ARS | Publication request: Survival of O157:H7 and non-o157 serogroups of Escherichia coli in bovine rumen fluid and bile salts

Submitted to: Foodborne Pathogens and Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 5, 2012
Publication Date: November 7, 2012
Citation: Free, A.L., Duoss, H.A., Bergeron, L.V., Shields-Menard, S.A., Ward, E., Callaway, T.R., Carroll, J.A., Schmidt, T.B., Donaldson, J.R. 2012. Survival of O157:H7 and non-O157 serogroups of Escherichia coli in bovine rumen fluid and bile salts. Foodborne Pathogens and Disease. 9:1010-1014.

Interpretive Summary: Enterohemorrhagic E. coli (EHEC) such as E. coli O157:H7 present a serious threat to food safety and are commonly found in the gastrointestinal tract of cattle. This study was designed to determine if there were differences in the ability of EHEC to survive exposure to bile salts and ruminal fluid. Ruminal fluid was a good medium for growth of the serotypes tested, but variation in survival followed by exposure to bovine bile salts existed. This suggests that non-O157 EHEC may survive differently in the gut of cattle than O157:H7 isolates.

Technical Abstract: Escherichia coli are gram negative, facultative anaerobic bacteria that colonize within the intestines of animals and humans. Enterohemorragic strains of E. coli (EHEC) pose a serious health risk to humans yet reside asymptomatically within ruminants. In particular, bovine serve as the major reservoir for these bacteria. Research related to EHEC has historically been focused upon O157:H7. However, with an increase in food-borne outbreaks of non-O157 origin and forthcoming changes in test for non-O157:H7 by the USDA, there is now a critical need to understand the biological activity of non-O157 serotypes as well. The focus of this study was to determine whether variations exist in the ability of different serotypes of EHEC to survive within bovine bile salts and rumen fluid. The results of this study indicate that the five serotypes tested (O157:H7, O111:H8, O103:k:H8, O145:H28, and O26:H11) grew well in rumen fluid. Most notably, certain serotypes appeared to have an improved ability to replicate within the rumen fluid when compared to O157:H7. Variations were also observed in the survival of these non-O157 strains in bovine bile salts in comparison to O157:H7. These data suggest that non-O157 serotypes of E. coli may respond differently than O157:H7 to the environment of the bovine intestine. Further work is needed to decipher how these variations correlate with alterations in colonization within ruminants.