O 157 is also associated with thrombocytopenia and microangiopathic hemolytic anemia. Other complications include colonic stricture, chronic pancreatitis and irreversible cognitive impairment. It is increasingly recognized that non-O157 E coli can cause a similar syndrome. There is a lower incidence of bloody diarrhea and less HUS associated with this strain. However, if it carries the eaeA gene, the incidence of protracted or bloody diarrhea and HUS markedly increases.
Diagnosis begins with stool culture.
Fecal leukocytes are often positive, but a negative result does not rule out the diagnosis. If stool is obtained early in disease, the diagnosis can be made by Sorbitol-MacConkey agar. E coli O157 are colorless colonies on this media because they don't ferment sorbitol, unlike most other E. coli. These colonies can then be assayed for O157 antigen. Non-O 157 do ferment sorbitol, and are very difficult to diagnose.