[Serum anti-lPS antibody production in an outbreak of enterohemorrhagic Escherichia coli O157 infection among schoolchildren].

Although there have been many reports of the usefulness of serodiagnosis of enterohemorrhagic Escherichia coli (EHEC) O157, the serotype of the bacteria detected and the increase in anti-LPS antibody have not always been consistent. In this study we investigated the diagnostic significance of measurements of anti-LPS antibody by ELISA in an outbreak of O157 infection among schoolchildren in whom the bacteriological test findings were clarified and the age groups were uniform. The anti-LPS antibody titer was measured in 31 patients (77 serum samples) in an outbreak of EHEC O157 : H7 infection (220 children infected) that occurred in a primary school in Morioka in 1996. The anti-O157 LPS antibody positivity rates of IgM, IgG, and IgA were 98.7%, 85.7%, and 98.7%, respectively. Between the time the meal that caused the outbreak and 19 days later, anti-O157 LPS IgM antibody and IgA antibody were detected in all patients. The specificity was investigated using control serum, and the specificity of IgM, IgG, and IgA was 93.5%, 93.5%, and 97.2%, respectively. Some samples contained antibodies against O111 and O26 LPS, but the titers were lower than the anti-O157 antibody titer. The anti-O111 antibody titer and anti-O26 antibody titer were highly correlated, suggesting that they were crossreactive antibodies for O157 LPS. No significant correlation was found between differences in clinical manifestations and the anti-O157 LPS antibody titer in this O157 outbreak in schoolchildren. It was clarified that an increase in anti-LPS antibody was found to support the diagnosis of mild cases of 0157 infection infection as well as severe cases.