Escherichia coli are bacteria that live in the intestines of people and animals. Shiga toxin-producing E. coli or STEC makes toxins that can cause severe illness. Non-O157 STEC strains are increasing recognized as important foodborne pathogens worldwide. With E. coli O157:H7, six STEC serogroups (O26, O45, O103, O111, O121, and O145) are now regulated as adulterants in certain raw beef products in the United States. However, effective detection and isolation of non-O157 STEC strains from food matrices still remain challenging. Current detection methods including real-time PCR, enzyme immunoassay (EIA) in addition to traditional culture on sorbitol MacConkey agar are used. Although each method has advantage over others in terms of specificity and sensitivity, current methods have limitation to implement for rapid detection with high volume of samples. Surface plasmon resonance imaging (SPRi) is an emerging optical technique, which allows for rapid and label-free screening of multiple targets simultaneously. We have evaluated the potential of SPRi in label-free detection of Shiga-toxins (Stx1, Stx2) produced by E. coli. Corresponding antibodies were attached to the gold (50 nm) sensor surface through mercaptoundecanoic acid monolayer and carbodiimide crosslinking, and subsequently blocked with 1% skim milk proteins. Shiga-toxins were detected by SPR sensorgram analysis and difference images between targets and reference. Satisfactory ligand immobilization was achieved at 1 mg/mL Stx1 and Stx2 antibody concentrations. Upon regeneration with a relatively mild buffer (10 mM glycine-HCL pH 2.5), significant ligand loss was observed. Overall we demonstrated potentials of SPRi method for high-throughput and multiplex food safety detection.

Shiga toxin detection with label-free surface plasmon resonance immunosensor

256th National Meeting (2018)

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