Listeria monocytogenes

Characteristics
Morphology	Listeria monocytogenes is a facultative anaerobic, gram-positive, rod-shaped coccobacillus, typically measuring 0.5 to 2μm long and 0.5μm in diameter. L. monocytogenes is divided into 11 serovars; however, most human and animal cases are caused by serovars 4b, 1/2b, and 1/2a.
Growth Conditions	L. monocytogenes has the ability to grow at low temperature, a range of pH values (between 4.3 and 9.6), and can reproduce at temperatures between 1 and 45°C (usually in Tryptic Soy Broth).

Health Hazards
Host Range	Humans and other mammals, fish, crustaceans, and insects
Modes of Transmission	The predominant mode of L. monocytogenes transmission is by ingestion of contaminated food and leads to listeriosis. L. monocytogenes can also be transmitted transplacentally from mother to child during pregnancy and via the birth canal during birth. Nosocomial infections and person-to-person transmission (excluding vertical) are recognized but rare.
Signs and Symptoms	Symptoms of listeriosis include fever, muscle ache, nausea, and diarrhea may occur. Infection may spread to the nervous system causing meningitis. Endocarditis (inflammation of the heart’s inner lining), septicemia, and disseminated granulomatous may occur in infected adults. Pregnant women may experience only a mild, flu-like illness. However, infections during pregnancy can lead to abortion, stillbirth, premature delivery, or infection of the newborn.
Infectious Dose	Unknown
Incubation Period	Can vary depending on the mode of transmission and dose received, but typically ranges from 1 to 4 weeks, and can be as high as several months

Medical Precautions/Treatment
Prophylaxis	None publically available, but risk can be reduced through avoidance of raw food and vegetables, undercooked meat, and cheeses prepared from unpasteurized milk
Vaccines	None publically available
Treatment	Antibiotic treatment is available
Surveillance	Monitor for symptoms. Listeriosis can be diagnosed in the laboratory by cultivation of the organism, and demonstration of the infectious agent or its products in tissues or body fluids.
GWU Requirements	Report all incidents to the Office of Risk Management as well as the Office of Research Safety (ORS) IMMEDIATELY FOLLOWING THE OCCURRENCE.

Containment
BSL-2	Risk Group 2 classification is applied to L. monocytogenes. BSL-2 practices, containment equipment, and facilities are recommended when working with clinical specimens and cultures known or suspected to contain Listeria. Due to potential risks to the fetus, it is recommended that pregnant women be advised of the risk of exposure to L. monocytogenes.
ABSL-2	ABSL-2 practices, containment equipment, and facilities are recommended for activities involving experimentally or naturally infected animals.

Spill Procedures
Small Spills (<1 liter)	If the spill occurred inside a biological safety cabinet, close the sash and allow the cabinet to operate for 15 minutes before continuing with the spill cleanup. L. monocytogenes is not commonly transmitted via aerosols, but caution should be taken during a spill outside of a BSC. Leave the room immediately and allow the aerosols to dissipate for 15 minutes. Notify others working in the lab. Don appropriate PPE. Cover area of the spill with paper towels or any absorbent material and apply an EPA registered disinfectant effective against the bacteria (bleach, ethanol, glutaraldehyde), working from the perimeter towards the center. Allow 30 minutes of contact time before disposal and cleanup of spill materials.
Large Spills	Alert lab personnel in the laboratory to the spill and keep people out of the area to prevent spread of the contamination. Check if you have been contaminated or if any of your PPE has been breached. If so follow exposure procedures. Remove any contaminated clothing and place it the biohazard waste. Wash your hands and post a sign on the door. Notify your supervisor of the incident and call ORS (4-8258) for assistance. If the situation involves an imminently life-threatening injury or has catastrophic potential, call 911.

Spill Procedures

Small Spills (<1 liter)

If the spill occurred inside a biological safety cabinet, close the sash and allow the cabinet to operate for 15 minutes before continuing with the spill cleanup.

L. monocytogenes is not commonly transmitted via aerosols, but caution should be taken during a spill outside of a BSC. Leave the room immediately and allow the aerosols to dissipate for 15 minutes. Notify others working in the lab. Don appropriate PPE. Cover area of the spill with paper towels or any absorbent material and apply an EPA registered disinfectant effective against the bacteria (bleach, ethanol, glutaraldehyde), working from the perimeter towards the center. Allow 30 minutes of contact time before disposal and cleanup of spill materials.

Large Spills

Alert lab personnel in the laboratory to the spill and keep people out of the area to prevent spread of the contamination. Check if you have been contaminated or if any of your PPE has been breached. If so follow exposure procedures. Remove any contaminated clothing and place it the biohazard waste. Wash your hands and post a sign on the door. Notify your supervisor of the incident and call ORS (4-8258) for assistance. If the situation involves an imminently life-threatening injury or has catastrophic potential, call 911.

Exposure Procedures
Mucus Membrane	Flush eyes, mouth or nose for 15 minutes at eyewash station.
Other Exposure	For an area not protected by skin, wash with soap and water for 15 minutes (open wounds, sores, etc.)
Reporting	Report ALL injuries to the PI immediately and reported to the Office of Risk Management at [email protected] IMMEDIATELY FOLLOWING THE OCCURRENCE. Exposures that involve a bloodborne-pathogen or recombinant DNA also need to be reported to the Office of Research Safety at [email protected]. If the injury requires immediate medical attention, call GWPD at 202-994-6111 or call 911.
Medical Monitoring	Seek immediate medical evaluation, treatment, and post exposure follow-up at the Employee Health Office at GWU Hospital (900 23rd St., NW, Suite G-1090, Phone: 202-715-4275). Students should go to the Students Health Office at Marvin Center. After hours treatment can be received at the GWU hospital emergency room.

Stability
Disinfection	Susceptible to 1% sodium hypochlorite, 70% ethanol, 2% glutaraldehyde. Five to 10-fold higher concentrations of the above compounds are required at 4°C temperatures.
Inactivation	L. monocytogenes can be inactivated by ozone, high pressure (500MPa), and high temperatures (at least 70°C for 2 minutes)
Survival Outside Host	L. monocytogenes is commonly found in nature, particularly in association with soil, is relatively heat resistant, can tolerate cold temperature environments well, and can survive at low pH

Personal Protective Equipment (PPE)
Minimum PPE Requirements	At minimum, personnel are required to don gloves, closed toed shoes, lab coat, and appropriate face and eye protection prior to working with L. monocytogenes. Additional PPE may be required depending on lab specific SOPs. Higher containment levels will require donning scrubs and wearing respiratory protection.
Additional Precautions	Additional protection may be worn over laboratory clothing when infectious materials are directly handled, such as solid-front gowns with tight fitting wrists, gloves, and respiratory protection. Wash hands with soap and water after removing gloves.

References
CDC (https://www.cdc.gov/listeria/) BMBL 6th Edition (https://www.cdc.gov/labs/BMBL.html) Canadian PHAC (https://www.canada.ca/en/public-health/services/laboratory-biosafety-bi…) Growth Limits of Listeria monocytogenes (https://journals.asm.org/doi/10.1128/AEM.66.11.4979-4987.2000)