Location: Meat Safety & Quality ResearchTitle: Determination of gastrointestinal tract colonization sites from feedlot cattle transiently shedding or super-shedding Escherichia coli O157:H7 at harvest
|Wells, James - Jim|
|KIM, M - Chonnam National University|
|Bono, James - Jim|
|Kalchayanand, Norasak - Nor|
|MEANS, W - University Of Wyoming|
Submitted to: Journal of Applied Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/26/2020
Publication Date: N/A
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 two years, feedlot cattle were sampled multiple times for faecal shedding of E. coli O157:H7. Just prior to harvest (1 to 2 days), animals that were super-shedders (>=10*4* CFU g-1 of faeces) were specifically identified, and based on the longer term screening data, pen cohorts that were low-shedders (years 1 & 2) or chronic-shedders (year 1) were also identified. At harvest, samples were collected from the mouth, rumen, abomasum, ileum, caecum, large intestine, rectum, and rectoanal junction (RAJ) for enumeration and enrichment of E. coli O157:H7. Across all animal groups and GIT locations, the mouth samples exhibited the greatest prevalence for the pathogen, and the abomasum and rumen exhibited the lowest prevalences (P < 0.05). However, the percentage of samples with enumerable levels was greatest for the RAJ (P < 0.05). Super-shedders had significantly greater prevalence for all GIT locations except the mouth and abomasum compared to the low- and chronic-shedders. Samples from the super-shedders were enumerable for most GIT locations, but the percentage of samples enumerable from the rectum and RAJ were the only locations that were significantly greater (P < 0.05). Conclusions: Across all animals naturally exposed to E. coli O157:H7, the risk of ingestion of the pathogen is high based on the mouth samples, but the rumen and abomasum exhibited the lowest levels for the pathogen. In the super-shedding animals, E. coli O157:H7 levels rebounded in the ileum. In super-shedders, the primary site of colonization was at the RAJ, but the rectum also was a major location for pathogen colonization. Significance and Impact: The RAJ is the primary site for E. coli O157:H7 colonization in super-shedding cattle, however low-shedding cattle had lower pathogen levels throughout the GIT and identifying intrinsic GIT factors that reduce passage of the pathogen may minimize risk of RAJ colonization in cattle.