Survival of Escherichia coli O157:H7 in feces from corn- and barley-fed steers

The survival of Escherichia coli O157:H7 in feces from steers fed corn (CO) or barley (BA) was evaluated at −10, +4 and +22 °C. Fecal pats were inoculated with a four-strain mixture of nalidixic-acid resistant E. coli O157:H7 at two levels: 10 3 CFU g −1 (low, L) and 10 5 CFU g −1 (high, H). At −10 °C, duration of survival of E. coli O157:H7 was reduced ( p < 0.05) in CO-L (35 days) compared to BA-L (49 days), likely due to the effects of fecal volatile fatty acids in combination with a fecal pH of 0.05) observed in the duration of survival or rate of decline of E. coli O157:H7 among treatments. Survival of E. coli O157:H7 was twice as likely ( p < 0.05) at 22 °C than at 4 °C and −10 °C. While pH and dry matter content increased, and volatile fatty acid concentrations decreased over 84 days at all three temperatures, these changes were most pronounced at 22 °C. Survival of E. coli O157:H7 for extended periods of time in feces from both corn- and barley-fed animals was demonstrated, thus fecal material may serve as a vector for the transmission of the organism. The greater survival of E. coli O157:H7 at 22 °C suggests that temperature may play a role in the seasonality of transmission and prevalence of this bacterium in feedlot cattle. The reported greater prevalence of E. coli O157:H7 in cattle fed barley as compared to those fed corn does not appear to be related to elevated risk of transmission arising from differential survival of the bacterium in feces.