Evaluation of the efficacy of three direct fed microbial cocktails to reduce fecal shedding of E. coli O157:H7 in naturally colonized cattle and fecal shedding and peripheral lymph node carriage of Salmonella in cattle

Authors: BROWN, TYSON - Cargill, Incorporated; EDRINGTON, THOMAS - Diamond V Mills, Inc; Genovese, Kenneth - Ken; He, Louis; Anderson, Robin; Nisbet, David

Submitted to: Journal of Food Protection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/12/2019
Publication Date: 12/6/2019
Citation: Brown, T.R., Edrington, T.S., Genovese, K.J., He, L.H., Anderson, R.C., Nisbet, D.J. 2019. Evaluation of the efficacy of three direct fed microbial cocktails to reduce fecal shedding of Escherichia coli O157:H7 in naturally colonized cattle and fecal shedding and peripheral lymph node carriage of Salmonella in experimentally infected cattle. Journal of Food Protection. 83(1):28-36. https://doi.org/10.4315/0362-028X.JFP-19-208.
DOI: https://doi.org/10.4315/0362-028X.JFP-19-208

Interpretive Summary: Cattle can be important carriers of foodborne pathogens that cause serious illness in humans if they consume contaminated and undercooked meat. These pathogens can be carried into the processing plant in the animal’s gastrointestinal tract or attached as fecal material to the animal’s hide. Once inside the processing facility, these pathogens can accidentally come in contact with and ultimately contaminate the beef products meant for human consumption. In some cases, such as with Salmonella, the pathogens can infect the portion of the animal that becomes meat, which makes decontamination at the processing plant very difficult. Accordingly, we tested several potential strategies employing probiotic bacteria that could be fed to the animal to get rid of these pathogens before the animal enters the processing facility. These probiotic (or beneficial) bacteria are designed to improve the microbial balance within the gastrointestinal tract and have been included in animal rations to improve performance and reduce pathogenic bacteria. Results from our animal studies did not achieve significant reductions in carriage or shedding of the pathogens. Thus, under the conditions of our studies, the prebiotic preparations did not work as intended. These results provide farmers and ranchers important information on what products and what application methods are most cost effective in enhancing the microbiological safety of the beef products produced for the American consumer.

Technical Abstract: Two experiments were conducted to evaluate the feeding of direct fed microbials (DFM) on fecal shedding of E. coli O157:H7 in naturally-infected cattle (Exp. I) and on Salmonella in the peripheral lymph nodes (PLN) of experimentally-infected cattle (Exp. II). Thirty head, 10 per treatment, were used in each experiment. Treatments in Exp. I consisted of: Control – lactose carrier only; DFM1 – 1:1 ratio of Enterococcus faecium and Lactobacillis animalis; and DFM2 – 1:1 ratio of Lactobacillus acidophilus and Pediococcus acidilactici, whereas in Experiment II, DFM3 – replaced DFM1; 1:2 ratio of Lactobacillus reuteri and other Lactobacillus strains). Treatments were mixed in water and applied as a top-dress to each pen’s daily ration for 50 days. Approximately halfway through each experiment, the concentration of DFM was doubled for the remainder of the study. Fecal samples were collected throughout Experiment I and cultured for E. coli O157:H7. Cattle in Experiment II were inoculated intradermally with Salmonella Montevideo on days 32, 37, and 42 prior to necropsy on days 49 and 50 (5 head/treatment on each day). Innate immune function was assessed on days 29, 49, and 50. In Experiment I, fecal concentration and prevalence of E. coli O157:H7 were not different (P > 0.10), nor was there an effect (P = 0.95) on the percentage of super-shedders (cattle shedding greater than or equal to 3.0 CFU Log10/g feces). In the second experiment, no treatment differences (P > 0.05) were observed for Salmonella in the PLN. Immune functions, as measured by monocyte nitric oxide production and neutrophil oxidative burst, were decreased (P < 0.05) in the DFM treatments. While results of this research showed little to no effect of feeding these DFMs on E. coli O157:H7 or Salmonella in cattle, increasing the length of administration, similar to that of commercial cattle feeding, could potentially elicit treatment differences.