Freeze-thaw lysates prepared from strains of Escherichia coli belonging to serogroups O138, O139, and O141 contained a principle (edema disease principle) which induced edema disease in swine. All freeze-thaw lysates contained endotoxic activity that tended to obscure the edema disease syndrome and methods were developed to reduce such activity. Freeze-thaw lysates prepared from E. coli O139 induced the most characteristic edema disease syndrome. Partially purified edema disease principle prepared from O139 freeze-thaw lysates by sequential precipitation with ammonium sulphate and streptomycin sulphate had increased specific activity with markedly reduced endotoxic activity. This material was insoluble at acidic pH but readily soluble at alkaline pH. The effective molecular weight of edema disease principle, based on retention and filtration properties of diaflo membranes, appeared to be greater than 50,000 and less than 100,000. The biological activity of edema disease principle was thermolabile. Sodium deoxycholate treatment of edema disease principle further reduced endotoxic activity. A thermolabile, ammonium sulphate precipitable material was prepared from E. coli O139 that induced a predictable syndrome which resembled edema disease clinically and pathologically following intravenous inoculation in pigs
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