Distribution and virulence of Escherichia coli in the small intestines of calves with and without diarrhea
Isaacson, R.E.; Moon, H.W.; Schneider, R.A.
American Journal of Veterinary Research 39(11): 1750-1755
1978
ISSN/ISBN: 0002-9645 PMID: 367232 Document Number: 137012
Calves, 1-17 days old, were obtained from cattle herds affected with calf diarrheal disease. Of 62 calves, 34 had diarrhea. Of 32 (2 died before sampling) calves with diarrhea, 9 had > 108 enterotoxigenic E. coli (ETEC)/5 cm of ileum and were considered to have ETEC-induced diarrhea. The ETEC also were isolated from 5 other diarrheal and 6 nondiarrheal calves. Of the E. coli isolates from calves with diarrhea, 53% as well as 15% of the E. coli isolates from calves without diarrhea were enterotoxigenic. More E. coli were in the ilea of calves with ETEC-induced diarrhea than were in the ilea of calves with diarrhea induced by agents other than ETEC; the number of E. coli in the ilea of calves from both diarrheal groups was significantly (P .ltoreq. 0.05) higher than in calves without diarrhea. In calves with ETEC-induced diarrhea, significantly (P .ltoreq. 0.0001) more E. coli were in the ileum than in the jejunum. Samples of feces obtained from some calves contained heat-stable enterotoxin (ST); observation of ST in feces did not always correspond to that in calves that were infected with ETEC. Fecal samples from some calves with ETEC-induced diarrhea did not contain ST, although fecal samples from some calves not infected with ETEC apparently did contain ST. The existing procedures to detect K99 pili on E. coli were modified by using trypticase soy broth for the passage medium instead of liquid Minca and by incubating broth cultures with vigorous shaking. Using this procedure, K99 was detected on 87.5% of the ETEC and on none of the non-ETEC. Five K99-negative ETEC isolates had 987 pili; these strains apparently were not causing diarrhea. Immunofluorescent staining of ileal sections, using K99-specific antiserum, resulted in the observation of fluorescing bacterial layers on the villi from 9 of 9 calves with ETEC-induced diarrhea. None of the ileal sections taken from the 51 other calves stained with the K99-specific immunofluorescent stain.