ISOLATION AND PURIFICATION OF COLICIN ECL-12, A BACTERIOCIN THAT INHIBITS STRAINS OF ESCHERICHIA-COLI O157-H7

A swine fecal isolate, identified as Escherichia coli ECL12, was found to produce an antimicrobial substance designated as colicin ECL12. Co licin ECL12 was inhibitory against 20 strains of E. coli O157:H7 previ ously isolated from both human and bovine feces. Identification of the producer strain was determined phenotypically by biochemical and morp hological tests. Colicin ECL12 was sensitive to several proteolytic en zymes. Adsorption of colicin ECL12 to sensitive cells of E. coli O157: H7 was bactericidal, resulting in a 2 log reduction in viable cell cou nts. Colicin ECL12 was purified from strain ECL12 by cell extraction a nd ion-exchange chromatography. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of colicin ECL12 resolved a single protein with a molecular weight of approximately 65,000.