Listeriosis is a serious food infection caused by the bacterium Listeria monocytogenes. It has been demonstrated that this pathology is particularly dangerous during pregnancy.


Human Listeriosis is one of the most important causes of death for food-borne infections in industrialized countries. In 2014 alone, 2.161 cases of Listeriosis were confirmed in Europe, causing 210 deaths (rate of mortality = 15%), a value that overcomes that of other nutritional pathologic agents such as Salmonella Spp. and it is close to the one of Clostridium botulinum. Moreover, the probability to incur in the infection with nutrients is three times higher for the elderly (70 y/o and over), and 20 times higher for pregnant women and people with diseases of the immunitary defenses.


In immunocompetent patients, Listeriosis can manifest itself with a relatively benign gastroenteritis form, with abdominal pain, diarrhea, fever, and hallucinations. Incubation is mostly short (12 to 48 hours) and the clinical progress usually runs out in a few days. The incubation period may reach up to 70-90 days in cases of abortion and stillbirth. Because of its high invasiveness, unusual for other types of bacterial infections, Listeria monocytogenes can also overcome the Blood–brain barrier and the placenta; in the latter case, the infection may spread to the fetus, by inducing intrauterine death, abortion, or severe fetal malformations.

Why is the diagnosis so important during pregnancy?

In the expectant women Listeriosis can cause fever, muscle pain, malaise and lumbar pain sometimes accompanied by diarrhea, nausea, and vomit; for the fetus, it can cause premature birth, intrauterine fetal death or early infection. The Listeriosis can be transmitted to the fetus through the placenta even if the mother does not show any symptoms; therefore, it is possible that an apparently unexpected abortion may have been caused by a non-diagnosed Listeria monocytogenes infection. It is important to stress that an early administered antibiotic therapy can prevent the transmission of the infection from the pregnant woman to the fetus.

When to do the test?

According to the information published by the Italian Istituto Superiore di Sanità, as a consequence of the potential risk of the Listeriosis for the fetus, it is recommended to evaluate any possible fever events during gestation. In particular, the test is suggested in the following cases:

  • For preventive purposes, the test should be done by every pregnant woman and, due to the fact that Listeriosis could have no symptoms, it should be repeated every three months.
  • For women who already had an abortion
  • For women that already had a premature birth
  • For pregnant women with symptoms like fever, headache, myalgia, gastrointestinal symptoms
  • For patients with recurrent spontaneous abortions

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