Sporadic cases of hemorrhagic colitis associated with Escherichia coli O157:H7. Clinical, epidemiologic, and bacteriologic features.

During a 6-month period in 1983, Escherichia coli O157:H7 was isolated from 19 (15%) of 125 patients with grossly bloody diarrhea and 1 sibling with non-bloody diarrhea in the Calgary area. There was no clustering of the cases geographically or in time. All but 1 had clinical manifestations typical of hemorrhagic colitis associated with E. coli O157:H7. The illness appeared to be associated with consumption of hamburgers by 15 patients. The diarrheal illness was usually self-limited, but 3 children developed the hemolytic-uremic syndrome shortly after onset of illness. The organism was excreted in the stools very briefly in adults, although bacterial shedding continued for a longer period in children. All isolates produced verotoxin, and cytotoxic activities were present in stool filtrates. The results suggest that the incidence of sporadic cases of hemorrhagic colitis due to E. coli O157:H7 may be higher than has been suspected, and that patients with grossly bloody diarrhea should be studied promptly for E. coli O157:H7 infection. Specific techniques for identifying this serotype must be applied to the stool cultures. Detection of free cytotoxin in stool filtrates may be an effective diagnostic procedure.