It is recommended they be heated to steaming first. Listeria monocytogenes is a type of bacteria that is found in water and soil. Vegetables can become contaminated from the soil, and animals can also be carriers. Listeria has been found in uncooked meats, uncooked vegetables, unpasteurized milk, foods made from unpasteurized milk, and processed foods. Listeria is killed by pasteurization and cooking. There is a chance that contamination may occur in READY-TO-EAT foods such as hot dogs and deli meats because contamination may occur after cooking and before packaging.