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 degrees 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 degrees 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 < 6.5. At 4 degrees C, E coli O157:H7 was detected in BA-H, CO-H, CO-L and BA-L for 77, 77, 56 and 63 days, respectively, with no difference (p > 0.05) observed in the duration of survival or rate of decline of E coli 01 57:H7 among treatments. Survival of E. coli O157:H7 was twice as likely (p < 0.05) at 22 degrees C than at 4 degrees C and -10 degrees 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 degrees 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 O157:147 at 22 degrees 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. (c) 2005 Federation of European Microbiological Societies. Published by Elsevier B.V. All rights reserved.