Brown C A, Harmon B G, Zhao T, Doyle M P
Athens Diagnostic Laboratory, University of Georgia, Athens 30602, USA.
Appl Environ Microbiol. 1997 Jan;63(1):27-32. doi: 10.1128/aem.63.1.27-32.1997.
Nine weaned calves (6 to 8 weeks of age) were given 10(10) 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 faces 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 rumen 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.
通过口服胃插管法给9头断奶犊牛（6至8周龄）接种10(10) CFU由5种菌株组成的肠出血性大肠杆菌O157:H7混合菌液。3头犊牛最初出现短暂发热，5头犊牛出现短暂轻度腹泻，之后在为期13至27天的研究中，犊牛临床症状正常。接种后前2周，所有犊牛粪便中肠出血性大肠杆菌O157:H7数量急剧下降。此后，所有犊牛体内均持续存在少量肠出血性大肠杆菌O157:H7，在粪便和瘤胃内容物中可间歇性检测到。虽然禁食使4头之前粪便中肠出血性大肠杆菌O157:H7数量较少的犊牛粪便中该菌的排出量增加了1至2个对数10/g，但禁食对粪便中肠出血性大肠杆菌O157:H7排出量的影响在该菌数量较多的犊牛中各不相同。剖检时，在消化道以外的部位未分离出肠出血性大肠杆菌O157:H7。剖检时，所有犊牛的前胃或结肠中均分离出肠出血性大肠杆菌O157:H7。胃肠道内容物中的肠出血性大肠杆菌O157:H7数量多于相应的黏膜切片中的数量，且没有组织学或免疫组化证据表明肠出血性大肠杆菌O157:H7黏附于黏膜。总之，在这些实验条件下，肠出血性大肠杆菌O157:H7对断奶犊牛无致病性，虽然它似乎不会长时间定植于黏膜表面，但肠出血性大肠杆菌O157:H7在瘤胃和结肠内容物中持续存在，作为粪便排出的来源。
