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The new test card RIDA^®COUNT Salmonella/Enterobacteriaceae has been developed for detection of Salmonella from food and feed samples as well as samples from the production environment. In addition to the detection of Salmonella the user has the option to record and differentiate other Enterobacteriaceae.

While for the detection of Salmonella in food samples a pre-enrichment according to ISO 6579:2002 has to be performed the detection of Enterobacteriaceae could be done directly from the food homogenate or suitable dilution. For hygiene monitoring on surfaces RIDA^®COUNT Salmonella/Enterobacteriaceae test cards can be directly applied to the surface to detect and quantify Salmonella or total Enterobacteria.

RIDA^®COUNTs are non-woven membrane culture medium sheets in a ready to use test card format. The card is multi-layered, built up from a base followed by the nutrient layer and topped with a layer of inert polymer to absorb the test liquid. A non-woven fabric layer makes up the final top surface and ensures the structural stability of the test card. Easy counting of developing colonies is facilitated by a plastic foil covering that has an integrated counting grid.
The detection technique of RIDA^®COUNT Salmonella test cards is based on modified VRB (Violet Red Bile) medium containing the chromogenic substances X-α-Gal and Salmon-β-Gal.
Bile salts inhibit Gram-positive bacteria. The substrate X-α-Gal is reduced by α-galactosidase an enzyme specific for Salmonella. The substrate Salmon-β-Gal is reduced by β-galactosidase which is not produced by Salmonella though the majority of Enterobacteriaceae can do. The formation of blue colonies on the test card typically shows Salmonella colonies while all other colours from magenta to purple or indigo indicate the presence of other Enterobacteriaceae.

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