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Listeriosis: What is it, Symptoms and How to Treat It

Updated in October 2019

Listeriosis is an infectious disease caused by the bacteria Listeria monocytogenes, which can be found in soil, mud and water, and can be transmitted through the consumption of contaminated food and water, such as unpasteurized milk, cheeses, vegetables, seafood and sausage.

The infection can often be asymptomatic, however the symptoms may appear in children, pregnant women, the elderly and patients with chronic diseases, since the immune system is compromised. The initial symptoms of listeriosis can be confused with those of the flu, since there is fever, body aches and chills, for example, however it is common that there are pains in the body and diarrhea, for example.

To avoid this bacteria, it is important to always wash your hands and food before consuming it. In addition, whenever there is confirmation of listeriosis, notify the health surveillance so that the cause of the infection can be investigated.

Listeriosis: What is it, Symptoms and How to Treat It

Listeriosis symptoms

Listeria monocytogenes has a variable incubation time, for example the time between contact with the bacteria and the appearance of the first symptoms can vary between 3 and 60 days. Symptoms vary depending on the infected person, with symptoms being most severe when your immune system is most debilitated. The main symptoms of listeriosis are:

  • Muscle aches;
  • High fever, greater than 38ºC;
  • Vomiting;
  • Chills;
  • Headache;
  • Loss of appetite;
  • Diarrhea;
  • Mental confusion;
  • Fatigue.

In more serious and rare cases, Listeria monocytogenes can spread into the bloodstream and reach the nervous system, causing meningitis, which is an inflammation in the membranes that surround the brain. In addition, if pregnant women become infected it can be serious and result in the death of the baby, premature birth or infection at the time of delivery.

How transmission occurs

Listeria monocytogenes can be found in various foods because of their ability to survive at different temperatures and environmental conditions, especially lower temperatures, and huge pH variations. Therefore, it is able to survive the whole system of food processing and handling.

Transmission of this infectious agent occurs mainly from the consumption of contaminated foods and water, such as unpasteurized milk, dairy products, fruit, vegetables, legumes, meats, fish, smoked and frozen seafood, and sausages.

Although these foods may contain the bacteria, it does not mean that they always have this infectious agent and that even when eating the food, the person will be infected and will have symptoms. The bacteria can also be found in soil, water and vegetation, and so it is important to wash your hands and food before eating.

Listeriosis: What is it, Symptoms and How to Treat It

How is the diagnosis reached

The diagnosis of listeriosis is done in the laboratory, where the microorganism is isolated. The bacteria can be isolated from various biological materials, such as blood, liquor, amniotic fluid, placenta, gastric lavage, or stools, depending on the symptoms and physician's indication.

What is the treatment for listeriosis

The treatment of listeriosis is done with the use of antibiotics, and the doctor usually recommends the use of Penicillin or Ampicillin associated with Aminoglycosides, such as Gentamicin. If you are allergic to Penicillin, the alternative is to use of Sulfamethoxazole-Trimethoprim, known as Bactrim.

How to prevent and avoid listeriosis

To avoid contamination by Listeria, it is important to follow some hygiene measures, such as:

  • Washing your hands before meals;
  • Washing your foods, like fruits, vegetables before eating them;
  • Storing food properly;
  • Keeping the refrigerator clean;
  • Avoiding the consumption of processed and unpasteurized foods.

In the USA there is about 1600 cases of Listeriosis a year and in the UK about 200 cases. It is important that as the first symptoms appear and listeriosis is confirmed, it is recommended you inform health surveillance so that effective preventive measures are implemented, such as banning educational products and programs.


  • AUTORIDADE DE SEGURANÇA ALIMENTAR E ECONÔMICA. Listeria. Link: <www.asae.gov.pt>. Access in 15 Jul 2019
  • SECRETARIA DE ESTADO DA SAÚDE DE SÃO PAULO. Doenças transmitidas por água e alimentos - Listeria monocytogenes. 2013. Link: <www.saude.sp.gov.br>. Access in 15 Jul 2019
  • DE SOUZA, Ana Paula O.; ARAUJO, Guilherme M. B.; FERREIRA, Maria José. Listeriose na gravidez. Rev Méd Minas Gerais. Vol 20. 432-434, 2010
  • DIREÇÃO GERAL DE SAÚDE. Listeriose. Link: <www.dgs.pt>. Access in 15 Jul 2019
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