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Listeria monocytogenes Biological Agent Reference Sheet (BARS)

Updated November 29th, 2023

Disclaimer: Risk group, biosafety level, and all other precautions noted here are subject to change after a risk assessment by EHS.


Agent Type Risk Group Biosafety Level Animal Housing Biosafety Level
Bacteria RG-2 BSL-2 ABSL-2

Agent Characteristics 

Risk Group: RG-2 associated with human disease, rarely serious; preventive, or therapeutic interventions often available.

Agent Type: Bacteria

DescriptionListeria monocytogenes is a Gram-positive, pathogenic bacterium, in the division Firmicutes. Infection with Listeria monocytogenes can cause listeriosis. People usually become ill with listeriosis after eating contaminated food. The disease primarily affects pregnant women, newborns, older adults, and people with weakened immune systems. It is rare for people in other groups to get sick with Listeria infection. Listeriosis is usually a mild illness for pregnant women, but it causes severe disease in the fetus or newborn baby. Adults 65 years and older and people with weakened immune systems most commonly develop severe infections of the bloodstream (causing sepsis) or brain (causing meningitis or encephalitis). Listeria infections can sometimes affect other parts of the body, includiing bones, joints, and sites in the chest and abdomen.

Host Range: Humans, mammals, fish, crustaceans, insects                Host Shedding: Direct contact, feces                         

Route of Exposure to Humans: Direct contact, Vertical transmission, Ingestion, Percutaneous

Infectious Dose: Healthy hosts: 10-100 million CFU; Immunocompromised: 0.1 to 100 million CFU 

Incubation Period: Ranges from 3-70 days; median incubation period is 21 days.

Health Hazards

Signs and symptoms of infection may include:

  • Flu-like symptoms (i.e. fever, headache, dehydration, weight loss, lethargy)
  • Gastrointestinal symptoms (i.e. loss of appetite, nausea, vomiting, diarrhea)
  • Reproductive Health concerns (i.e. abortion, fetal abnormalities) 

Immunizations: None available                                          Prophylaxis*: Available

*Formal medical advice is obtained during medical consultations with Cornell Health or primary healthcare provider as needed.

Agent Viability 

Survival Outside Host Disinfection

Able to survive outside of hosts (water, soil, food,
feces); capable of growing at low temperatures (-4 to

 1:10 bleach Dilution (30 min contact time)

70% ethanol

 Inactivated by moist heat (15 minutes at
121°C), dry heat (1 hour at 160-170°C), and short
wave UV and gamma irradiation.

For more guidance on disinfection see:  disinfectant selection.

Laboratory Hazards 

  • Equipment contamination
  • Exposed skin/uncovered wounds
  • Handling of sharps (needles, scalpels, microtome blades, broken glass, etc.)
  • Splash/droplet-creating activities (shaking incubators, liquid culturing, mechanical pipetting)

Laboratory Acquired Infection (LAI) History:  Some suspected cases, none of which have been confirmed. Pregnant women should take special caution to avoid contact with infected material.

Laboratory Handling Guidelines 

Laboratory Biosafety Level (BSL): BSL-2


Lab Engineering Controls Personal Protective Equipment
  • Eye Protection
  • Single gloves
  • Snap-front lab coat with cinch cuffs

Waste Management: Regulated Medical Waste (RMW)

Shipping Guidance: Refer to EHS Biological Materials Shipping 

Animal Vivarium Guidance

Animal Housing Biosafety Level (ABSL): ABSL-2

Animal Biosecurity: Experimental animals are housed separately

Perform InoculationsBenchtop, Biosafety Cabinet, Cage Changing Station

Change CagesBenchtop, Biosafety Cabinet, Cage Changing Station

Exposure and Spill Procedures 

Mucous Membranes: Flush eyes, mouth, or nose for 15 minutes at an eyewash station. See: responding to exposures.

Other Exposures: Wash with soap and water for 15 minutes (open wounds, sores, etc.) or a minimum of 20 seconds for areas with intact skin. See: responding to exposures.

Small Spills: Notify others working in the lab. Evacuate area and allow 30 minutes for aerosols to settle. Don appropriate PPE. Cover area of the spill with paper towels and apply disinfectant, working from the perimeter toward the center. Allow 30 minutes of contact time before disposal and cleanup of spill materials. See: spill cleanup

Large Spills: Request assistance from the EHS Spill Team by calling CUPD dispatch. Call 911 from a campus phone or 607-255-1111 from a mobile phone.

Incident Reporting: Immediately report the incident to supervisor and complete the EHS online injury/illness report as soon as possible.

Medical Follow-Up:

  • For students, seek medical attention at Cornell Health or local primary care provider. Call Cornell Health at 607-255-5155 (24-hour phone consultation line) or a local urgent care. 
  • For faculty and staff, seek medical evaluation with a local primary care provider or urgent care. Cornell Health does not see employees for post-exposure care. 
  • Emergencies: Call 911 from a campus phone or 607-255-1111 from a mobile phone. 
Cornell EHS would like to thank Emory University for the use of their Biological Agent Reference Sheet (BARS) format and some content. 

More Information


  1. Biological Agent Reference Sheet (BARS). Emory University.
  2. Best M, Kennedy ME, Coates F. Efficacy of a variety of disinfectants against Listeria spp. Applied and Environmental Microbiology. 1990;56(2):377-380.
  3. Listeria (Listeriosis). Centers for Disease Control and Prevention.
  4. Listeria monocytogenes. Pathogen Safety Data Sheet. Public Health Agency of Canada.
  5. Risk Group Database. American Biological Safety Association.