What Is Listeria?
Medically reviewed by Jane Kim, MD
Listeria is a type of bacterial infection that causes foodborne illness. It can lead to a range of symptoms, from mild flu-like symptoms to severe complications, especially in vulnerable populations like pregnant women, newborns, older adults, and people with weakened immune systems. About 1,600 people get listeriosis each year and about 260 die from this foodborne illness.
Eating contaminated foods is the most common way people get Listeria. Left untreated, this infection can lead to serious complications. Fortunately, there are several treatment options and prevention measures you can take against Listeria.
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Listeria Symptoms
Listeria can manifest with a range of symptoms that can vary in severity, which may include:
Muscle aches
Diarrhea
Headache
Stiff neck
Confusion or changes in alertness
Loss of balance
Convulsions
The severity of symptoms can vary widely depending on individual factors like age, overall health, and immune status. People who are pregnant may experience symptoms such as fever and flu-like symptoms, but the infection can also lead to miscarriage, stillbirth, premature delivery, or life-threatening infection of the newborn.
Older adults and individuals with weakened immune systems may experience more severe symptoms and complications. If you suspect you or someone you know may have listeriosis, it's crucial to contact your healthcare provider right away.
What Causes Listeria?
Listeria is primarily caused by the bacterium Listeria monocytogenes (L. monocytogenes), commonly found in soil, water, and some animals. It's a type of bacteria capable of surviving and even thriving in various environments, including those with low temperatures, such as a refrigerator.
Humans are typically exposed to L. monocytogenes by consuming food products contaminated with the bacterium. These foods typically include:
Unpasteurized dairy products
Contaminated vegetables
Raw or processed (e.g., pre-peeled or pre-sliced) fruits
Processed meats
The longer foods contaminated with L. monocytogenes are stored in the refrigerator, the more time the pathogen has to grow. Unlike other types of bacteria, L. monocytogenes can grow at refrigerated and freezing temperatures.
Risk Factors
Several factors can increase the susceptibility of Listeria infection, including:
Pregnancy
Older age
Weakened immune system due to conditions such as HIV/AIDS or cancer
Certain medical treatments like chemotherapy or organ transplantation
Consumption of contaminated foods, particularly those listed above
Pregnant individuals are at heightened risk due to changes in their immune system, making them more susceptible to Listeria infections. This can have severe consequences for both the pregnant person and the fetus. Pregnant people are 10 times more likely than others to get a Listeria infection.
How Is Listeria Diagnosed?
If you are experiencing Listeria symptoms and you suspect you may have been exposed to contaminated food, you should visit your healthcare provider for an evaluation. The provider will ask about your symptoms, medical history, and potential exposure to risk factors associated with Listeria infection.
From there, your provider can diagnose a Listeria infection through various laboratory tests aimed at detecting the presence of L. monocytogenes in bodily fluids or tissues. This may require a sample of blood, cerebrospinal fluid, or amniotic fluid.
Treatments for Listeria
Many people recover from intestinal Listeria without needing antibiotic treatment. However, if you have intestinal Listeria and are experiencing diarrhea, it's important to drink plenty of fluids to prevent dehydration.
Treatment for more invasive listeriosis that spreads beyond the intestines typically involves antibiotics. The choice of antibiotics depends on factors such as the severity of the infection, the person's age and overall health, and antibiotic susceptibility testing results. Commonly used antibiotics for treating listeriosis include:
Zosyn (penicillin)
Omnipen (ampicillin)
Moxatag (amoxicillin)
Sometimes, these antibiotics are used in combination with another antibiotic, such as Gentak (gentamicin).
In cases of severe listeriosis, hospitalization may be necessary for intravenous antibiotics and supportive care. Pregnant individuals diagnosed with listeriosis may also require hospitalization for close monitoring and administration of antibiotics to prevent complications for both themselves and the fetus.
How To Prevent Listeria
You can't always avoid contracting a Listeria infection. However, there are preventive measures you can take to minimize the risk of listeriosis.
Practice Safe Food Handling
Safe food handling practices include:
Thoroughly cook raw meat, poultry, and seafood to safe internal temperatures
Wash raw fruits and vegetables before consuming, and avoid cross-contamination by keeping them separate from raw meats
Promptly refrigerate perishable foods, such as leftovers, deli meats, and dairy products. and consume them within the recommended timeframes
Avoid High-Risk Foods
High-risk foods include:
Limit your consumption of unpasteurized dairy products including milk, yogurt, and soft cheeses
Limit consumption of raw or undercooked produce like melons and sprouts
Be cautious with ready-to-eat foods like deli salads (e.g., coleslaw, potato salad), deli meats, and hot dogs—ensuring they are properly heated before consumption
Avoid the above foods if you are pregnant or have a weakened immune system, or talk to your healthcare provider about what is safe to eat
Maintain Good Hygiene
Hygiene practices include:
Wash your hands thoroughly with soap and water before handling food, after handling raw meats, and after using the restroom
Keep kitchen surfaces, utensils, and cutting boards clean by washing them with hot, soapy water after each use
Only eat off of clean plates and utensils
Clean spills in the refrigerator immediately, especially if they are from meat or seafood products
Complications
Listeriosis can lead to various complications, especially in vulnerable populations such as pregnant people, newborns, older adults, and individuals with weakened immune systems. Some of the potential complications of listeriosis include:
Pregnancy complications: In pregnant individuals, listeriosis can lead to miscarriage, stillbirth, premature delivery, or life-threatening infection of the newborn. The bacterium can cross the placental barrier, causing severe infections in the fetus.
Sepsis: Listeria can enter the bloodstream and spread throughout the body, leading to sepsis. Sepsis is a severe systemic infection that can cause organ dysfunction and life-threatening complications if not promptly treated.
Meningitis: Listeria can infect the central nervous system, leading to meningitis. Meningitis is an inflammation of the membranes covering the brain and spinal cord, which can cause symptoms such as headache, stiff neck, confusion, and neurological deficits.
Brain abscess: In rarer cases, listeriosis can lead to the formation of brain abscesses, which are localized collections of pus within the brain tissue.
A Quick Review
Listeria is a serious bacterial infection that can have severe consequences, especially for pregnant women, newborns, older adults, and people with weakened immune systems. You can reduce your risk of listeriosis by practicing safe food handling and avoiding high-risk foods.
Getting an early diagnosis and appropriate treatment is crucial for managing infections and preventing complications. If you have symptoms of Listeria, contact your healthcare provider immediately.
Frequently Asked Questions
How fast does Listeria make you sick?
Listeria monocytogenes can cause symptoms of listeriosis within a few hours or days after exposure. However, in some cases, symptoms may develop as late as several weeks and up to three months after ingestion of contaminated food.
Can vinegar kill Listeria?
Distilled white vinegar (in a 5% concentration) may be effective against Listeria on food contact surfaces. However, thoroughly cooking foods destroys Listeria that may be present in food.
Is listeria the same as food poisoning?
Listeria is a bacteria that can make you sick from food, but it's not the only cause of food poisoning, which can come from different germs or toxins.
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