What is listeriosis? What causes listeriosis?
Listeriosis is an infection caused by a gram stain-positive motile bacterium named Listeria monocytogenes. The foodborne illness produces fever, muscle aches, and, in many people, diarrhea. Severe infections can cause headaches, meningitis, convulsions, and death. Most healthy people exposed to the bacteria have minor or no symptoms, but a few people, especially the elderly, pregnant females and their fetus, newborns, and anyone with a compromised immune system are especially susceptible to these organisms. Listeria bacteria are widespread throughout the world and are often associated with farm animals that may show no signs of infection. Research shows that many animals are uninfected carriers, and they suggest that some humans carry these organisms as part of their bowel flora. Except for pregnant women and their fetus or newborn, there is no direct transfer of Listeria from human to human.
The organisms (Listeria monocytogenes) that cause listeriosis have probably been infecting humans for centuries. Listeria was first isolated from an infected WWI soldier in 1918 and had many different names until 1940, when the genus and species names were firmly established. However, the bacteria were first recognized as a food-borne (food poisoning) pathogen in 1979. The bacteria can penetrate human cells and can multiply inside them. People with altered or impaired immune systems have cells that are less able to control the spread of these organisms into the blood or into other cells. In 2010, a known species, Listeria ivanovii, thought only to infect cattle, was found to infect humans so there are two Listeria species that can infect humans.
Outbreaks of listeriosis can occur with some frequency. For example, in 2017, soft raw milk cheese was a source of an outbreak (Vulto Creamery). In this outbreak, eight people were infected and two died. Other recalls of products in 2017 include 3 tons of cheese for possible Listeria contamination (La Nica Products INC.), macadamia nuts (Simple Truth brand), Ava’s Organic Cashews, and Queso Fresco cheese, for the same problem.
What are the risk factors for listeriosis?
Is Listeria contagious?
How is listeriosis spread?
What are listeriosis symptoms and signs?
- Fever, muscle aches, and occasionally, gastroenteritis (nausea and/or diarrhea) are the usual symptoms associated with listeriosis.
- Some individuals may also experience fatigue and a decrease or loss of appetite.
- These symptoms usually last up to one week and may spontaneously resolve.
However, in some people, the organisms can spread to the brain.
- The symptoms of meningitis and/or encephalitis (stiff neck, headache, and fever) may appear, including altered mental status (confusion and reduced mental activity),
- Loss of balance problems and seizures (convulsions) may develop in brain infections.
- Brain abscesses may also occur and cause similar symptoms.
What is the incubation period for Listeria?
The incubation period between exposure and symptoms is quite variable (three to 70 days, with 21 days as average) and may extend up to about two months or more according to some reports.
Pregnant women who are otherwise healthy usually have only minor symptoms. However, being infected with Listeria during pregnancy often cause problems for the fetus:
- premature birth, or
- cause infection and,
- potentially, death of newborns.
Breastfeeding in humans has not been shown to transmit the bacteria to newborns; however, animal studies show the organisms are transferred in breast milk of other mammalian species. Researchers consider it is theoretically possible for the organisms to be transmitted in human breast milk.
Occasionally, localized skin infections may occur, especially in people who handle animals that are infected with Listeria. These skin infections rarely lead to further complications such as brain infection.
How long does a Listeria infection last?
What types of doctors treat listeriosis?
How do health care professionals diagnose listeriosis?
What is the treatment for listeriosis?
The majority of people with Listeria infections spontaneously clear the infection in about seven days. However, those patients at increased risk, especially pregnant women, usually require immediate IV antibiotic treatment to prevent, halt, or slow the development of more severe disease. For example, early effective antibiotic treatment of pregnant females may be lifesaving for the fetus.
In general, the length of antibiotic treatment increases with the severity of the infection. Meningitis is treated for three weeks while brain abscesses are treated for six weeks. The initial choice of antibiotics is usually IV ampicillin. Bactrim (trimethoprim–sulfamethoxazole) also has been used successfully. However, each patient’s treatment should be individualized for optimal results; many clinicians recommend an infectious-disease consultant be involved, and if the patient is pregnant, her obstetrician and a pediatric specialist should help manage the treatment plan.
There are no over-the-counter diagnostic tests for listeriosis, so it will be difficult or impossible to know if you are infected with Listeria; that makes it difficult to decide if you can treat the problem at home. Because listeriosis can be fatal in about 20%-30% of those who develop the disease, home remedies may be a dangerous option without consulting a physician. However, there are suggestions to try, like activated charcoal, syrup of ipecac, garlic, and/or alcohol-free goldenseal to treat food poisoning in general. However, before trying any of these options, you should discuss them first with your doctor.
How does a person get listeriosis?
What are the complications of listeriosis?
The major complications of listeriosis include
- blood infection (septicemia/bacteremia),
- meningitis and/or encephalitis,
- brain abscesses,
- premature birth,
- neonatal sepsis (potentially fatal),
- stillbirth, and
Is it possible to prevent listeriosis?
Yes, listeriosis can be prevented. The CDC recommends the following food safety measures:
- Thoroughly cook raw food from animal sources, such as beef, pork, or poultry.
- Wash raw vegetables thoroughly (scrub with a clean produce brush in uncontaminated running water) before eating.
- Keep uncooked meats separate from vegetables and from cooked foods and ready-to-eat foods.
- Avoid unpasteurized (raw) milk or foods made from unpasteurized milk.
- Wash hands, knives, and cutting boards after handling uncooked foods.
- Consume perishable and ready-to-eat foods as soon as possible.
Here are food safety recommendations for people at high risk, such as pregnant women and people with weakened immune systems, in addition to the recommendations listed above:
- Do not eat hot dogs, luncheon meats, or deli meats, unless they are reheated until steaming hot.
- Avoid getting fluid from hot-dog packages on other foods, utensils, and food preparation surfaces, and wash hands after handling hot dogs, luncheon meats, and deli meats.
- Do not eat refrigerated pâtés or meat spreads. Canned or shelf-stable pâtés and meat spreads may be eaten.
- Do not eat refrigerated smoked seafood, unless it is contained in a cooked dish, such as a casserole. Refrigerated smoked seafood, such as salmon, trout, whitefish, cod, tuna or mackerel, is most often labeled as “nova-style,” “lox,” “kippered,” “smoked,” or “jerky.” The fish is found in the refrigerator section or sold at deli counters of grocery stores and delicatessens. Canned or shelf-stable smoked seafood may be eaten.
- Avoid cross-contaminating other foods, utensils, and food-preparation surfaces with fluid from hot-dog packages, and wash hands after handling hot dogs.
- Do not eat soft cheeses such as feta, Brie, and Camembert, blue-veined cheeses, or Mexican-style cheeses such as queso blanco, queso fresco, and Panela, unless they have labels that clearly state they are made from pasteurized milk. Cheeses that may be eaten include hard cheeses, semi-soft cheeses such as mozzarella, pasteurized processed cheeses such as slices and spreads, cream cheese, and cottage cheese.
- Do not drink raw (unpasteurized) milk or eat foods that contain unpasteurized milk.
There is no commercially available vaccine to protect against infection by Listeria.
If a person has eaten recalled food potentially contaminated with Listeria, what should he or she do?
The CDC recommends the following to all people. If the person has no symptoms, they recommend no tests or treatment be done. However, if the person is in a high-risk group (see risk factor section above), they recommend contacting the person’s physician only if the person develops fever or signs of serious illness within two months of eating the food. The CDC makes these conservative suggestions based on the fact that the chance of developing Listeria infection, even after ingestion of a contaminated product, is very small.
However, people in the high-risk groups should have no delays in contacting their doctor if they suspect symptoms of listeriosis are developing.
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