Antigenic cross-reactions between Escherichia coli O157, Vibrio cholerae O1 (Inaba) and group N salmonella

Lipopolysaccharide antigen-antibody cross-reactions between Escherichia coli O157 and other members of the Enterobacteriaceae were examined. Using serotyping schemes established in the Laboratory of Enteric Pathogens (LEP), cross-reactions were demonstrated between E. coli O157, Vibrio cholerae O1-Inaba and group N (O = 30) salmonella. SDS-PAGE and immunoblotting showed that the lipopolysaccharide (LPS) of E. coli O157 contained epitopes shared with LPS expressed by group N salmonella. These cross-reactions were also detected using sera from patients with haemolytic uraemic syndrome (HUS) caused by E. coli O157:H7. Rabbit antibodies, prepared to the LPS of V. cholerae O1-Inaba reacted with the LPSs of both E. coli O157 and V. cholerae O1-Inaba, whilst rabbit antisera prepared to E. coli O157 did not react with the LPS of V. cholerae O1-Inaba. Antibodies in sera from patients with HUS, which reacted with the LPS of E. coli O157, did not react with the LPS from V. cholerae O1-Inaba. We concluded from our study that cross-reactions between E. coli O157 and other bacterial species are rare; and that patients infected with bacteria known to share epitopes with E. coli O157 are unlikely to give false positive results when their sera were tested for E. coli O157 serology.