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Listeriosis is an infectious disease caused by the gram-positive bacterium Listeria monocytogenes. The bacteria are usually transmitted to humans through ingestion of contaminated food especially raw milk products. In immunocompetent patients, the disease is mostly asymptomatic, although mild flu-like symptoms or febrile gastroenteritis may occur. Invasive disease due to bacteria spreading beyond the gastrointestinal tract results in most symptoms and generally develops in high-risk groups, including immunocompromised , elderly, and pregnant patients.
The clinical manifestation is usually mild in pregnant women, but consequences for the fetus can be very severe see congenital listeriosis. In immunocompromised and elderly patients, invasive disease can lead to sepsis and meningitis. Suspected listeriosis can be differentiated from other causes of infection through blood cultures. Antibiotic therapy is indicated for high-risk groups; ampicillin or penicillin G are the drugs of choice.
References:    . Listeria relies on several pathogenic mechanisms to permit infection and evasion of the host immune system :. Clearance of infection primarily relies on macrophage activation by T cells. Most infections are asymptomatic or mild , especially in immunocompetent individuals. References:   . Testing is generally not needed in immunocompetent individuals, as the infection is self-limiting and symptoms will have resolved by the time listeriosis is diagnosed.
Clinical science Listeriosis is an infectious disease caused by the gram-positive bacterium Listeria monocytogenes. Pathogen : Listeria monocytogenes ; a gram-positive , catalase-positive , rod-shaped , facultative intracellular, motile bacterium Route of transmission Contaminated food, especially raw milk products ; : Listeria can grow in temperatures as low as Listeria relies on several pathogenic mechanisms to permit infection and evasion of the host immune system : Invasion : the bacteria enter host cells via binding of the virulence factor InlA to E-cadherin in cells of the intestinal epithelium , the blood—brain barrier, and the placenta.
Proliferation : once inside the phagosome , virulence factors listeriolysin O , phospholipases enable escape from the phagosome and entry into the cytoplasm. Listeriolysin O also inactivates T cell receptors and impairs T cell activation by antigen presenting cells. Cell to cell mobility : Listeria can move from cell to cell without being exposed to the extracellular environment via actin rocket tails.
Blood cultures Indications: suspected listeriosis, particularly among high-risk groups e. In immunocompetent patients with gastroenteritis , no treatment is usually necessary. Indications for antibiotic treatment: CNS infection ; , endocarditis , bacteremia , neonatal infection , or immunocompromise First-line treatment : ampicillin or p enicillin G , usually in combination with gentamicin for synergistic effect Second-line treatment : cotrimoxazole , macrolide.
High-risk individuals : avoid food products made from unpasteurized milk and soft cheeses e. Properly cook meat prior to consumption Obligation to report : Listeriosis is a notifiable disease in the United States. Prepare and succeed on your medical exams. Find hundreds of Learning Cards covering all clinical subjects Practice answering thousands of USMLE-formatted multiple choice questions in the Qbank Explore concepts in depth with interactive images, videos and charts Fill knowledge gaps with the help of supportive features and an analysis of your progress.
Listeria monocytogenes is the species of pathogenic bacteria that causes the infection listeriosis. It is a facultative anaerobic bacterium, capable of surviving in the presence or absence of oxygen. Listeriosis mortality rates are also higher in the EU than for other foodborne pathogens. Listeria monocytogenes is a Gram-positive bacterium , in the division Firmicutes , named after Joseph Lister. See: listeriosis in animals. Due to its frequent pathogenicity , causing meningitis in newborns acquired transvaginally , pregnant mothers are often advised not to eat soft cheeses such as Brie , Camembert , feta , and queso blanco fresco , which may be contaminated with and permit growth of L. It is catalase-positive and oxidase-negative, and expresses a beta hemolysin, which causes destruction of red blood cells.