Submitted to: Foodborne Pathogens and Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/15/2015
Publication Date: 4/1/2016
Publication URL: http://handle.nal.usda.gov/10113/62565
Citation: Luedtke, B.E., Bosilevac, J.M., Harhay, D.M., Arthur, T.M. 2016. Effect of direct-fed microbial dosage on the fecal concentrations of enterohemorrhagic Escherichia coli in feedlot cattle. Foodborne Pathogens and Disease. 13(4):190-195. doi:10.1089/fpd.2015.2063
Interpretive Summary: Food safety is a continual concern during the processing of beef from farm to fork. Different types of E. coli can vary from causing severe disease to not harming humans. Some feedlots feed a ration of probiotics (beneficial bacteria) that have been reported to reduce levels of some pathogenic E. coli. However, data on the effectiveness of probiotics for reducing all pathogenic E. coli is lacking and some reports on the reduction of specific E. coli using probiotics are contradictory. To address these issues, we compared the total pathogenic E. coli load in feces from cattle that were fed a commercial probiotic at two different levels. An experimental DNA-based assay designed to detect presence and levels of all types of pathogenic E. coli directly from the feces, even at low levels was used. This assay did not find a difference in the total pathogenic E. coli load between the two probiotic dose levels. These results provide information to cattle producers on the effectiveness of a probiotic at different doses on the fecal load of pathogenic E. coli and demonstrate the effectiveness of a new DNA-based assay for total pathogenic E. coli.
Technical Abstract: Contamination of beef products by Shiga toxin-producing Escherichia coli (STEC) is a concern for food safety with a particular subset, the enterohemorrhagic E. coli (EHEC), being the most relevant to human disease. To mitigate food safety risks, pre-harvest intervention strategies have been implemented to reduce EHEC in cattle. One class of interventions that has been widely used in feedlots is the direct-fed microbials (DFMs), which can contain various dosing rates of probiotic bacteria. Here we compare the use of two different doses of a commercially available DFM on the total EHEC load. The DFMs used were the standard 106 CFUs/head/day dose of Bovamine® (Nutrition Physiology Company, Guymon, OK) and the higher dose, Bovamine® Defend™ (Nutrition Physiology Company), which is dosed at 109 CFUs/head/day. To analyze the total EHEC fecal concentration, 480 head of cattle were randomly assigned a DFM feed regimen lasting approximately 5 months prior to the recovery of samples using recto-anal mucosal swabs. A qPCR assay targeting ecf1 was used to enumerate the total EHEC fecal concentration for the 240 head fed the low dose DFM and the 240 head fed the high dose DFM. No significant difference (P>0.05) in the fecal concentration of total EHEC was observed between the two doses. This suggests that using an increased dosage provides no reduction in the total EHEC fecal concentration of feedlot cattle.