Cellulitis is a bacterial infection of the skin, usually occurring from a break in the skin, such as a cut, sore, scratch or burn. Skin affected by cellulitis quickly becomes red, swollen, hot and tender. Antibiotics may be needed to clear up the infection.…
What is listeriosis?
Listeriosis is a condition caused by Listeria monocytogenes bacteria. These bacteria are widespread in nature and can be found in the soil, water and in many animals. People most often get infected with listeria after eating food that is contaminated with the bacteria.
Listeriosis is normally a mild condition that passes after a few days and has no lasting effect. However, it can lead to complications. In pregnant women, listeriosis can lead to premature birth, miscarriage or stillbirth. In addition, a pregnant woman can transfer the bacteria to her unborn baby.
Most listeriosis cases occur as a result of eating contaminated food. Listeria monocytogenes bacteria can contaminate raw or processed food, including:
- Raw vegetables and fruit;
- Raw or smoked fish and other seafood;
- Unpasteurized milk and dairy products such as soft cheeses and butter;
- Deli meats such as ham or salami, and;
- Raw or undercooked meat.
Listeria monocytogenes bacteria are widespread in nature and are often found when testing food. They can contaminate food at any point of the food supply chain, from the soil in farms, through to all stages of food storage and processing, and in kitchens where food is prepared. Listeria are also unusual among bacteria, in that they can grow in refrigerated food.
Listeriosis often appears as outbreaks, due to an infected food source shared by multiple people. Listeriosis outbreaks occur more often in developed countries. They are rare events, appearing in 1 to 10 people per million, but severe listeriosis has a high death rate of one in five people. 
The incubation period of listeriosis, which is the time between infection and the appearance of illness, is highly variable and can be very long. Thus, it is sometimes hard to trace back the infection to its source. Many animal species also harbor the bacteria, which can then develop into listeriosis, in some animals.
Anyone can be infected with listeria, but not all people experience problems. People at risk of developing listeriosis include:
- Pregnant women;
- Elderly people, and;
- People with weak immune systems, due to illness or medication.
Listeriosis in pregnancy
In pregnant women infected with Listeria, the unborn baby can also become infected, when the bacteria move across the placenta and into the unborn baby's bloodstream. About one in five pregnant women who have listeriosis are in real danger of experiencing premature birth, birth complications, miscarriage or stillbirth.
Unborn babies and infants who contract listeriosis are at increased risk of developing complications of listeriosis, especially meningitis (see below).
Signs and symptoms
Most people who are infected with listeria will not get ill, or will experience only mild symptoms. Symptoms can resemble those of the flu and may include:
If the bacteria infect the nervous system or the blood, severe listeriosis can set in. Severe listeriosis is a serious condition and requires hospitalization.
Symptoms of severe listeriosis can include:
- Stiff neck muscles;
- Twitching and seizures;
- Loss of physical coordination, and;
Listeriosis in infants
In infants, symptoms can include:
- Loss of appetite and food refusal;
- Trouble breathing;
- Lack of energy;
- Skin rash, and;
- Upset stomach or vomiting.
Methods for diagnosis
If listeriosis is suspected, your doctor may send off tissue samples (or often blood samples) to test for the presence of Listeria.
If your doctor suspects that the bacteria may have spread to the nervous system, they may wish to sample the fluid around the spinal cord and brain, by performing a lumbar puncture. In some cases, a magnetic resonance imaging (MRI) scan of the brain is performed.
For people infected with the bacteria, who do not feel ill, further testing or treatment is usually not necessary.
Types of treatment
If treatment is necessary, your doctor will prescribe a course of antibiotic medication, such as amoxicillin or ampicillin.
Listeriosis can cause the following complications:
- Inflammation of the meninges (meningitis) and/or the brain (encephalitis);
- Blood poisoning (sepsis), and;
- Inflammation of the heart.
Complications of listeriosis can result in serious, long-lasting harm and even death, particularly among infants who develop meningitis.
In healthy older children and adults, listeriosis usually passes after a few days with no lasting harm.
The best way to prevent listeriosis is to practice good food-handling practices, including:
- Washing, scrubbing, drying and peeling fruits and vegetables;
- Handling and storing raw meat separately from vegetables and prepared food;
- Washing hands and food preparation utensils and surfaces;
- Keeping your refrigerator clean from food spills and old food;
- Paying attention to use-by dates of food products, and;
- Thoroughly cooking food, especially meat.
People at risk, such as pregnant women, may choose to avoid the risky foods listed above, including soft cheeses, unpasteurized dairy products, pâtés, deli meats, raw fish and other seafood.
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FAQ Frequently asked questions
What is listeriosis?
Listeriosis is a condition caused by Listeria monocytogenes bacteria. These bacteria are widespread in nature and can be found in the soil, water and in many animals. People most often get infected with Listeria after eating food that is contaminated with the bacteria.
What are the symptoms of listeriosis?
Symptoms of listeriosis resemble those of the flu and may include fever, chills, headache, feeling unwell, muscle pain and diarrhea. If the bacteria infect the nervous system or the blood, severe listeriosis can set in. Symptoms of severe listeriosis …
How is listeriosis diagnosed?
Listeriosis is diagnosed by laboratory testing of tissue samples and blood.
Will listeriosis clear on its own?
Most cases of listeriosis will clear after a few days. Complicated listeriosis in high-risk people requires medical attention.
How is listeriosis spread?
Listeriosis is spread via contaminated food. A pregnant woman can transmit the bacteria to her unborn baby.
Can listeriosis be prevented?
Although the chance of infection cannot be completely eliminated, listeriosis can be avoided by practicing good food-handling practices. People at risk can avoid risky foods.