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Listeria monocytogenes

Listeria monocytogenes

Domain : Bacteria (bacteria)
Department : Firmicutes
Class : Bacilli
Order : Bacillales
Family : Listeriaceae
Genre : Listeria
Scientific name
Pirie , 1940

Listeria (pronounced as / ⁠ ˌlɪsteːʀi̯ən ⁠ / ) are 0.4 x 1 to 1.5 microns large rod-shaped, gram positive , non Endospore-forming , facultative anaerobic bacteria of the genus Listeria, named after the British surgeon Joseph Lister . They are flagellated peritrich and can therefore move actively by swimming .


Listeria are undemanding. They can multiply in nutrient-poor substrates (puddles of water, condensation ). They achieve optimal growth in the temperature range from 30 to 37 ° C, in a pH range from 5.0 to 9.0 and a slightly increased carbon dioxide concentration . However, they can also survive and grow in the extended temperature range of 4 to 45 ° C. The fact that they are cold tolerant ( psychrotolerant ), as well as their ability to switch from aerobic metabolism to anaerobic one, allows them to reproduce in vacuum-packed foods (meat products, raw milk, cheese, smoked fish) that are in the refrigerator .

Natural occurrence

Listeria are almost ubiquitous (ubiquitous) in nature and feed on dead organic material ( saprobians ). They are found both on plant materials - for example on dead grass and in head cushion dust - as well as in the intestinal tract of humans and animals. An estimated one to ten percent of people carry Listeria in their intestines and excrete them in their stool.


Listeria can cause the notifiable infectious disease listeriosis , which is also pathogenic to humans if infected by the species Listeria monocytogenes . The latter occurs through ingestion of contaminated food, in animals (mainly cattle and sheep) through insufficiently acidified silage , in humans through the consumption of improperly produced foods (especially meat, fish and dairy products). Listeria are mainly found in unheated animal foods (for example in raw milk and in unheated raw milk cheese ). Plant-based foods are generally less affected, but listeria can get on vegetables through fertilization with animal waste water ( liquid manure ). They are also found more frequently in ready-to-cook salads.

Food safety

Although Listeria are almost everywhere, the number of detected diseases is surprisingly low (698 reports for 2018 in Germany). This could be due to the usually low content of Listeria monocytogenes in foods (less than 100 bacteria per gram), but more likely to be difficult to detect and the fact that the disease can only break out weeks later with unspecific symptoms such as fever and diarrhea. The increasing industrial production of food with its many intermediate stages increases the potential for contamination. One tries to counteract this by taking appropriate hygiene measures. Every now and then there are recalls because of Listeria. At the beginning of November 2019 z. B. Rewe and Norma recall certain meatball balls because of suspected listeria. In connection with Wilke Waldecker meat and sausage products , a German food manufacturer, three deaths were recorded in 2019. 34 diseases, including 10 deaths between 2018 and 2020, were the result of a listeria infestation in a cheese dairy in the canton of Schwyz , Switzerland.


Listeriosis is usually harmless in healthy people or is hardly noticed. If a particularly large number of pathogens are ingested, fever and diarrhea can occur. Small children or people with a weakened immune system , such as recently operated on, AIDS or cancer patients and diabetics can become seriously ill.

The onset of the disease can occur up to eight weeks after ingestion of the bacteria. Listeria can cause sepsis ("blood poisoning") or meningitis (meningitis), which can be treated with antibiotics , but still lead to death in 30 percent of cases.

Listeriosis is particularly dangerous in pregnant women, as it can have fatal consequences for the unborn child. Premature birth, severe damage, or even death of the fetus can occur. The pregnant woman, on the other hand, often does not even notice the disease.


If listeriosis is diagnosed through detection of the pathogen, the person affected is treated with antibiotics. In 70 percent of cases, the disease can be stopped in this way. Meningitis caused by Listeria monocytogenes is treated with aminopenicillins ( ampicillin or amoxicillin ), possibly in combination with aminoglycosides ( gentamicin ). The direct detection of the listeria in blood, cerebrospinal fluid or pus is not always successful. Other test methods, such as the detection of antibodies in the blood, on the other hand, are unsuitable. It follows that many diseases are not recognized at all.

Genome research

In 2001, as part of an EU-funded research project, the complete DNA base sequences of the genome of Listeria monocytogenes and Listeria innocua were determined and published, and extensive new knowledge about the biology and evolution of bacteria was derived from the comparison of the data. The DNA base sequences of the complete genome are also currently being determined for the other members of the genus Listeria .

Published genome sequences:

  • L. monocytogenes Sv1 / 2a
  • L. innocua Sv6a
  • L. monocytogenes Sv4b F2365
  • L. monocytogenes Sv4b H7858, 178 contigs
  • L. monocytogenes Sv1 / 2a F6854, 133 contigs

Identified but not yet published genome sequences:

  • L. welshimeri Sv6b
  • L. seeligeri Sv1 / 2b
  • L. monocytogenes Sv4a
  • L. monocytogenes Sv4b
  • L. ivanovii Sv5


Web links

Commons : Listeria ( Listeria )  - collection of images, videos and audio files

Individual evidence

  1. Researchers at the Technical University of Munich (TUM) have also found listeria in the mattress dust of farm children. The microorganisms may help ensure that children on the farm suffer less from allergies than children in the city. - Occurrence of Listeria spp. in mattress dust of farm children in Bavaria.
  2. High bacterial load in sprouts and ready-to-cook salad mixes . Article on (PDF file)
  3. RKI : Epidemiological Bulletin No. 3/2020 , from January 16, 2020, SS 18, for 2019: 591 cases, compared to 13,636 salmonellosis cases
  4. ^ Salmon recalled by Coop, Migros and Volg because of Listeria. In: . March 9, 2019, accessed March 11, 2019 .
  5. Listeria in meatballs: operating license is suspended. In: . November 3, 2019, accessed November 3, 2019 .
  6. 10 deaths after Listeria infestation in Schwyz - investigations against cheese dairy. Retrieved August 27, 2020 .