Food Safety, Preparation and Storage Tips
Cooperative Extension, College of Agriculture & Life Sciences, the University of Arizona


Listeria is a food-borne illness caused by bacteria that is able to grow in the refrigerator. In recent years outbreaks have been linked to contaminated coleslaw, milk, and cheese. Listeria is caused by bacteria found in soil, water and plant matter. Listeria can be present in raw milk and soft cheese products or raw vegetables. Poultry, meats like hot dogs and lunch meat and prepared, ready-to eat foods may also have the bacteria.

Flu-like symptoms, including nausea, vomiting, diarrhea, headache, chills and fever in otherwise healthy adults generally begin 2 to 3 days after contaminated food is eaten. In newborn infants, it can cause meningitis which is an inflammation of the brain and spinal cord, severe retardation and even death. The elderly and those who are already ill or who have lowered immunity are also at high risk after eating food contaminated by listeria.

Fortunately, poisoning from Listeria and most food-borne illness CAN be prevented.

  • Do not buy dairy products that are raw or say unpasteurized.
  • Wash or peel raw vegetables.
  • Cook meat and poultry thoroughly or until juices are clear, not pink or red. Proper cooking will kill the bacteria.
  • Refrigerate leftovers in shallow containers right after eating.
  • When microwaving, follow the owner's manual and rotate food to make sure it is cooked thoroughly and evenly.
  • When reheating leftover food or cooking ready-to-eat refrigerated foods or hot dogs, cook until steaming hot. Make sure to bring "wet" foods like sauces, gravies and soups to a full boil.
  • Pregnant women and other high risk groups are advised to carefully observe "keep refrigerated", "sell by", and "use by" dates on processed products.
  • Wash your hands, knives, cutting boards and counters with soap and water after contact with raw meat or poultry.
  • Never allow raw meat juices to mix with food that will not be cooked.

Food processors also have a responsibility in preventing Listeria through careful monitoring procedures. Prevention is the responsibility of food processors as well as consumers.

Listeria can be prevented by following these guidelines:

  • Don't buy unpasteurized milk or dairy products.
  • Wash or peel raw vegetables.
  • Cook meat and poultry until well done.
  • Reheat leftovers until steaming hot.
  • Carefully follow "keep refrigerated", "sell by" and "use by" dates.
  • Wash hands and preparation areas often when handling food.

Remember, you can control food-borne illness by proper cooking and handling techniques.


Material written by Mary Abgrall and Scottie Misner, June 1998.
Part of Food Safety Tips, College of Agriculture, The University of Arizona
Document located at
Return to Food Safety Tips listing
Return to College of Agriculture publications list