Serological diagnosis of enterohaemorrhagic Escherichia coli(EHEC) infection by passive hemagglutination assay

: The passive hemagglutination(PHA) assay was developed to diagnose enterohaemorrhagic Escherichia coli(EHEC) infections serologically and was evaluated for the utility. The PHA assay was done using formalinized sheep erythrocytes sensitized with 2 kinds of antigens; soluble native and heat-treated antigens, by a microtiter method. A total of 63 serum samples from 33 HUS patients and 30 sporadic hemorrhagic colitis were subjected to the assay. For the control, 30 serum samples from 20 healthy adults and 10 healthy children were used. Thirty-two of 33 HUS patients had the antibody against soluble native antigen and/or heat-treated antigen of EHEC O157. These response was also observed in 14 HC cases with stool culture positive for EHEC O157. Good antibody response was observed against soluble native antigen than that against heat-treated antigen. The PHA titers distributed between 1:100 and 1:8,100 were observed in the samples taken in about 1 week or more after the onset of diarrhea, and the higher titer were observed in HUS patients than in HC patients. All of control sera were negative. The PHA assay described here is highly sensitive, simple and rapid method, and is recommended for the serological diagnosis of EHEC infections.