Development of a simple latex agglutination assay for detection of Shiga toxin-producing Escherichia coli (STEC) by using polyclonal antibody against STEC

Rabbit antiserum raised against the whole-cell antigen of Shiga toxin-producing Escherichia coli (STEC) strain VT3 (stx,(+) stx,(+) eae(+)) was repeatedly adsorbed with heat-killed cells of different non-STEC strains and other enteric bacteria. Thus, the antiserum obtained was designated VT3 antiserum. VT3 antiserum reacted with intimin type gamma. We assessed the reactivity of VT3 antiserum to whole-cell lysates of 87 strains of E. coli and other enteric bacteria by immunoblotting. The antiserum recognized the 97-kDa protein in whole-cell lysate from strain VT3, and 36 (83.7%) of the 43 STEC strains were positive for the STEC antigen. None of the non-STEC strains or strains of other species examined tested positive by immunoblotting. Based on this result, we developed a latex agglutination assay for the detection of STEC strains. Thirty-five (81.4%) of the 43 STEC strains tested positive for the STEC antigen by the latex agglutination assay. One (3.3%) of the 30 non-STEC strains and none of the strains of the other enteric bacteria included in this study tested positive by the latex agglutination assay. The corresponding specificity of the latex agglutination assay was approximately 98%. Results of this study showed the production of STEC antiserum and the generation of a simple, cost-effective, sensitive, and specific latex agglutination assay for establishing an etiological diagnosis of STEC.