Analytical methodology to detect ricin and Shiga toxins (Stx) in food matrices is important because of the potential use of ricin in food as a terrorist weapon, and the presence of Stx in food as a naturally occurring contaminant resulting from its production by Shiga toxin-producing strains of Escherichia coli that can lead to serious foodborne disease outbreaks. Monoclonal antibodies (mAbs) that bind each toxin were used for capture in sandwich enzyme-linked immunosorbent assay (ELISA), and IgY polyclonal antibodies were prepared from the eggs of immunized hens for use as detection antibodies. IgY was detected using horseradish peroxidase (HRP)-conjugated anti-IgY and colorimetric or chemiluminescent substrates. The IgY antibodies obtained were effective for detection of toxins, but did not function well for �capture� in the sandwich format. The assay systems detect pure ricin or crude ricin-containing castor extract, but do not significantly respond to isolated ricin chains, heat-denatured ricin, or the related agglutinin, Ricinus communis agglutinin 1 (RCA-1). The lower limit of detection was 0.1 � 0.2 ng/mL for milk samples containing 0- 4% fat, with recoveries of approximately 60%. Using standard 96-well plate formats, the assays detect less than 1 millionth of an adult human lethal dose. The assay systems produced excellent recoveries in the ground beef matrix, with sensitivities of about 0.5 ng/g. For the detection of Stx2, IgY ELISAs detected active, but not heat-denatured Stx2, at 0.1 � 0.2 ng/mL, with recoveries of 70 � 80%.

Immunosorbent analysis of ricin and Shiga toxin contamination in milk and ground beef using IgY-based ELISA with colorimetric or chemiluminescent detection

248th National Meeting (2014)

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