Listeria – Expert Fact Sheet

In this document, Food Safety Expert, Barry E. Parsons, FMP, CP-FS, CCFS provides introductory information on Listeria, including symptoms, notable outbreaks, and what food service establishments should be doing to prevent outbreaks.


Approximately 1,600 illnesses and 260 deaths are attributed to listeriosis, from Listeria Monocytogenes (LM), in the United States each year. A large outbreak linked to cantaloupes occurred in the United States in 2011, causing 147 illnesses, 33 deaths, and 1 miscarriage (CDC, 2015).


Food products commonly associated with Listeria bacteria include:

  • Hot dogs
  • Luncheon meats
  • Smoked seafood
  • Soft cheeses
  • Meats & poultry
  • Vegetables & fruits


Symptoms of Listeriosis include:

  • Fever
  • Stiff neck
  • Weakness
  • Vomiting
  • Confusion

Source: Listeria, 2015

In invasive listeriosis, the elderly, persons with weakened immune systems and unborn children (exposed after the mother is infected with LM) have a higher risk of death.


Food service establishments must have effective sanitation and personal hygiene programs. Drains should be an area of focus, particularly floor and condensate drains. Cleaning with the proper chemicals is important as LM can form biofilms that act as protective barriers (PSU, 2006). Spray sanitizer alone is not effective on biofilms.

Listeria Monocytogenes (LM) is ubiquitous, it can be found in the air, soil, water, and fecal material. LM is robust, it can grow in refrigerated temperatures (Psychrophilic) and survive freezing temperatures (PSU, 2006).

Retailers and processors should emphasize personal hygiene and eliminate pests to control cross-contamination. They should also clean air vents and follow validated Standard Sanitation Operating Procedures for refrigeration cases, slicers, meat saws, cutting boards and any other equipment that comes into contact with food

Investigatory Questions:

  1. Have food safety plans been validated: Why are identified hazards significant? Are control measures effective? What is the basis for critical limits?
  2. Have food safety plans been verified: Are control measures, testing, and monitoring working as intended? Are plans being carried out properly?

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