Food Safety

Listeria Monocytogenes

Listeria Overview for General Understanding

Listeria monocytogenes remains a food pathogen of priority due to both the severity of listeriosis in humans and the frequency of outbreaks caused by Lm contamination.

Understanding and implementing effective preventive control strategies to reduce, control and/or eliminate the risk of listeriosis in produce grown, packed, manufactured/processed or held is critical.

What is Listeria monocytogenes (Lm, or L. mono)?

  • Lm are bacteria that cause the foodborne illness Listeriosis.
  • People can get sick from Lm if they eat a food that is contaminated with Lm.
  • Foods that have been associated with Lm are raw milk, inadequately pasteurized milk, chocolate milk, cheeses (particularly soft cheeses), ice cream, raw fruits and vegetables, raw poultry and meats (all types), fermented raw-meat sausages, hot dogs and deli meats, and raw and smoked fish and other seafood.
  • Compared to other foodborne illnesses, such as Salmonella or E. coli, the number of people infected with Listeria is small. However, this bacterium is one of the leading causes of death from foodborne illness.

Who is most at risk?

  • Pregnant women are more susceptible to Listeria infection. While many pregnant women recover from the illness, their babies do not.
  • People with weakened immune systems are also more susceptible, such as AIDS and cancer patients.
  • The elderly are also especially vulnerable.

Why is Listeria monocytogenes a concern to growers, packers and fresh-cut processors?

  • Listeria can be found in the same environments where fresh fruits and vegetables are grown. It can be found in soil, water and decaying vegetation. It can also establish itself in cold, wet environments, which are common conditions in packing facilities. 
  • Listeria could possibly be transferred from raw fruits and vegetables from the field and introduced into packing facilities. This transient Listeria could become established in the facility if proper sanitation practices are not carried out. These bacteria that find a home in niches in the facility are often referred to as resident.
  • This resident Listeria could multiply if conditions are favorable in the facility and then contaminate the produce by moving from facility contact surfaces onto fruits and vegetables.
  • This cross contamination can be prevented if proper cleaning and sanitation and environmental monitoring programs are established.


What are important details about policy regarding Lm? (In the U.S. and abroad)

Industry Resources

Listeria Training

Register Now

Guidance on Environmental Monitoring and Control of Listeria for the Fresh Produce Industry (Originally developed by United Fresh)

Listeria 101 (Originally developed by PMA Australia-New Zealand)


Guidelines for Listeria Dos and Don'ts - Spanish Version (Originally developed by United Fresh)

Zone 1 Sampling for Listeria in Fresh Produce Operations (Originally developed by United Fresh)


Zone 1 Sampling Infographic (Originally developed by United Fresh)


Considerations for Fresh Produce Dry-Pack Environmental Monitoring Programs (Originally developed by United Fresh)


Strategies for Listeria Control in Tree Fruit Packinghouses (Originally developed by United Fresh)


What training is available for my organization?

New Listeria Training Workshops will be held in the coming months. Contact Alison Saltzmann for more information and to get on the wait list. 

What is the industry doing to address this issue?

Related Resources