The bacteria of the genus Listeria are gram-positive, non-spore forming, mobile rods. Among seven Listeria species, Listeria monocytogenes is the most common human pathogenic species. Because the bacteria require only few nutrients, they exist for a relatively long time at temperatures between -0.4°C and +45°C. The pathogen occurs in animals and humans. It can survive both inside and outside organisms, and reproduces intracellularly.
Worldwide, Listeria monocytogenes can be found in the environment (for example, in compost, waste water, earth or plants) and in agriculture. The pathogen is often detected in animal feed in particular, but also in animal faeces, and in the stool of healthy people. Raw milk, raw meat, meat products, milk, dairy products (especially cheese) and salads can become contaminated during processing.
The pathogen is mainly transmitted through consumption of contaminated food of animal and vegetable origin. A faecal-oral spread through excrements from healthy people or animals is also possible. Another risk of infection is direct contact with infected humans, animals or soil. The incubation period for gastrointestinal symptoms is a few hours to six days; other disease courses have an incubation period of 1 to 14 days.
In pregnancy-associated cases, the literature indicates an incubation period of 17 to 67 days. Especially during pregnancy, the consumption of raw meat and fish, as well as cheese from raw milk should be avoided, as these foods may be contaminated.
For most people with an intact immune system, the course of the disease is asymptomatic. In some cases, patients may experience a slight feeling of illness and fever. People with a weakened immune system may experience severe flu-like conditions. Listeriosis is treated with antibiotics. The therapy should continue at least 14 days to prevent a relapse.
If listeriosis occurs during pregnancy, there is a risk that the unborn child will be born infected, which can have serious consequences. In some cases, it can lead to premature and stillborn births, or to a neonatal listeriosis. In such circumstances, newborns can develop a purulent and sometimes fatal meningitis.
There is an obligation to report diagnosed listeriosis. A vaccination against listeriosis is not yet available. Standard hygiene measures are sufficient for the treatment and care of listeriosis patients; special measures such as isolation are not required. An exception may be a woman who has just given birth to a child suffering from listeriosis.
One day to several months
The necessary spectrum of activity against Listeria monocytogenes is: bactericidal