Listeria

Listeriosis is a disease caused by the bacterium Listeria monocytogenes. Contamination occurs through the ingestion of foodstuffs contaminated by this pathogen. In at-risk persons, it can evolve into serious forms (a blood or brain infection) that can sometimes lead to death. In pregnant women, the infection can cause miscarriage, premature delivery or an infection in the newborn baby. Listeriosis is treated with antibiotics.

How do you become contaminated by the bacterium?

Listeriosis is usually caused by the consumption of food contaminated by Listeria monocytogenes. If an infection occurs during pregnancy, the bacteria can spread to the baby through the placenta.

Who is at risk?

Mainly people with lower immunity:

  • pregnant women
  • immunocompromised patients (suffering from cancer, diabetes or receiving immunosuppressive therapy)
  • the elderly.

The infection rarely affects people outside of these at-risk groups.

How can you reduce the risks of being contaminated by Listeria?

In 2016, the Superior Council of Health published a list of the foodstuffs to be avoided by at-risk people:

  • fresh cheese (mascarpone, etc.) and soft cheese (brie, etc.) made with raw or pasteurized milk
  • cooked meats (pre-packaged or pre-sliced) 
  • cold smoked fish 
  • cut and pre-packaged leafy vegetables (lettuce, herbs, spinach) 
  • sprouted seeds
  • pre-packaged cut melon or melon fruit salad 
  • raw meat and raw fish 
  • sandwich spreads with a mayonnaise base (chicken curry, meat salad, salmon salad, etc.) 
  • pre-packaged filled sandwiches or meal-sized salads (with cooked ham, smoked salmon, soft cheese, etc.)

It is also important to:

  • clean your fridge regularly
  • avoid eating food past its best-by date
  • ensure that the fridge temperature is low enough (<4°C)
  • wash food properly 
  • practice good hygiene when preparing food 

How is listeriosis diagnosed?

Listeriosis is usually diagnosed when in the form of a bacterial culture (laboratory test) of L. monocytogenes grown from a tissue or bodily fluid (like blood or spinal fluid).

Why is it so difficult to prevent foodborne diseases caused by L. monocytogenes?

After consuming contaminated foodstuffs, there may be a long incubation period before symptoms become apparent. It is therefore very difficult to make a connection with the food item consumed. 
A molecular database of the strains found in our food and in patients enables us to detect the source more efficiently.

Are veterinarians and farmers an at-risk group?

Skin infections have rarely been reported among veterinarians and farmers after direct contact with an animal.

Is there any specific legislation regarding Listeria monocytogenes in food?

Food safety criteria are set out in European Regulation 2073/2015.

Information for health professionals

Every two years, Sciensano’s Epidemiology of Infectious Diseases service publishes a report on the diseases related to various foodborne pathogens, including Listeria.


 

Sciensano collects data on listeriosis to determine the impact of this pathogen on the health of the population and to monitor the long-term pattern of its behavior. Sciensano detects L. monocytogenes in food and performs the tasks related to the NRL as requested by Europe and the FASFC.

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