Listeriosis is an infection caused by the bacterium Listeria monocytogenes, a microorganism with a natural habitat in soils, plants and water. If ingested in large quantities through contaminated food, this bacterium can give very serious consequences on humans.

It is therefore essential to prevent the contamination of food surfaces by using specific cleaners and by following accurate cleaning procedures that can be easily adopted by any food and beverage producer.

For this reason, national legislations have set limits to the count of Listeria monocytogenes in food and beverages outcoming from production plants. In some countries, such as the United States of America, there is no tolerance for the presence of this microorganism. Of course, the limits imposed in the United States are also valid for producers of other countries who want to export in this country, and therefore the organizations which authorize these movements of goods put a lot of pressure in order to have foodstuff totally free from Listeria.

How listeria contamination occurs

As it lives on the grounds and in surface waters, it is with raw materials that Listeria enters food plants. It is a microorganism that does not have great resistance to high temperatures or other antimicrobial treatments; however, it tolerates high saline levels and is able of multiplying even at low temperatures. Moreover, in the last years, it has been known that Listeria is not only capable of surviving inside biofilms formed by other microorganisms, but it is itself a biofilm promoter.

Protected by biofilm, it becomes little sensitive to disinfection treatments and it multiplies undisturbed continuing to contaminate food and beverages with which it comes in contact.

To summarize, it is important to consider these factors when drawing sanitation procedures to be adopted in the production plants:


The microorganisms can anchor themselves to surfaces only if on them there are traces of organic matter and mineral cations that allow anchorage and protection.

Only adequately sequestered and surfactant-activated cleaning solutions avoid the deposits listed above and thus prevent the first phase of biofilm formation.

Washes carried out with simply caustic solutions (e.g. only soda) do not have the ability to remove inorganic residues from surfaces.

These concepts derive from the universally valid laws of thermodynamics.