title: Heat-stable (STa) enterotoxin of enterotoxigenic Escherichia coli: binding of the enterotoxin to coagulated milk and casein.
abstract: 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.
mesh_terms: 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
chemical_list: D001427:Bacterial Toxins; D002364:Caseins; D004768:Enterotoxins; D029968:Escherichia coli Proteins; C034151:heat stable toxin (E coli)