Use of a monoclonal antibody against an Escherichia coli O26 surface protein for detection of enteropathogenic and enterohemorrhagic strains

A monoclonal antibody (MAb) was obtained from a mouse immunized with solubi lized outer membrane proteins extracted from a bovine enterohemorrhagic str ain of Escherichia coli (EHEC), O26, The MAb produced a strong immunoblot r eaction at approximately 21 kDa for an O26 strain containing the intimin ge ne (eae) and verocytotoxin (VT), but not with an O26 eae- and VT-negative s train, or O157 eae- and VT-positive strains. The MAb was used in a sandwich enzyme-linked immunosorbent assay (ELISA) format to screen strains from an imal and human sources, and all reactive strains were characterized for the presence of eae and the gene encoding VT factors by PCR, The antigen was d etected in a group of strains containing a high proportion of O26, the majo rity of which were eae positive with or without VT; these were isolated mos tly from animal enteritis cases but included a small number of human enteri c isolates. Nonreactors included eae-positive (with or without VT) O157 str ains and one O26 strain. In a survey of mixed cultures from both animal and human enteric disease, ELISA-positive reactions were obtained from 7.1 to 11.2% of samples from bovine, porcine, ovine, and human sources. The two hu man O8 and ten animal O26 ELISA-reactive pure strains obtained from these s amples contained six eae- and/or VT-positive strains; the other six strains lost their ELISA positivity following storage at -70 degrees C, after whic h none were found to contain either eae or VT factors. The association of t he antigen detected by the MAb with significant enteropathogenic E. coli an d EHEC virulence factors in isolates from both animal and human enteric inf ections indicates a diagnostic potential for the assay developed.