are protected from current carcass antimicrobial interventions. Thus pre-harvest interventions will likely be needed to circumvent this point of entry for Salmonella into the human food chain. In order to evaluate the efficacy of pre-harvest interventions it will be necessary to identify reliable methods for monitoring Salmonella prevalence and levels in feedlot environments. Thus, the objective of the research described here was to determine if a reliable "predictor" or "environmental marker" could be identified, that could be used to determine Salmonella prevalence in a given feedlot setting and then further, for a given cohort of cattle, to examine the possible correlation between the level of environmental Salmonella contamination, Salmonella fecal shedding status, and the prevalence of Salmonella in
peripheral lymph nodes of cattle at harvest.
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Objectives: <br/>
1) Identify a "predictor" or "environmental marker" that can be used to determine Salmonella prevalence in feedlot environments and examine the efficacy for the predicting Salmonella prevalence in peripheral lymph nodes. <br/>
2) For a given cohort of cattle, to examine the correlation between environmental Salmonella contamination, Salmonella fecal shedding status, and prevalence of Salmonella in peripheral lymph nodes. </p>