Listeria monocytogenes

Listeria monocytogenes is a species of Gram-positive, rod-shaped bacterium that can cause the foodborne disease listeriosis. It is facultatively anaerobic, meaning it can grow with or without oxygen, and occurs widely in environments such as soil, water, and decaying vegetation. Human infection most commonly follows consumption of food contaminated with the bacterium .¹

An important feature of L. monocytogenes is its ability to survive and grow at low temperatures, including refrigeration temperatures. This distinguishes it from many other foodborne bacterial pathogens whose growth is more strongly restricted by refrigeration. Its ability to tolerate environmental stresses and persist in food-production environments makes control of contamination particularly important for refrigerated, ready-to-eat foods .^1,2

L. monocytogenes is also a facultative intracellular pathogen, meaning it can invade and reproduce inside host cells. After entering a cell, the bacterium can escape from the membrane-bound compartment that initially contains it and multiply in the cytoplasm. It can then use the host cell's actin cytoskeleton to move within the cell and spread directly into neighboring cells. This intracellular lifestyle is an important part of its ability to cause invasive disease .³

Infection with L. monocytogenes is called listeriosis. Some infections cause a self-limited gastrointestinal illness, while invasive listeriosis occurs when the bacterium spreads beyond the intestine. Invasive disease is particularly important during pregnancy and in newborns, older adults, and people with weakened immune systems .¹