[Overview of Listeria monocytogenes infection].

Listeriosis is an uncommon but potentially serious infection caused by Listeria monocytogenes. The main route of transmission is through the consumption of contaminated food. It generally affects elderly people, pregnant women and immunosuppressed hosts, although cases are also seen in immunocompetent adults and children. Listeria monocytogenes is a short, anaerobic, non-spore-forming gram-positive bacillus that causes a narrow zone of hemolysis in blood agar. It is a facultative intracellular pathogen, and therefore it shows a complex pathogenesis. This bacterium has the ability to cross the intestinal barrier, the placenta and the blood-brain barrier producing gastroenteritis, maternal-fetal infections and meningoencephalitis. It is most commonly diagnosed from a positive culture of a sterile site. The treatment of choice includes the use of intravenous ampicillin alone or in combination with gentamicin.