Listeria is a genus of 28 identified bacterial species, named after the pioneer of sterile surgery Joseph Lister, which acts as an intracellular parasite in mammals. Its most significant member, Listeria monocytogenes, is a major human pathogen uniquely capable of growing at refrigerator temperatures (as low as 4°C), commonly contaminating uncooked and ready-to-eat foods. This bacterium causes listeriosis, a relatively rare but potentially lethal foodborne illness first documented in humans in 1929, with a high case-fatality rate of 20–30% in severe cases.
Listeriosis poses a serious threat to vulnerable populations, including pregnant women, newborns, the elderly, and individuals with weakened immune systems, often leading to severe infections like sepsis and meningitis. While pasteurization and thorough cooking effectively kill Listeria, contamination can occur after processing, highlighting the critical need for strict sanitation in food preparation to prevent outbreaks.