What is "listeria"

n. Any rod-shaped, gram-positive bacterium, of the genus ''Listeria'', especially those responsible for listeriosis

n. any species of the genus Listeria

Listeria is a genus of bacteria that up to 1992 contained 10 known species, each containing two subspecies. As of 2014, another five species were identified. Named after the British pioneer of sterile surgery Joseph Lister, the genus received its current name in 1940. Listeria species are gram-positive, rod-shaped, and facultatively anaerobic, and do not produce endospores. The major human pathogen in the Listeria genus is L. monocytogenes. It is usually the causative agent of the relatively rare bacterial disease listeriosis, a serious infection caused by eating food contaminated with the bacteria. The disease affects pregnant women, newborns, adults with weakened immune systems, and the elderly.

Listeriosis is a serious disease for humans; the overt form of the disease has a case-fatality rate around 20%. The two main clinical manifestations are sepsis and meningitis. Meningitis is often complicated by encephalitis, when it is known as meningoencephalitis, a pathology that is unusual for bacterial infections. L. ivanovii is a pathogen of mammals, specifically ruminants, and has rarely caused listeriosis in humans. The incubation period can vary between 3 and 70 days.