Listeria - If Cold is not Cold Enough

The ability of certain groups of bacteria, and in this case, Listeria spp, to multiply at low temperatures is highly significant from a food hygiene viewpoint. Storing food at low temperatures typically prevents growth of food pathogens, but there is considerable evidence to indicate that this is not the case for Listeria spp.

The Genus Listeria comprises 6 different species, but only L. monocytogenes is generally pathogenic to humans. Listeriosis is an invasive infection caused when contaminated food is ingested. Symptoms vary, ranging from flu-like symptoms to meningitis and encephalitis. The mortality rate for Listeriosis is approximately 23% which, compared to other food poisoning, is very high.

Despite only Listeria monocytogenes being pathogenic to humans, all Listeria species serve as indicators of improper hygiene conditions. It is claimed for example, that a minimum of one food in each fridge is contaminated by Listeria.

Listeria spp. are ubiquitous and a wide variety of food types, such as milk, meat or fish products, can be effected. Not even vegetables can escape being Listeria-free. New technologies, such as cook-chill, and new technologies to extend the shelf life of food could lead to increasing problems with Listeria. Therefore, special care must be taken over the complete food production chain to implement proper hygiene conditions and so prevent contamination with Listeria.

With Merck's comprehensive product range, you are guaranteed to find the product combination which makes the detection of Listeria spp. and Listeria monocytogenes easy, fast and reliable for you.

Regardless of whether you are using the classical media methods, or innovative new methods, such as real time PCR or lateral flow tests, you will guarantee that you are always on the safe side.

Regulation
The following is a summary of Listeria media specified by different regulatory authorities.