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The BioStar® OIA® SHIGATOX assay is an Optical Immunoassay (OIA) test for the qualitative, rapid detection of the presence of Shiga toxins in human diarrheal fecal specimens, broth cultures, fecal specimens in Cary Blair Transport Media, or swab sampling of colonies from a culture plate. This test is intended for in vitro diaqnostic use as an aid in the diagnosis of infection by Shiga toxin-producing Escherichia coli (STEC) both O157 and all non - O157 Shiga toxin-producing strains.

The OIA SHIGATOX test involves the qualitative detection of Shiga toxins 1 and 2 (Stx1 and Stx 2) produced by certain strains of Escherichia coli and other organisms. The Optical ImmunoAssay technology enables the direct visual detection of a physical change in the optical thickness of molecular thin films. This change is the result of antigen - antibody binding on an optical surface (silicon wafer). After a specimen potentially containing Shiga toxin is mixed with conjugates and placed directly on the optical surface, the immobilized surface antibodies capture the antigen/conjugate complex. After washing, the substrate is added, increasing the thickness (mass enhancement) of the molecular thin film. This change in thickness alters the reflected light path, and this alteration is visually perceived as a color change. Slight changes in the optical thickness produce a distinct visible color change. A positive result appears as a purple spot on the gold background. When antigen is not present in the specimen, no binding takes place. Therefore, the optical thickness remains unchanged, and the surface retains the original gold color indicating a negative result. More specifically, the BioStar OIA SHIGATOX device is based on a novel thin film optical detection technology that relies on the interaction of white light with thin films to create a destructive interference phenomenon. Characteristic of this phenomenon is the generation of a reflective surface that changes color as a function of the change in optical thickness (refractive index x thickness) of the films on the surface of the device. To take advantage of this phenomenon for monitoring biological binding events, the optical surface with a special background color is coated with a capture reagent specific to the analyte of interest. In the OIA SHIGATOX device, the biological capture film is a combination of affinity-purified polyclonal antibodies to Shiga toxins 1 and 2 (Stx 1 and Stx 2). Samples suspected of containing either or both of the toxins are mixed with cocktail containing polyclonal antibodies to Stx 1 and Stx 2 that have been covalently conjugated to horseradish peroxidase (HRP). Once a sample containing toxins or either toxin is applied to the surface, the immune complex of toxin(s) and the anti-toxin-HRP conjugate(s) are bound to the surface antibodies. Following a wash step, a precipitating substrate for HRP is added, and a thin film generated by the immobilized immune complex is enhanced by the precipitation of the HRP product. Once washed and dried, a simple color change relative to the gold background color is observed as an indication of the presence of Stx 1 or Stx 2 in the original specimen. The OIA SHIGATOX device produces a qualitative result for the presence or absence of Shiga toxin as the device output. Input to the device is the simple addition of an aliquot of fecal material (direct or in transport media) or broth culture to the reagents contained in the kit. Fecal samples are routinely collected and no special collection requirements exist. Test devices within the kit are single use devices, and disposal instructions are provided in the Package Insert. The kit contains all components necessary for analysis of the range of samples approved for use in this product, with the exception of a timer.