What is it ?
Listeriosis is an infectious disease of bacterial origin. It is an infection caused by the bacteria: Listeria monocytogenes . This pathology can have a serious character. Indeed, the infected individual may be suffering from sepsis (generalized infection of the body through the passage of the bacteria through the blood vessels) or infection of the brain.
An infection with Listeria monocytogenes in pregnant women is even more serious in the sense that it can cause abortion, neonatal infection or premature delivery.
The prevalence in France (number of cases of the disease in a given population at a given time) is low: 5 / 1,000,000. However, there is a 20 to 30% risk of death of the infected person. The risk of infection should not be neglected.
Cases of Listeria monocytogenes infections are usually sporadic cases, which mean that the disease affects only certain people randomly and without any contagion.
Beyond the fact that listeriosis can be more serious in pregnant women, some populations of people may also have a privileged ground for the development of the bacteria. These are:
– elderly people;
– people with underlying diseases (cancer, diabetes, immunodeficiency, autoimmune disease, etc.);
– people who have undergone organ transplants.
The most common symptoms associated with the disease are: digestive disorders, diarrhea, etc.
The bacterium involved: Listeria monocytogenes is a ubiquitous bacterium (present throughout the environment and very resistant). The bacterium is called “psychrophilic”, or it is able to grow at very low temperatures (refrigerators) but is destroyed during cooking. In this sense, this bacterium can be present in silage and thus contaminate ruminants. In addition, the bacterium is mainly present in the environment through the excrements of healthy and sick animals.
Animals infected with L. monocytogenes therefore constitute the predominant source of contamination for humans by this bacterium.
The bacterium’s potency in the environment allows it to contaminate a number of foods. Thus, exposure to L. monocytogenes is common but does not necessarily cause severe symptoms (usually digestive and diarrheal disorders).
Symptoms of listeriosis
The general symptoms associated with listeriosis are primarily intestinal and gastric: digestive disorders, diarrhea, abdominal pain, etc. Fever and body aches may also occur as a result of these primary symptoms.
In the case where the diagnosis of L.monocytoges infection is made, the form of the disease is called invasive. This form can result in:
– neurological damage: headache, nausea, fevers, vomiting, behavioral disorders that may lead to the development of meningitis or meningoencephalitis;
– a bacteremia: either the passage of the bacteria in the blood causing fever or chills;
– spontaneous abortions in the first half of pregnancy, premature delivery during an infection between the 6th and 9th week of pregnancy or even a fetal death.
– febrile gastroenteritis or bacteremia in patients with prostheses may also be associated with the disease but remain rare.
There is no symptomatic specificity of the disease but the symptoms vary from one patient to another.
In a healthy individual, contamination with L. monocytogenes may cause no symptoms or even cause transient febrile gastroenteritis.
It is therefore in “fragile” people (elderly people, immunocompromised, pregnant women, etc.) that the disease can prove to be severe. It is expressed by the development of meningitis, bacteremia, isolated fevers, spontaneous abortions, etc.
It is remarkable that in the pregnant woman, the infection is generally of no consequence for the mother or can be translated only through febrile periods. In addition, the newborn can be affected through cutaneous manifestations, respiratory abnormalities or neurological signs.
The origins of the disease
The main source of L. monocytogenes contamination is food. The transmission of the bacteria is mainly during the ingestion of contaminated food.
Transmission by direct contact with the animal or nosocomial transmission (infection during a hospital stay) is possible but are rare.
The placenta is not a barrier for the fetus, the transmission from the mother to the child is mainly by this route or by the genital sector during childbirth.
Food contamination by these bacteria can occur at any stage of the food chain: breeding, production, storage, preparation, storage, etc. Moreover, it concerns both the artisanal and industrial production chains.
Contamination with L. monocytogenes is increased by ingestion of raw or undercooked foods, mainly meats, smoked fish, vegetables, raw milk or raw milk cheeses.
The psychrophilic nature of this bacterium gives it the power to grow at 4 ° C (temperature of refrigerators). The lengthening of the cold chain can therefore promote the development of the bacteria and be a risk factor for additional contamination.
Risk factors for listeriosis
The main risk factors for L. monocytogenes contamination are:
– the lengthening of the cold chain;
– the consumption of raw or undercooked foods;
– poor hygiene during the various stages of the food chain (production, storage, preparation, etc.).
Prevention and treatment of listeriosis
Listeria monocytogenes is a ubiquitous bacterium, its presence in the environment and its increased resistance to it leads to a significant exposure rate for individuals.
Many people exposed to the bacteria have no symptoms or symptoms similar to gastroenteritis. In this case, the diagnosis is difficult to achieve.
Nevertheless, in the case where the symptoms are persistent, the isolation of the bacterium makes it possible to ask or not the diagnosis. This bacterial detection is based on a blood culture (culture of blood cells), from cerebrospinal fluid following a lumbar puncture, following vaginal sampling, placenta or gastric fluid.
Hospitalization of the subject affected by the patient often follows the diagnosis of the presence of the bacteria in the body.
The general treatment of listeriosis is essentially based on antibiotic therapy.
The vital prognosis for this pathology amounts to 20 to 30% for the weakened subjects and is often better in the young people and without antecedent.
Prevention is a very important concept in this context to avoid contamination by L. monocytogenes .
This prevention is carried out through good agricultural, industrial and household hygiene practices, for example:
– refrigerated food storage set at + 4 ° C;
– clean the food properly;
– respect the rules of domestic hygiene (cleaning utensils and work surfaces, etc.);
– wash your hands thoroughly after handling raw consumables;
– keep the leftovers in the refrigerator within less than 3 days;
– respect the deadlines for consumption;
It is advisable for people at risk to avoid eating deli meats (rillettes, pâté, foie gras, etc.), raw milk products, smoked fish, raw shellfish, etc.