Escherichia coli enterotoxin. Purification and partial characterization.

Enterotoxin, a diarrheagenic protein elaborated by pathogenic Escherichia coli strains has been isolated from the supernatant of fermenter cultures of E. coli strain P263, a porcine enteropathogen. Purification steps involving Bio-Gel agarose A-5m, Sephadex G-75 chromatography, and preparative isotachophoresis were used in the isolation. The resulting product appears to be pure according to immunoelectrophoretic, disc electrophoretic, ultracentrifugal, and immunologic criteria. The entertoxin has an apparent molecular weight of 102,000 as judged by gel filtration and sodium dodecyl sulfate polyacrylamide gel electrophoresis, and its isoelectric point is 6.90. The isolated product is highly active in inducing experimental diarrhea in adult rabbits and piglets. It also elicits, in small dosage, a marked increase in adenylate cyclase activity in broken cell preparations of cat heart tissue. The enterotoxin activity is acid-labile and is destroyed by heating at 65 degrees for 30 min. It is suggested that the heat-stable enterotoxin material is derived from heat-labile enterotoxin by forming a complex with endotoxin or capsular material present in the culture supernatant.