Submitted to: American Society for Microbiology Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 3/2/2004
Publication Date: 5/23/2004
Citation: Wells, J.E., Berry, E.D., Miller, D.N., Varel, V.H. 2004. Effect of plant phenolics on Escherichia coli O157:H7 survival in bovine feces. In: Proceedings of the 104th General Meeting of the American Society for Microbiology, May 23-27, 2004, New Orleans, Louisiana. 2004 CDROM.
Technical Abstract: Numerous reports have shown the potential effect of a hay diet to decrease the Escherichia coli O157:H7 shedding in feedlot cattle feces, but a mechanism has not been determined. The survival of E. coli O157:H7 in feces composited from animals fed a bromegrass hay diet was examined using a streptomycin-resistant laboratory strain (E. coli O157:H7 43895) as a marker added to the feces and enumerated by dilution and plating onto SMAC-streptomycin agar plates. Initially (animals on diet < 1 month), E. coli O157:H7 viable cells decreased rapidly in the feces and no viable cells were observed after 30 days. However, in samples collected from animals that had been consuming the hay diet for more than one month and were well adapted to the diet, E. coli O157:H7 cells did not decrease as rapidly and viable cells were observed for 120 days. Plant phenolics are known antimicrobial agents, are found in bromegrass hay (up to 1% of the dry matter), and are metabolized in the rumen of adapted animals. In subsequent studies, feces were collected from silage-fed and corn-fed animals and treated with the plant phenolic (trans-cinnamic acid, p-coumaric acid or ferulic acid) at 0.0, 0.1 and 0.5% levels. When 0.5% trans-cinnamic or 0.5% p-coumaric was added to feces from silage-fed animals, the E. coli O157:H7 death rate increased significantly (17-fold and 23-fold, respectively) compared to no addition. In feces from corn-fed animals, E. coli O157:H7 death rates were significantly faster for 0.1% and 0.5% trans-cinnamic acid (7- and 13-fold), 0.1% and 0.5% p-coumaric acid (3- and 8-fold), and 0.5% ferulic acid (3-fold). In examination of the pooled data, the fecal sample pH (range of 5.3 to 6.3) had a slight effect on the death rate of E. coli O157:H7, but a lower fecal pH did significantly enhance the effects of phenolic acids to kill E. coli O157:H7. These data suggest that plant phenolic acids common to forages and hays can decrease viable cells of fecal E. coli O157:H7.