Rectal carriage of enterohemorrhagic Escherichia coli O157 in slaughtered cattle.
Escherichia coli O157:H7 is an important cause of diarrhea, hemorrhagic colitis, and potentially fatal human illness. Cattle are considered a primary reservoir of infection, and recent experimental evidence has indicated that the terminal rectum is the principal site of bacterial carriage. To test this finding in naturally colonized animals, intact rectum samples from 267 cattle in 24 separate lots were obtained immediately after slaughter, and fecal material and mucosal surfaces were cultured for E. coli O157 by direct and enrichment methods. Two locations, 1 and 15 cm proximal to the recto-anal junction, were tested. In total, 35 animals were positive for E. coli O157 at at least one of the sites and 232 animals were negative as determined by all tests. The frequency of isolation and the numbers of E. coli O157 cells were higher at the site closer to the recto-anal junction, confirming our previous experimental findings. We defined low- and high-level carriers as animals with E. coli O157 levels of <1 x 10(3) CFU g(-1) or <1 x 10(3) CFU ml(-1) and animals with E. coli O157 levels of > or =1 x 10(3) CFU g(-1) or > or =1 x 10(3) CFU ml(-1) in feces or tissues, respectively. High-level carriage was detected in 3.7% of the animals (95% confidence interval, 1.8 to 6.8%), and carriage on the mucosal surface of the terminal rectum was associated with high-level fecal excretion. In summary, our results support previous work demonstrating that the mucosal epithelium in the bovine terminal rectum is an important site for E. coli O157 carriage in cattle. The data also support the hypothesis that high-level fecal shedding (> or =1 x 10(3) CFU g of feces(-1)) of enterohemorrhagic E. coli O157 results from colonization of this site.
Low
J Christopher
JC
Animal Health Group, Scottish Agricultural College, UK. chris.low@sac.ac.uk
McKendrick
Iain J
IJ
McKechnie
Caroline
C
Fenlon
David
D
Naylor
Stuart W
SW
Currie
Carol
C
Smith
David G E
DG
Allison
Lesley
L
Gally
David L
DL
D000003:Abattoirs; D000818:Animals; D002353:Carrier State / Q000382:microbiology / Q000662:veterinary*; D002417:Cattle; D002418:Cattle Diseases / Q000382:microbiology*; D015169:Colony Count, Microbial; D004927:Escherichia coli Infections / Q000382:microbiology / Q000662:veterinary; D019453:Escherichia coli O157 / Q000302:isolation & purification*; D012007:Rectum / Q000382:microbiology*