Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: April 15, 2008
Publication Date: June 18, 2008
Citation: Callaway, T.R., Edrington, T.S., Krueger, N.A., Anderson, R.C., Bauer, N., Nisbet, D.J. 2008. Effects of dried distillers grain on E. coli O157:H7 and Salmonella in pure culture and in mixed ruminal and fecal microorganism fermentation in vitro [abstract]. Abstracts of 6th INRA-RRI Gut Micribiome Symposium, June 18-20, 2008, Clermont-Ferrand, France. p. 92. Technical Abstract: During the past 5 years, the amount of corn processed to ethanol has more than doubled in the United States, with an additional doubling in ethanol production via corn fermentation expected by 2010. Distillers grain (DG) is a by-product from ethanol fermentation that is fed to cattle because of its high energy and protein content and low cost; as ethanol production has increased, so has consumption by cattle of DG. Ruminant diets have been shown to have a potent impact on the intestinal population and fecal shedding of foodborne pathogens such as E. coli O157:H7 and Salmonella. Feedstuffs such as barley have been shown to increase fecal shedding of E. coli O157:H7 in many studies, and recent research has shown that dried distillers grain (DDG) can increase shedding of E. coli O157:H7 in cattle. This study was designed to determine if the increase in shedding was due to a direct effect on the pathogens or mediated indirectly through the mixed microbial population of the gut. In the present study, we added ratios of corn meal and DG (up to 1% w/v) to pure culture incubations (n = 3) of E. coli O157:H7 strain 933 and 6058 and Salmonella Typhimurium and Newport. Populations of EC 6058 and S Newport increased by almost 1 log**10 CFU/ml, however, a similar result was obtained from pure corn meal. When these pathogens were incubated with rations of corn meal and DG in mixed ruminal fluid fermentations (n = 4) of S. Typhimurium and Newport, the populations were increased approximately 0.1-0.5 log**10 CFU/ml, respectively, and EC 933 populations were increased approximately 0.6 log**10, while EC 6058 populations decreased 0.3 log**10. When the fermentations (n = 4) contained mixed fecal fluid, DG increased EC 933 and 6058 populations increased approximately 0.2 log**10, while DG increased SN populations 0.8 log**10 and ST populations were unchanged. Results indicate that the inclusion of distillers grain does not directly affect E. coli O157:H7 or Salmonella growth in pure culture. In our study, DG caused no significant changes (P greater than 0.1) in pathogen populations in mixed ruminal and fecal fermentations, therefore, the reported effects of DG on E. coli O157:H7 shedding appear to not be due to an alteration in the population of the rumen or colon that provides a selective advantage to these pathogens.