In vitro effects of a mixture of Escherichia coli heat-stable enterotoxins (STa and STb) on isolated jejunum of 3-week-old male pigs were studied, using everted intestinal sac techniques. Heat-stable enterotoxins increased chloride secretion and chloride absorption in everted intestinal sacs. The increase of secretory flux was greater than that for absorptive flux. Vasoactive intestinal peptide (6 x 10-9M) increased chloride secretion, but had no effect on chloride absorption. Neither vasoactive intestinal peptide nor pilocarpine (10-5M) had additive effect to ST. Secretory effects of ST were not blocked by atropine 2 x 10-5M), clonidine (10-6M), or morphine (4.2 X 10-6M).

We attempted to determine whether weaning is required for induction of diarrhea in pigs with postweaning enterotoxigenic Escherichia coli infection. Three-week-old newly weaned pigs and their suckling littermates were inoculated with the K88+ enterotoxigenic E coli strain M1823B. Fourteen of 21 weaned and 12 of 20 suckling pigs were genetically resistant to intestinal adhesion by the K88+ strain of E coli; they remained healthy, and gained weight at similar rates. Both groups of K88-resistant pigs gained weight faster, and shed fewer bacteria of strain M1823B in their feces, than did their K88-susceptible counterparts. Diarrhea developed in K88-susceptible pigs in the weaned (6 of 7 pigs) and suckling (4 of 8 pigs) groups, and 1 of the 4 affected suckling pigs died from complications resulting from diarrhea. The incidences of diarrhea, weight gain rates, and the numbers of strain M1823B shed in feces of susceptible weaned and suckling pigs were not significantly (P > 0.05) different. Diarrhea scores of susceptible weaned pigs were significantly (P < 0.02) higher than those of susceptible suckling pigs on the second day after inoculation. In this experimental model, it was concluded that weaning is not required for induction of diarrhea, but may modestly increase its severity.

A reproducible model of postweaning colibacillosis was obtained by controlling management and environmental variables to simulate conditions often seen at weaning. Suckling pigs were exposed briefly to starter diet at 1 week of age, weaned at 3 weeks of age, held at an ambient temperature of 20 +/- 2 C, again given the starter diet. One day after weaning, each pig was given 10(10) colony-forming units of enterotoxigenic Escherichia coli strain M1823B (0157:K88ac:H43-LT+ STb+) in broth containing 1.2% sodium bicarbonate via stomach tube. In vitro adhesion by strain M1823B to isolated intestinal branch borders was used to tst pigs for susceptibility to K88. In this model, 3 syndromes were induced in susceptible pigs: (1) peracute fatal diarrhea; (2) moderate diarrhea, weight loss, and fecal shedding of the inoculum strain; and (3) no diarrhea, weight loss, and fecal shedding of the inoculum strain. Rotavirus particles were not found in fecal specimens of pigs with diarrhea. The K88-susceptible, noninoculated control pigs remained clinically normal. It was concluded that susceptibility to adhesion by K88+ enterotoxigenic Escherichia coli was a requirement for the production of disease in this model; inoculation with rotavirus was not necessary.

This paper deals with the 0 groups of citrate utilizing variants of Escherichia coli (Cit+ E. Coli) isolated from cattle, the production of colicin, hemolysin, K99 antigen, heat stable enterotoxin, and the isolation of plasmid DNA. Among 42 Cit + E. Coli, 12 strains were 020, 9 strains 08, 5 strains 045, 3 strains 0115, 1 strain 064, 1 strain 0139 and remaining strains (11) were untypable. Thirty-nine(81.3%)out of 48 Cit + E. Coli produced colicin and 13(27.0%) produced hemolysin. Of 12 cit + E. coli bearing K99 antigen, 6(50.0%) produced heat stable enterotoxin. In gel electrophoresis for the isolation of plasmid DNA, the number of plasmids varied from 1 to 7 in 10 Cit+ E. Coli. Its molecular weight ranged from 2 to 50 Mdalton, and 50 Mdalton plasmid commonly existed in all strains

This study was conducted to isolate etiological agents from the 103 scouring piglets in Kyongnam area and also carried out antimicrobial drug susceptibility test and epidemiogical survey. The incidence of scouring piglet was most prevalent in 81.6% at the age of 2 to 4 weeks after birth, while the rate was less than 10% at the age of 5 to 6 weeks and under 1 week after birth. When comparing the isolation frequency of each etiological agent, enteropathogenic E. coli was most prevalent in 46.6%, thermophilic Campylobacter in 26.2% and Salmonellae was in 8.7% in that order. In the OK serotyping for 117 isolates of enteropathogenic E. coli, type 0141 : K85(20.5%), 0157:K88ac(14.5%), 0138:K81 and 0149:K91 (13.3%) were encountered most frequently. In the biotyping for 27 isolates of thermophilic Campylobacter, most strains of C. jejuni belonged to type I (50.0%) and II (25.0%), and most strains of C. coli belonged to biotype I (78.9%). In the serotyping for 9 strains of Salmonellae, 3 strains were grouped as D, 2 strains as C and 1 strain each was group B and E. The other 2 strains were untypable. The 117 isolates of enteropathogenic E. coli were resistant more than 90% to erythromycin, penicillin, tetracycline and streptomycin, whereas about 90% of the isolates were sensitive to kanamycin and gentamicin. In the case of Salmonellae, all of the isolates were resistant to penicillin, but about 89% of the isolates were sensitive to gentamicin and colistin. All of C. jejuni and C. coli isolates were resistant to cephalothin, but more than 89% of C. jejuni and C. coli were sensitive to kanamycin and gentamicin