Listeriosis, an infection associated mainly with the consumption of food contaminated by the bacterium Listeria monocytogenes.

Although less common than other food-borne diseases, such as salmonellosis and campylobacteriosis, it has the highest hospitalization and mortality rate of all zoonoses.


In most people, listeriosis occurs in a mild form, with flu-like symptoms (symptoms) that resolve within a few days without the need for treatment.

However, in people with a weakened body's defense system (immunosuppressed) due to diseases (for example, HIV) or treatments (chemotherapy, cortisone therapy) and in the elderly, the infection from the intestine can spread to other parts of the body and cause serious complications (invasive listeriosis). In invasive listeriosis, the most frequent disorders are fever, meningitis, meningoencephalitis, septicemia, localized infections (arthritis, endocarditis).

In pregnant women, listeriosis occurs in a mild form but through the placenta it can be transmitted to the fetus with serious consequences (abortion, fetal death, premature birth and, in the first month of life of the newborn, meningitis, meningoencephalitis, septicemia).


Listeriosis is named after the bacterium that causes the infection, Theresteria monocytogenes. The bacterium is widespread in the environment and can be present in the feces of animals and humans even if they do not have disorders (symptoms). It can also be easily found in the environments where food is produced and can contaminate them at every stage of their production / transformation.Since the microorganism is sensitive to heat, the foods most at risk are raw ones (vegetables, raw milk cheeses) and those which, after treatments such as pasteurization, cooking or smoking, are contaminated during slicing / portioning and packaging. .

Unlike many other bacteria, the Listeria monocytogenes it can multiply at temperatures around 4 ° C. This characteristic makes ready-to-eat foods particularly at risk, i.e. those that do not require cooking / heating treatments before being eaten, since the bacterium could multiply and reach potentially dangerous levels during refrigeration.

The possibility that Theresteria monocytogenes multiply in food is also linked to their physico-chemical characteristics. Drier and more acidic foods (eg aged cheeses, aged cured meats) hinder its multiplication, compared to wetter and less acidic foods (eg fresh cheeses, smoked salmon) which, on the other hand, favor its growth.


Antibiotic treatment (therapy) for listeria monocytogenes it is represented by the administration of ampicillin or, in case of allergy to it, of erythromycin.


The best way to prevent listeriosis is to follow good hygiene rules when preparing / handling food:

  • always and thoroughly wash your hands after going to the bathroom (Video)
  • wash your hands before and after preparing food
  • wash vegetables and fruits thoroughly, even before they are peeled
  • wash kitchen surfaces and utensils, especially after preparing raw meat, poultry and eggs
  • always separate raw foods from ready-to-eat foods
  • cook food thoroughly, checking the cooking instructions (time and temperature)

The precautions relating to "ready-to-eat" foods include:

  • do not eat the food after the expiry date expressed with the words "to be consumed by .."
  • make sure that the temperature of the domestic refrigerator does not exceed 4 ° C
  • follow the storage instructions on the product labels

Advice intended for people who are at increased risk of getting listeriosis (the elderly, pregnant women, children under one month of age and people with a weakened immune system due to disease or treatment) constitute an "additional form of prevent contagion. They plan to avoid the consumption of foods known to be at high risk of contamination:

  • soft cheese with mold on the surface, such as Brie, Camembert
  • soft cheese with mold in the mass, such as gorgonzola
  • all types of pate
  • raw milk
  • smoked salmon
  • slightly seasoned cold cuts
  • undercooked foods

Given the importance of an adequate calcium intake, pregnant women can eat aged cheeses (Parmesan, pecorino), even if made with raw milk, since prolonged aging reduces / eliminates any initial contamination.
Pregnant women should avoid close contact with farm animals.


Acciari VA, Iannetti L, Gattuso A, Sonnessa M, Scavia G, Montagna C, Addante N, Torresi M, Zocchi L, Scattolini S, Centorame P, Marfoglia C, Prencipe VA, Gianfranceschi MV. Tracing sources of Listeria contamination in traditional Italian cheese associated with a US outbreak: investigations in Italy. Epidemiology and Infection. 2016; 144 : 1719-27

Gianfranceschi M, Gattuso A, Fiore A, D "Ottavio MC, Casale M, Palumbo A, Aureli P. Survival of Listeria monocytogenes in uncooked Italian dry sausage (salami). Journal of Food Protection. 2006; 69 : 1533-8

National Guidelines System (SNLG). Physiological pregnancy

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