Determination of gastrointestinal tract colonization sites from feedlot cattle transiently shedding or super-shedding Escherichia coli O157:H7 at harvest

Authors: Wells, James - Jim; Berry, Elaine; KIM, M - Chonnam National University; Bono, James - Jim; Oliver, William; Kalchayanand, Norasak - Nor; Wang, Rong; Freetly, Harvey; MEANS, W - University Of Wyoming

Submitted to: Journal of Applied Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/26/2020
Publication Date: 10/13/2020
Citation: Wells, J., Berry, E.D., Kim, M., Bono, J.L., Oliver, W.T., Kalchayanand, N., Wang, R., Freetly, H.C., Means, W.J. 2020. Determination of gastrointestinal tract colonization sites from feedlot cattle transiently shedding or super-shedding Escherichia coli O157:H7 at harvest. Journal of Applied Microbiology. 129:1419-1426. https://doi.org/10.1111/jam.14684.
DOI: https://doi.org/10.1111/jam.14684

Interpretive Summary: Beef cattle are reservoirs for the foodborne pathogen Escherichia coli O157:H7, and this pathogen is shed in the feces. The primary colonization site in the gut is widely considered to be the rectum-anal junction, but E. coli O157:H7 has been detected throughout the gut of cattle. The current study compared various locations in the gut of those animals determined to be super-shedding E. coli O157:H7 at high levels and control animals that were low-shedders. E. coli O157:H7 was detected most frequently in the mouth of all animals. However, super-shedder animals had higher levels throughout most of the gut locations and had the highest levels of the pathogen in the colon and at the rectum-anal junction. These results suggest that low-shedding animals might have factors that reduce E. coli O157:H7 that could be used to reduce risks from this pathogen.

Technical Abstract: Aims: The objective of the study was to determine levels of Escherichia coli O157:H7 colonization in the gastrointestinal tract (GIT) of cattle naturally-infected shedding the pathogen at low- or super-shedder levels. Methods and Results: Over 2 years, feedlot cattle were sampled multiple times for faecal shedding of E. coli O157:H7. Just prior to harvest (1 - 2 days), animals that were super-shedders (>=10*4* CFU per gram of faeces) were specifically identified, and based on the longer term screening data, pen cohorts that were low-shedders (years 1 and 2) or chronic-shedders (year 1) were also identified. At harvest, samples were collected from throughout the GIT, including the rectoanal junction (RAJ) for enumeration and enrichment of E. coli O157:H7. The mouth samples exhibited the greatest prevalence for the pathogen, and the abomasum and rumen exhibited the lowest prevalences (P < 0.05). Super-shedders had significantly greater prevalence for all GIT locations except the mouth and abomasum compared to the low-shedders, but the super-shedders were the only animals with positive abomasum samples. Samples from the super-shedders were enumerable for most GIT locations, and the rectum and RAJ locations were the only locations that were significantly greater than other locations (P < 0.05). Conclusions: Across all animals naturally exposed to E. coli O157:H7, the risk of ingestion is high, but rumen and abomasum are potential barriers to passage. In super-shedders, the passage through the GIT was greater, allowing colonization in the rectum and at the RAJ. Significance and Impact of the Study: Escherichia coli O157:H7 low-shedding cattle had lower pathogen levels throughout the GIT, indicating intrinsic GIT factors to these cattle may reduce pathogen passage through the GIT, including the abomasum, and minimize risk of RAJ colonization.