Listeriosis: A bacterial infection preventable with proper food hygiene

Listeriosis is an infection caused by the bacterium Listeria monocytogenes, a highly resistant microorganism. This characteristic allows it to survive and multiply in unusual conditions, such as low temperatures and humid or salty environments. Due to these properties, Listeria monocytogenes is found in soil, water, and can contaminate various foods, posing a public health risk.
Learn more about listeriosis: how you can get infected, what the specific symptoms are, who is most at risk, and most importantly, how you can protect yourself!

Listeriosis: what causes it and how is it transmitted?

Listeria monocytogenes is a ubiquitous bacterium found in various environments, including soil, water, vegetation, and the intestinal tract of animals. Its ability to survive under refrigeration makes it particularly dangerous, especially in processed and cold-stored foods. In this chapter, we will present the definition of listeriosis, as well as the causes and transmission mechanisms of the infection.

What is listeriosis?

Listeriosis is an infectious disease caused by a bacterium called Listeria monocytogenes. The infection manifests through a wide range of symptoms, from mild, flu-like forms to severe complications such as meningitis and septicemia.

The bacterium Listeria monocytogenes

Listeria monocytogenes can survive in both the presence and absence of oxygen, allowing it to thrive in a variety of environments, including vacuum-packed foods. The bacterium has flagella: tail-like structures that enable it to move. This mobility contributes to its ability to invade host cells and spread within the organism.

Furthermore, it is resistant to a variety of environmental conditions, including low pH, high salt concentrations, and dryness. This resistance contributes to its ability to persist in the environment and in food, making it particularly dangerous.

Overall, the incidence of listeriosis is relatively low. Hygiene measures, pasteurization, and constant education, which has made people aware of the risks associated with consuming contaminated food, make it one of the less frequently encountered diseases. However, its severity remains the same, and it is important to remember why food hygiene is so crucial.

Listeriosis in humans: modes of transmission

The primary mode of transmission of listeriosis is through the consumption of contaminated food. The bacterium can contaminate a variety of foods, including:

• unpasteurized dairy products (raw milk, soft cheeses);
• raw or undercooked meat (beef, chicken, pork, processed meats);
• raw or smoked fish;
• unwashed vegetables;
• raw seafood;
• ready-to-eat foods (salads, sandwiches) contaminated after preparation.

Listeria monocytogenes can survive and multiply at low, refrigerated temperatures. This characteristic makes it a major concern for food safety, both in the food industry and in your home kitchen.

Listeriosis: specific symptoms and signs

Listeriosis symptoms vary depending on the severity of the infection and the overall health status of the infected person. There are two main forms of this disease: invasive and non-invasive. The invasive form is more serious, as the bacterium does not stop at the digestive system but spreads throughout the body, affecting vital organs such as the brain and nervous system. Without prompt treatment, invasive listeriosis can be fatal, while the non-invasive variant most often resolves on its own without medical treatment.

In its non-invasive form, listeriosis symptoms are mild:

• fever;
• chills;
• muscle aches;
• headaches;
• nausea;
• vomiting;
• diarrhea.

These usually appear a few days after consuming contaminated food and can be mistaken for a simple flu.

In its invasive form, symptoms become severe:

• high fever;
• stiff neck;
• confusion;
• seizures;
• loss of balance;
• septicemia (generalized blood infection);
• meningitis (inflammation of the membranes surrounding the brain and spinal cord).

These symptoms usually appear a few weeks after the initial infection and require hospitalization and emergency treatment.

Certain individuals are at increased risk of contracting the infection

Although anyone can be infected with Listeria monocytogenes, certain individuals are more susceptible to developing severe forms of listeriosis:

• pregnant women;
• newborns;
• elderly individuals (over 65 years old);
• people with weakened immune systems (people with HIV/AIDS, cancer, diabetes, organ transplant recipients);
• people undergoing immunosuppressive treatments.

For these individuals, preventive measures and careful monitoring of any apparent “cold” are extremely important.

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Young children, pregnant women, and individuals with weakened immune systems should always consult a doctor before introducing a new dietary supplement into their diet. While supplements can support the immune system and provide essential nutrients, it is important that they are chosen carefully and are safe for vulnerable groups.

Listeriosis in pregnancy: characteristic complications

Although it may go unnoticed, untreated listeriosis, especially when present in vulnerable groups, can lead to serious complications:

• systemic infections;
• septicemia;
• encephalitis, meningitis or abscesses;
• permanent neurological sequelae;
• infertility.

All of these can, in principle, be prevented through rigorous food hygiene.

Listeriosis and pregnancy

Listeriosis during pregnancy can have serious consequences for both the mother and the fetus. Infection with Listeria monocytogenes during pregnancy can cause:

• miscarriage;
• premature birth;
• severe neonatal infections (septicemia, meningitis);
• fetal death.

Pregnant women must be particularly careful in observing food hygiene rules and avoid consuming foods with a high risk of Listeria contamination.

Furthermore, newborns can become infected with Listeria monocytogenes during birth if the mother is infected. In infants, symptoms include fever, vomiting, incessant crying, difficulty breathing, and refusal to eat. Such an infection is serious, requiring emergency treatment, usually with antibiotics.

Listeriosis disease: diagnosis and prevention

Diagnosing listeriosis is essential for initiating prompt treatment and preventing severe complications. It is established based on clinical symptoms and laboratory tests.

Since listeriosis symptoms can be non-specific and easily confused with other conditions, laboratory tests are essential and include:

• Bacterial cultures from blood, cerebrospinal fluid (in case of meningitis), or amniotic fluid (in pregnant women); after birth, biological samples can be collected from the placenta, in case of suspected infection in newborns;

Samples are cultured on special culture media, and the growth of Listeria monocytogenes confirms the diagnosis. The bacterium is identified through biochemical and serological tests.

• Serological tests detect antibodies produced by the body in response to Listeria monocytogenes infection. They can be useful in determining if someone has had a recent infection with Listeria, but they are not always conclusive, as antibodies can persist in the blood long after the infection has cleared.
• Molecular biology tests (PCR) detect the genetic material of the bacterium (DNA) in biological samples. PCR is a rapid and sensitive diagnostic method, particularly useful in severe cases where quick confirmation of the diagnosis is needed.

Importance of correct diagnosis and treatment of infection

Early diagnosis allows for the rapid initiation of antibiotic treatment, which reduces the risk of severe complications and mortality. Furthermore, rapid identification of the infection allows for close monitoring of patients and prompt intervention in case of complications such as meningitis or septicemia. Last but not least, the diagnosis of listeriosis allows public health authorities to identify the source of the infection and take measures to prevent its spread.

Regarding the **treatment** of listeriosis, it consists of administering antibiotics. In severe cases, hospitalization or intravenous administration of antibiotics may be necessary.

Food safety measures and personal hygiene

Prevention of listeriosis is primarily based on observing simple food hygiene rules:

• wash your hands thoroughly with soap and water before preparing food and after handling raw meat;
• wash fruits and vegetables thoroughly before consumption;
• cook meat to the recommended internal temperature;
• keep raw foods separate from cooked foods;
• refrigerate perishable foods at temperatures below 4°C;
• consume perishable foods as quickly as possible;
• avoid consuming unpasteurized dairy products;
• pay attention to food expiration dates;
• regularly clean and disinfect work surfaces, kitchen utensils, and equipment.

By following these simple but important measures, you can significantly reduce the risk of Listeria infection and protect your health and that of your loved ones.

Stay informed about food alerts and product recalls. As with any foodborne illness, listeriosis can be prevented with rigorous hygiene. If you detect specific symptoms and suspect consumption of certain foods as the cause, consult your doctor immediately.

In conclusion, listeriosis is a dangerous infection. Its prevention is very important and is achieved by following food hygiene and proper product storage measures. Awareness of risks and education on food safety are essential for protecting health, especially for vulnerable groups.

Take care of your health and the health of those around you!

References:

https://www.who.int/news-room/fact-sheets/detail/listeriosis

https://www.cdc.gov/listeria/about/index.html

https://my.clevelandclinic.org/health/diseases/17721-listeriosis

https://www.nhs.uk/conditions/listeriosis/