Experimental Escherichia coli O157:H7 carriage in calves

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Abstract

Nine weaned calves (6 to 8 weeks of age) were given 1010 CFU of a five-strain mixture of enterohemorrhagic Escherichia coli O157:H7 by oral- gastric intubation. After an initial brief period of pyrexia in three calves and transient mild diarrhea in five calves, calves were clinically normal throughout the 13- to 27-day study. The population of E. coli O157:H7 in the feces decreased dramatically in all calves during the first 2 weeks after inoculation. Thereafter, small populations of E. coli O157:H7 persisted in all calves, where they were detected intermittently in the feces and tureen contents. While withholding food increased fecal shedding of E. coli O157:H7 by 1 to 2 log10/g in three of four calves previously shedding small populations of E. coli O157:H7, the effect of fasting on fecal shedding of E. coli O157:H7 was variable in calves shedding larger populations. At necropsy, E. coli O157:H7 was not isolated from sites outside the alimentary tract. E. coli O157:H7 was isolated from the forestomach or colon of all calves at necropsy. Greater numbers of E. coli O157:H7 were present in the gastrointestinal contents than in the corresponding mucosal sections, and there was no histologic or immunohistochemical evidence of E. coli O157:H7 adhering to the mucosa. In conclusion, under these experimental conditions, E. coli O157:H7 is not pathogenic in weaned calves, and while it does not appear to colonize mucosal surfaces for extended periods, E. coli O157:H7 persists in the contents of the rumen and colon as a source for fecal shedding.

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Brown, C. A., Harmon, B. G., Zhao, T., & Doyle, M. P. (1997). Experimental Escherichia coli O157:H7 carriage in calves. Applied and Environmental Microbiology, 63(1), 27–32. https://doi.org/10.1128/aem.63.1.27-32.1997

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