Which bacterium causes the foodborne illness listeriosis and can grow at refrigerator temperatures?

Listeria monocytogenes causes listeriosis and can grow at refrigerator temperatures.

This Gram-positive bacterium is widespread in soil, water, animals, and food-processing environments. Unlike many foodborne pathogens, it can multiply at ordinary refrigeration temperatures, although cold slows its growth. This property makes ready-to-eat refrigerated foods an important public-health concern.

Listeriosis is often mild in healthy adults, but it can become severe in pregnant people, newborns, older adults, and people with weakened immune systems. Infection during pregnancy can cause miscarriage, stillbirth, or serious illness in a newborn.

L. monocytogenes is also notable for its ability to move inside host cells. It uses a protein called ActA to trigger polymerization of host-cell actin, helping it travel from cell to cell. The organism is named after Joseph Lister, whose work influenced antiseptic surgery.