Storing food in the refrigerator does not completely stop bacteria growth. Listeria can grow on foods even when they are refrigerated.
Listeria can cause a life-threatening infection called Listeriosis. Highly susceptible populations, such as pregnant women and their newborns, adults 65 and older, and others with weakened immune systems are the most likely to catch the disease.
In order to keep your food safe, always mark open or leftover foods with a use-by date no longer than seven days after it was opened or prepared.