Impact of the Probiotic Organism Megasphaera elsdenii on Escherichia coli O157:H7 Prevalence in Finishing Cattle

Feedlot cattle commonly shed the foodborne pathogen Escherichia coli O157:H7 in their feces. Megasphaera elsdenii (ME), a lactic acid-utilizing bacterium, is commonly administered to cattle to avoid lactate accumulation in the rumen and to control ruminal acidosis. The impact of administering ME on foodborne pathogen prevalence, specifically E. coli O157:H7, has not been explored. The purpose of this study was to quantify E. coli O157:H7 prevalence in finishing cattle administered ME. Cattle (n = 448) were assigned to treatments in a randomized complete block design with repeated measurements over two sampling periods. Treatments were arranged as a 2 × 2 factorial containing: ruminally protected lysine (RPL; included for a complementary study) fed at 0% or 0.45% of diet dry matter; with or without ME. Freeze-dried ME was administered as an oral drench (1 × 1010 CFU/steer on day one) and then top dressed onto basal diets (1 × 107 CFU/steer) daily thereafter. Rectoanal mucosal swabs (RAMS) were obtained from animals before harvest to determine the E. coli O157:H7 prevalence. The inclusion of RPL (P = 0.2136) and ME (P = 0.5012) did not impact E. coli O157:H7 prevalence, and RPL was not included in any significant interactions (P > 0.05). A significant interaction was observed between ME and sampling period (P = 0.0323), indicating that the effect of ME on E. coli O157:H7 prevalence varied over the sampling period. A diet containing ME reduced the odds of E. coli O157:H7 prevalence by 50% during sampling period 1 (8.0% and 14.7% for cattle with and without ME, respectively) and increased the odds by 23% during sampling period 2 (10.8% and 8.9% for cattle with and without ME, respectively). Administering ME in cattle diets did not impact E. coli O157:H7 in feedlot cattle. This is the first study to investigate the use of ME as a preharvest food safety intervention in cattle, and additional research is necessary to determine the efficac