[Isolation of the thermolabile E. coli enterotoxin and the study of its biological properties].

Enterotoxin was obtained from the culture of E. coli O15 by salt precipitation and gel-chromatography. The toxic activity of the preparation increased during the isolation and purification: 60-fold according to the results of the method of ligated rabbit intestinal segment and 66-100-fold according to the skin test. The "plateau" and the second fraction obtained as a result of gel-chromatography were inactive according to the results of the method of ligated intestinal segment, but possessed PF-activity in the skin test. Two suppositions are put forward: 1) possibly the factor of vascular permeability and the diarrheal factor were two different substances ((molecules), or 2) the skin test was more sensitive for determination of the toxicity than the method of the ligated segment of rabbit intestine.