Assay detects Listeria in ready-to-eat products

The assay allows food companies to detect environmental Listeria spp in less than eight hours - saving more than two days on traditional detection methods and allowing problems to be swiftly identified, ultimately helping companies avoid product recalls and processing line shutdowns.

With the BAX system eight-hour Listeria assay, results from environmental samples can be available the same day they are taken.

If the result is positive, there is only a limited amount of production to be concerned about, meaning the problem can likely be identified and resolved before the next shift begins.

Oxoid said this speed will be of particular value to manufacturers of short-shelf-life, ready-to-eat products, including chilled meals, cooked meats, smoked fish, bagged salads and dairy products.

The reverse-transcriptase PCR assay allows for detection of Listeria at concentrations as low as 10cfu/ml.

Samples do not require the normal enrichment period, which can range from one to several days.

Listeria cells are simply resuscitated by incubation in a specific collection buffer for four hours.

Then, following a short reverse-transcriptase step - which gives a jump start to the PCR replication process - samples are loaded into the BAX system cycler/detector for processing.

Results are automatically interpreted by the system's user-friendly software and displayed on-screen using positive (red) or negative (green) icons.

In validation studies, the performance of the BAX system eight-hour Listeria assay was superior to the reference USDA FSIS culture method in the detection of Listeria from stainless-steel surfaces.

Using a panel of 58 Listeria strains, across the seven species of Listeria, and 52 non-Listeria strains, the assay demonstrated 100 per cent inclusivity and exclusivity.

The BAX system eight-hour Listeria assay has been approved and certified by the AOAC Research Institute.