Serodiagnosis by passive hemagglutination test and verotoxin enzyme-linked immunosorbent assay of toxin-producing Escherichia coli infections in patients with hemolytic-uremic syndrome.

Eight cases of hemolytic-uremic syndrome in which no pathogens were isolated were diagnosed serologically by a passive hemagglutination assay and a verotoxin (VT; Shiga-like toxin) enzyme-linked immunosorbent assay (ELISA). The passive hemagglutination assay employed formalinized sheep erythrocytes sensitized with soluble native antigen or heat-treated antigen (lipopolysaccharide [LPS]) from Escherichia coli O26, O111, O128, and O157 or flagellar antigen of nine different H serogroups of E. coli: H2, H7, H8, H10, H11, H12, H18, H19, and H25. All patients had antibodies against the native antigen and/or the LPS of E. coli O157, but positive agglutination with H7 was observed only in one patient. In the VT-ELISA with plates coated with purified VT 1 or VT 2, antibody against VT 2 was observed in the sera of five of six patients examined, but none of the patients possessed VT 1 antibody. These results indicate that the causative pathogen in these eight hemolytic-uremic syndrome cases is likely to be VT-producing E. coli O157. The passive hemagglutination assay described here is a very sensitive, simple, and rapid method. This assay is highly recommended for the serological diagnosis of VT-producing E. coli infections, particularly in patients infected by serogroup O157 strains. Furthermore, the VT-ELISA is useful in studying the role of VT in hemolytic-uremic syndrome.