Miniats O P, Gyles C L
Can J Comp Med. 1972 Apr;36(2):150-9.
The significance of enterotoxin production and proliferative ability of Escherichia coli in the intestinal tract as related to porcine enteric colibacillosis was studied in 68 gnotobiotic pigs. The animals were monocontaminated at seven to ten days of age with eight selected strains of E. coli. The strains were two naturally occurring porcine enteropathogens - P155 (0149:K91;K88a,c:H10) and P307 (08:K87;K88a,b:H19), two nonenteropathogenic strains - P104 (0139:K82:H1) and F11 (018-ab:K?:H14), and four enterotoxigenic derivatives of the above strains - P104(P155), P104(P307), F11(P155) and F11(P307). The response of the animals was evaluated on the basis of clinical observations and necropsy lesions 22 hours after exposure to the organisms. E.coli counts were determined at seven different levels of the intestinal tract. Cell free extracts of the intestinal contents were examined for enterotoxic activity by the ligated pig intestine loop test. All of the strains possessing the enterotoxin plasmid produced enterotoxin in the pig's intestine and were capable of causing diarrhea. The nonenteropathogenic E. coli failed to do so. The strains possessing the P155 enterotoxin plasmid were more virulent than the corresponding derivatives with the P307 enterotoxin plasmid. Strains P155, P307 and P104(P155) proliferated in the upper small intestine at a greater rate and were more virulent than the other strains. The numbers attained in the upper small intestine by the other enterotoxigenic derivatives were comparable to those of their nonenteropathogenic parent strains. It was considered that enterotoxin produced by E. coli was the essential factor for causing a diarrheic response in gnotobiotic pigs. The virulence of each of the tested strains appeared to be governed by the degree of enterotoxicity associated with a particular enterotoxin plasmid, the numbers attained by these organisms in the upper small intestine, (but not in the lower small intestine or in the colon), and by other undetermined factors.
在68头无菌猪中研究了大肠杆菌在肠道内产生肠毒素的能力和增殖能力与猪肠道大肠杆菌病的关系。这些动物在7至10日龄时用8株选定的大肠杆菌进行单菌感染。这些菌株包括两株天然存在的猪肠道病原菌——P155（0149:K91;K88a,c:H10）和P307（08:K87;K88a,b:H19），两株非肠道病原菌——P104（0139:K82:H1）和F11（018-ab:K?:H14），以及上述菌株的四种产肠毒素衍生物——P104(P155)、P104(P307)、F11(P155)和F11(P307)。在接触这些微生物22小时后，根据临床观察和尸检病变对动物的反应进行评估。在肠道的七个不同部位测定大肠杆菌数量。通过结扎猪肠袢试验检测肠道内容物的无细胞提取物的肠毒素活性。所有携带肠毒素质粒的菌株在猪肠道内产生肠毒素并能够引起腹泻。非肠道致病性大肠杆菌则不能。携带P155肠毒素质粒的菌株比携带P307肠毒素质粒的相应衍生物毒性更强。菌株P155、P307和P104(P155)在上段小肠中增殖速度更快，且比其他菌株毒性更强。其他产肠毒素衍生物在上段小肠中达到的数量与其非肠道致病性亲本菌株相当。据认为，大肠杆菌产生的肠毒素是导致无菌猪出现腹泻反应的关键因素。每种受试菌株的毒力似乎受与特定肠毒素质粒相关的肠毒性程度、这些微生物在上段小肠（而非下段小肠或结肠）中达到的数量以及其他未确定因素的影响。
