Submitted to: International Symposium and Workshop on Shiga Toxin ... Escherichia coli
Publication Type: Abstract Only
Publication Acceptance Date: June 21, 2006
Publication Date: October 29, 2006
Citation: Keen, J.E., Laegreid, W.W. 2006. Gastro-intestinal tract distribution at necropsy of shiga-toxigenic Escherichia coli O157 in naturally-infected cattle [abstract]. Proceedings of the 6th International Symposium on Shiga Toxin (Verocytotoxin)--Producing Escherichia coli Infections, October 29 - November 1, 2006, Melbourne, Australia. Poster No. P04.1.03. Technical Abstract: Healthy adult cattle with gastro-intestinal tract (GIT) transient luminal presence or mucosal colonization by Shiga-toxigenic E. coli (STEC) O157:H7 are a primary zoonotic reservoir of this human pathogen, especially for meat-borne transmission. The GIT distribution of STEC O157 in various experimental animal and challenge-model systems is well studied but may not accurately reflect natural events. STEC O157 in the GIT of naturally-infected cattle has received little attention beyond its occurrence in the proximal (oral cavity) and especially distal (rectum) segments. Our study motivation was to qualitatively determine viable STEC O157 occurrence along the entire GIT of naturally-infected adult cattle. We hypothesized that this distribution would not be limited to the distal large intestine. Four adult female beef cattle identified as fecal shedding STEC O157 were humanely euthanized within 3 to 7 days. Sections at regular anatomical intervals along the entire GIT length (about 50 total sites) were removed aseptically immediately post-euthanasia. The GIT tissues (10 g) and their adjacent luminal contents (ingesta, 10 g) were cultured for STEC O157 separately and in duplicate (approximately 200 culture attempts per animal) using selective broth enrichment, immuno-magnetic separation, and selective agar plating. Tissues were gently rinsed with sterile phosphate-buffered saline prior to culture to remove adherent ingesta. Suspect isolates were confirmed as STEC O157 by enzyme immunoassay for the O157 and H7 antigens and by PCR for shiga-toxin (stx1 and stx2), intimin (eae), hemolysin (hly), O-antigen (rfbEO157) and flagellar (fliCH7) genes. Inter-animal STEC O157 GIT distribution was highly variable. Animals #1 and #3 were ingesta- and tissue-positive solely in the small intestine. Animal #2 was ingesta- and tissue-positive in the upper GIT, the rumen complex, and the small and large intestines. Animal #4 was culture-negative at all locations. These results suggest that the bovine small intestine may support STEC O157 colonization.