THE JOURNAL OF INFECTIOUS DISEASES · VOL. 146, NO.6. DECEMBER 1982 Production of Shigella dysenteriae Type J-Llke Cytotoxin by Escherichia coli

Strains of Escherichia coli previously implicated or proven to be causes of diarrhea were examined for production of a toxin similar to that of Shigella dysenteriae type I (Shiga). Organisms grown in an iron-depleted broth were lysed by pressure disruption followed by ultracentrifugation. Saline-dialyzed extracts were tested for cytotoxic effects on HeLa cells that were neutralizable with antiserum to Shiga toxin. Among the 13E. coli strains so analyzed, 11 made a Shiga-like cytotoxin in levels ranging from trace (two avirulent isolates) to amounts equivalent to S. dysenteriae type 1 (two noninvasive strains that did not make E. coli heat-labile or-stable enterotoxins but were isolated from infants with diarrhea). As with extracts of Shiga toxin, lysates of these E. coli strains that produced high levels of Shiga-like toxin were enterotoxic for rabbits, paralytic and lethal for mice, and inhibited protein synthesis in HeLa cells. Thus, these data suggest that Shiga-like toxin may be another heretofore undiscovered factor in the pathogenesis of diarrhea caused by some E. coli strains. Two mechanisms have been described by which Escherichia coli can cause diarrheal disease in hu