Serological Methods for the Detection of STEC Infections

The detection of antibodies to Shiga toxin (Stx)-producing Escherichia coli (STEC) antigens serves varied purposes: (1) the etiologic diagnosis of acute hemolytic uremic syndrome (HUS) and hemorrhagic colitis (HC) in the clinical laboratory; (2) epidemiological investigations; (3) the study of immune responses in STEC-mediated diseases, immunization trials, and animal models. Although the isolation of STEC from the feces of a patient with HC or HUS is generally sufficient evidence for its etiological role in these diseases, it may fail because of a number of circumstances. For example, a timely stool specimen may not be available, the primary laboratory may be unaware of the clinical diagnosis or apply inadequate isolation methods, or the patient may have received suppressive antibiotics. Moreover, when patients present with HUS, usually 5-7d after the onset of diarrhea, the excretion rate of STEC organisms is already substantially diminished. Among E. coli isolates from patients with HUS and HC, STEC O157:H7 predominates. However, so-called non-O157:H7 STEC serotypes are emerging both as causes of outbreaks and sporadic HUS and diarrhea, especially in Europe, Australia and South America. The clinical features of non-O157 STEC infections closely resemble those of prototypic E. coli O157:H7 disease (1 ,2 ). The microbiological diagnosis of non-O157:H7 STEC strains is complicated by the lack of easily detectable biochemical or growth characteristics and large serotype diversity. Serological techniques offer a complementary, culture-independent diagnostic approach. They are indispensable for epidemiological and immunization studies.