Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: May 30, 2008
Publication Date: July 6, 2008
Citation: Callaway, T.R., Edrington, T.S., Anderson, R.C., Nisbet, D.J. 2008. Effects of the dicarboxylic acids malate and fumarate on E. coli O157:H7 and Salmonella Typhimurium populations in pure culture and mixed ruminal culture in in vitro fermentations [abstract]. American Society of Animal Science/American Dairy Science Association Joint Annual Meeting, July 7-11, 2008, Indianapolis, Indiana. Journal of Animal Science. 86(Supplement 2):26. Technical Abstract: The dicarboxylic acids malate and fumarate increase ruminal pH, reduce methane production, increase propionate and total VFA production, and reduce lactic acid accumulation in a manner similar to ionophores. The mechanism by which these acids effect the ruminal environment is reported to be through stimulation of the ruminal bacterium Selenomonas ruminantium to utilize lactate to form propionate via the succinate-propionate pathway. Therefore, dicarboxylic acids have been suggested for use as non-antibiotic modifiers of the ruminal fermentation, but their impact on the overall microbial ecology of the rumen and gut remains unknown. Therefore, this study was prepared to determine if the addition of dicarboxylic acids to ruminal fermentations effected populations of the human pathogens, Escherichia coli O157:H7 and Salmonella Typhimurium. Pure cultures of E. coli O157:H7 strain 933 and S. Typhimurium were grown with malate and fumarate added at 0, 1, 5, 10, and 20 mM (v/v; n=3 of each acid concentration) at 39 C for 24 h. Neither dicarboxylic acid inhibited (P greater than 0.1) the growth rate or final populations of E. coli O157:H7 or S. Typhimurium. Ruminal fluid was collected from concentrate fed cows (n=2) and E. coli O157:H7 and S. Typhimurium were added to separate ruminal fermentations. Fumarate and malate were added to these in vitro pathogen fermentations at concentrations of 0, 5, 10, and 20 mM (v/v; n=2 of each acid concentration) and were incubated at 39 C for 24 h. Again, the addition of malate or fumarate did not affect (P greater than 0.1) populations of E. coli O157:H7 or S. Typhimurium. However, final pH was increased (P less than 0.05), the acetate:propionate ratio was decreased (P less than 0.05), and total VFA production was increased (P less than 0.05) by greater than or equal to 10 mM dicarboxylic acid addition. These results confirm that dicarboxylic acids can modify the ruminal fermentation, but they do not directly or indirectly influence populations of E. coli O157:H7 or S. Typhimurium in pure or mixed ruminal fluid fermentations.