• 1 January 1979
    • journal article
    • research article
    • Vol. 43 (4), 371-379
Abstract
The response of different test systems to preparations of heat-stable enterotoxin (ST) derived from E. coli strains recovered from diarrheal disease of humans, pigs and calves was evaluated. Sterile broth culture supernatants of enterotoxigenic E. coli strains were heated at 65.degree. C for 30 min and tested for presence of ST. Three test systems, (ligated intestine of weaned pigs, ligated intestine of rabbits and the infant mouse test) were used in attempts to detect ST in the culture supernatants. Two patterns of reaction were observed in response to ST-containing preparations: the preparation elicited a response in the 3 tests or the preparation elicited a reaction only in the ligated pig intestine. A response in all 3 tests was observed for 5/5 human ST-producing E. coli, 5/5 bovine enterotoxigenic E. coli, 5/5 atypical porcine enterotoxigenic E. coli, 3/3 ST+LT- porcine E. coli of serogroup 0138:K81 and 4/24 LT+ST+ porcine E. coli. A response only in the ligated pig intestine was obtained with 5/5 ST+LT- porcine E. coli belonging to serogroups other than 0138:K81 and to 20/24 ST+LT+ E. coli from pigs. There may be 2 kinds of ST, 1 of which (ST1) may react in all 3 tests and the other (ST2) which may react only in the ligated pig intestine. The findings underscore the limitations of the infant mouse test as a means of detecting ST in porcine isolates of E. coli, since the test fails to detect ST produced by a large number of these E. coli strains. There appeared to be a relationship between ST kind(s) produced and the animal species from which the producing organism was recovered.