Designing of immunodiagnostic assay using polyclonal antibodies for detection of Shiga toxin producing pathogenic E. coli ({STEC}) strains

Shiga toxin-producing Escherichia coli (STEC) are the leading causes of diarrhea and death of humans worldwide. Many diagnostic assays have been developed to aid for the diagnosis of STEC strain; however, they have limitations. Thus, this study was aimed at designing rapid, effective, sensitive and specific immunodiagnostic assay for STEC strain detection. Thus, a STEC isolate from Ethiopia was processed for LPS extraction and the LPS was used to immunize mice.. The produced antibody showed positive agglutination both on the purified LPS as well as the STEC isolate carrying LPS on their surface; however, agglutination of STEC was more pronounced. Mice immunized with LPS produced highest agglutination on tertiary immunization showing the progressive buildup of the antibody response against the antigen. Cultures from tryptone soya agar and when they refresh showed better agglutination than cultures on EMB as well as tryptone soya broth. Immunodiagnostic assay developed in this study could detect STEC strains including STEC in human feces rapidly (1-2 min), with high sensitivity (90.2%), specificity (89.5%) and accuracy (90.6%). However, further studies are still required to improve the sensitivity, specificity and reproducibility. Overall this diagnostic assay provided promising results that may curb current problem with detection methods in clinical health care and research laboratories.