Listeria is a family of bacteria consisting of several species, among them Listeria monocytogenes is the only pathogenic.
L. monocytogenes is a ubiquitous bacterium since it can be present in soil, water, vegetation and it can contaminate food, especially milk, vegetables and fruits, soft cheese, meat and fish. The primary source of contamination and route of transmission to humans is food.
Unlike other bacteria, L. monocytogenes grows well and can multiply even at very low temperatures, in a salty and both aerobic and anaerobic environments; on the other hand, it does not survive at temperatures above 65 °C, which can be easily reached even at home.
Although the disease caused by L. monocytogenes, Listeriosis is rare but it can cause fever, nausea, vomit, and diarrhea as well as severe symptoms that in the most vulnerable individuals also lead to meningitis and death.
Regulatory requirements
In the European Union, Commission Regulation (EC) no. 2073/2005 defines the microbiological criteria applicable to food products.
Even in the United States, the Department of Agriculture’s Food Safety and Inspection Service (FSIS) has a zero-tolerance policy for the presence of L. monocytogenes in ready-to-eat meat and poultry products and continues to strengthen programs and recommendations to reduce or eliminate the bacterium from RTE products.
Preventive measures
In order to prevent the development of L. monocytogenes in food, good handling, formulation and hygiene practices must be followed as well as strict temperature controls throughout production, distribution and storage chains –including at home– must be implemented.
Food alerts: a look at recent years
Recently, several cases of Listeriosis have been reported in different Italian regions due to food contamination, particularly of meat products. According to Mérieux NutriSciences Safety HUD, food alerts and fraud monitoring tool, 1,700 alerts were notified since 2020 in meat and derivatives, poultry, milk and derivatives, fish and derivatives and ready to eat products.
Clearly, the ubiquity and the ability of L. monocytogenes to survive even at refrigeration temperatures and in both aerobic and anaerobic conditions increase the risks of contamination and cross-contamination throughout the supply chain; this can also result in epidemic outbreaks, especially by ready-to-eat products.
Mérieux NutriSciences support
As a global partner for the food industry, Mérieux NutriSciences provides up-to-date data on food alerts and frauds, and supports companies from an analytical point of view.
Our microbiology laboratories also offer high-level analytical solutions thanks to quick methods for the qualitative determination of pathogens such as Salmonella spp., Listeria spp. and L. monocytogenes and eventually plate quantification in CFU/g to control the microbiological safety of food products and preserve consumers’ health.