PURIFICATION AND CHARACTERIZATION OF A CYTOTOXIN FROM ENTEROBACTER-CLOACAE

Leukotoxic activity was assayed in clinical isolates of Enterobacter c loacae. Two strains were selected out of 38 by their greater hemolytic activity in blood agar plates. Leukotoxin was purified by salt precip itation, dialysis, chromatography by gel filtration, and high pressure liquid chromatography (HPLC). Human leukocytes, when incubated with p urified E. cloacae toxin, showed high percentages of death and lysis, with time and dose dependence. The chromatographic profile of gel filt ration presented three protein peaks and toxic activity was detected i n the second peak. After HPLC, leukotoxin coeluted with the hemolytic activity and both activities were detected only after 2-mercaptoethano l treatment. Coomassie-stained sodium dodecyl sulfate - polyarylamide gels showed a single band. This band was estimated to represent a prot ein of 13 300 Da on the basis of both sodium dodecyl sulfate - polyacr ylamide gel electrophoresis and gel filtration chromatography.