This system utilizes Listeria enrichment single-step (LESS) medium to selectively enrich Listeria species present in food and environmental samples.

This system also uses Half Fraser Broth Plus and buffered Listeria enrichment broth (BLEB) to selectively enrich for Listeria species in select food matrices.

A sample (200 µL) equilibrated to room temperature after heat-kill of the enrichment culture is placed into the sample cup. The test device is placed into the sample and allowed to develop at ambient temperature for 20 minutes. The sample is wicked through a reagent zone that contains specific anti-Listeria antibodies conjugated to colloidal gold particles. If antigens are present in the sample, they will bind to the gold-conjugated antibodies. This antigen-antibody complex then leaves the reagent zone and travels through the nitrocellulose membrane, which contains a zone of anti-Listeria antibodies. The immune complex with gold conjugate is captured and aggregates in this zone, thus displaying a visible line. The remainder of the sample continues to migrate to the end of the membrane where it is deposited into a waste reservoir.

The reagent zone also contains gold conjugate of a proprietary antigen that is eluted by the sample solution regardless of the presence of Listeria antigen. The gold-conjugated control indicator migrates through the membrane to the control capture zone (antibody to the proprietary antigen), where it is captured and aggregated to form a visible line. In the presence or absence of the Listeria antigen, the control line will form in the control zone, ensuring the test is working properly.