Listeria monocytogenes is a Gram positive bacteria, nonspore-forming, facultatively anaerobic, catalase-positive, oxidase- negative and expresses a beta hemolysin. It can grow in a wide range of temperatures 0-42^oC, with optimum between 30 and 35 ^oC.

 The genus Listeria includes seven different species (L. monocytogenes, L. ivanovii, L. innocua, L. welshimeri, L. seeligeri, L. grayi, and L. murrayi). Both L. ivanovii and L. monocytogenes are pathogenic in mice, but only L. monocytogenes is consistently associated with human illness.

The infection caused in humans is called Listeriosis. In pregnant women, it can often lead to abortion, premature birth or stillborn fetus. In sensitive population groups (young children and elderly) and in immunocompromised individuals, it usually appears as septicemia, meningitis and meningoencephalitis. It may also appear as endocarditis. Listeriosis in adults has a high mortality rate (up to 34%).

 A great number of cases of foodborne listeriosis have been reported, and L. monocytogenes is now widely recognized as an important hazard in the food industry.

 The European Union with its Regulation EC 2073/2005 sets microbiological criteria for L. monocytogenes in “ready to eat” food. Those foods has been classified in two categories depending on their ability to support or not, the growth of L. monocytogenes. In accordance with the above Regulation, the food business operator must be able to demonstrate, to the satisfaction of the competent authority, to which food category, with regards to the growth of L. monocytogenes, its product belongs. Also the food business operator may have to fix intermediate limits throughout the self-life of the product. The above procedure is part of the self-life study for “ready to eat” foods.

 In Tsakalidis Analysis & Testing we can evaluate the food category that your product belongs to (support or not the growth of L. monocytogenes) and estimate the growth rate of the microorganism to this particular food product. The test includes inoculation of the food with a L. monocytogenes strain and evaluation of the microorganism’s behaviour throughout the self-life of the product (Challenge test). At the end of the test, we will deliver a comprehensive report for your product, which will help you, if necessary, to adjust your production process, meeting the legislative requirements.

 In addition, it is well known that L. monocytogenes often exists in the production environment (e.g. equipment) and can contaminate “ready to eat” foods. The regular control of equipment and processing areas for the presence of L. monocytogenes is not only necessary but also mandatory (Regulation EC 2073/2005).

 The qualified staff of Tsakalidis Analysis & Testing may visit your production facilities and take samples of surfaces (Swab test) in order to check the presence or not of L. monocytogenes. This will confirm that the cleaning and disinfecting procedures of your business are adequate or not. 

Parameter	Method	Accreditation
Detection of Listeria monocytogenes	ISO 11290-1/A1:2004
Detection of Listeria monocytogenes	VIDAS LMO2
Enumeration of Listeria monocytogenes	ISO 11290-2/A1:2004
Swab Test	ISO 18593:2004
Challenge test	Guidelines by EURL for Lm