Heat-stable (STa) enterotoxin of enterotoxigenic Escherichia coli: binding of the enterotoxin to coagulated milk and casein.
Oral or intragastric inoculation of the STa enterotoxin of Escherichia coli has been the standard laboratory test for that toxin. We demonstrated that the severity of the secretory response of 2-4-day-old mice to a single dose of the toxin was influenced by weaning of these mice. After oral application of 50-250 fmol of purified, radioiodinated STa toxin (12-13 Ci mmol-1) approximately 55-65% of the administered toxin bound to the stomach contents. Binding of the toxin did not destroy its biological activity. The binding was pH dependent; stomach contents bound 75% of the toxin at pH 2.3 and only 7.4% at pH 10.1. The principle in the stomach contents which bound the toxin was also demonstrated in murine and bovine milk. Further studies with renin-coagulated milk and commercial casein indicated that milk casein bound the toxin. Based on these findings, we speculate that in cases of food-poisoning involving casein-containing foods STa toxin may be present in the absence of cultivable enterotoxigenic E. coli.
D000818:Animals; D000833:Animals, Suckling; D001427:Bacterial Toxins / Q000378:metabolism*; D002364:Caseins / Q000378:metabolism*; D002417:Cattle; D004768:Enterotoxins / Q000378:metabolism*; D029968:Escherichia coli Proteins; D005260:Female; D006863:Hydrogen-Ion Concentration; D051379:Mice; D008892:Milk / Q000378:metabolism*; D011247:Pregnancy; D011897:Random Allocation; D013696:Temperature; D014886:Weaning
D001427:Bacterial Toxins; D002364:Caseins; D004768:Enterotoxins; D029968:Escherichia coli Proteins; C034151:heat stable toxin (E coli)