Listeriosis and Its Causative Organism – Diagnosis and Treatment

Listeriosis is a food borne illness caused by the bacteria, Listeria monocytogenes, that thrive in cold environments. Listeria monocytogenes is found in animal intestines, as well as in soil, water, and plants.

What Exactly is Listeria Monocytogenes?

Listeria monocytogenes is a type of bacteria that can be found in soil and water. Animals carry it without becoming ill, contaminating animal-derived foods such as meat and dairy products. This organism can contaminate vegetables grown in soil fertilized with tainted manure.

Who is Susceptible to Listeriosis?

Anyone can get the disease, but pregnant women, the elderly, people with weakened immune systems (for example, people with cancer, HIV/AIDS, or a transplant), and people with chronic liver or kidney disease, diabetes, or alcoholism are at higher risk.

When healthy adults and children become infected with Listeria, they rarely become seriously ill. Although the majority of cases are isolated incidents, food-borne outbreaks (when two or more people become ill from the same source) do occur.

Which foods are the most frequently contaminated with Listeria monocytogenes?

Animal foods are the most contaminated by listeria monocytogenes; examples of such foods include:

  1. Unpasteurized milk
  2. Listeria monocytogenes can be found in soft cheeses such as feta and brie, as well as raw vegetables.
  3. Poultry, meats (including hot dogs and lunch meat), and ready-to-eat prepared, chilled foods are also at risk.


How is Listeria Monocytogenes killed?

Listeria monocytogenes can only be killed by the action of heat on food.

Listeria is killed by pasteurization and heat used in the preparation of ready-to-eat processed meats.

Contamination can, however, occur after processing. Listeria multiplies and grows at refrigeration temperatures every day the contaminated product is stored.

What are the signs and Symptoms of Listeriosis?

If you get a listeria infection, you could have

  1. Fever
  2. Chills
  3. Muscle aches
  4. Nausea
  5. Diarrhea
  6. Vomiting

Symptoms may appear a few days after eating contaminated food, but it may take 30 days or more for the first signs and symptoms of infection to appear.

If the listeria infection spreads to your nervous system, you may experience the following signs and symptoms:

  1. Headache
  2. Stiff neck
  3. Confusion or changes in alertness
  4. Loss of balance
  5. Convulsions

Listeria monocytogenes typically causes a flu-like illness with fever and chills in pregnant women.

Complications of Listeria Monocytogenes

The majority of listeria infections are so mild that they go unnoticed. In some cases, however, a listeria infection can result in life-threatening complications, such as:

  1. Generalized blood infection
  2. Inflammation of the membranes and fluid that surround the brain (meningitis)

How is Listeria monocytogenes identified?

Only specific laboratory tests can be used to diagnose this disease. If the disease is present, a blood, spinal fluid, or amniotic fluid/placenta test that looks for bacteria will be able to detect it.

What is the cure for Listeriosis?

Antibiotics are used to treat listeriosis. Ampicillin can be used alone or in conjunction with other antibiotics.


To avoid a listeria infection, you must do the following:

  1. Maintain a clean environment.
  2. Thoroughly wash your hands with warm, soapy water before and after handling or preparing food.
  3. Cook your food completely.
  4. Make sure your meat, poultry, and egg dishes are cooked to a safe temperature by using a food thermometer.
  5. Cook raw animal foods such as beef, pork, or poultry to the proper temperature. 145 degrees Fahrenheit for whole meats, plus 3 minutes of stand time for safety. No stand time is required for ground meats at 160°F. 165 degrees Fahrenheit for all poultry, whether ground or whole.
  6. Before eating raw vegetables, thoroughly wash them.
  7. Separate the uncooked meats from the vegetables, cooked foods, and ready-to-eat foods.
  8. After cooking,make sure to wash the utensils, cutting boards, and other food preparation surfaces with hot, soapy water.
  9. Clean raw vegetables.
  10. Under running water, scrub raw vegetables with a scrub brush or vegetable brush.
  11. Unpasteurized (raw) milk and foods made from unpasteurized milk should be avoided.
  12. Perishable and ready-to-eat foods should be consumed as quickly as possible.
READ MORE: Irritable Bowel Syndrome and Its Significance in Healthcare

Detailed Overview Of Listeria Infection, Diagnosis and Treatment

Many people who get listeriosis have fever and muscle aches. Gastrointestinal symptoms such as nausea or diarrhea may also occur. If infection spreads to the nervous system, a headache, stiff neck, confusion, loss of balance or convulsions can develop.

A blood test or spinal fluid test looking for the bacteria can confirm the diagnosis. Treatment involves antibiotics such as ampicillin alone or in combination with gentamicin.

Symptoms Of Listeriosis

The symptoms of listeriosis include fever, muscle aches and gastrointestinal discomfort such as diarrhea. In some cases, the infection can lead to more serious problems like meningitis and even death.

The bacteria can get into the body through contaminated food. It is most commonly found in deli meats and dairy products that haven’t been pasteurized. It can also get into people who have contact with infected animals.

In healthy people, listeriosis is generally mild and self-limiting. For those who are at higher risk of getting seriously ill, treatment with antibiotics is usually required.

Pregnant women, infants and those with weakened immune systems are at highest risk of listeriosis. If the infection is not treated in high-risk pregnant women, it can cause miscarriages and stillbirths. In babies and those with weakened immune systems, it can cause life-threatening problems including sepsis and meningitis.

Most often, the first signs of listeria are a low-grade fever and a headache. Some people may also have a stiff neck or confusion. People who are diagnosed with the condition might have a blood or spinal fluid test to confirm their diagnosis.

The most common treatment for listeriosis involves taking a medication called ampicillin. It is often given in combination with a drug called gentamicin.

Symptoms typically begin to improve within about a week of starting medication. For more severe infections, hospitalization might be necessary.

To prevent listeriosis, people should wash all produce thoroughly. They should also ensure that raw meats are cooked until steaming hot. In the fridge, people should separate ready-to-eat foods from raw food items and keep meats and eggs in their own compartment. They should also clean all cutting boards and utensils after handling them.

Health professionals should educate the public on how to reduce their risk of listeriosis by promoting good food safety practices. This includes washing all fruits and vegetables thoroughly, cooking meats and eggs to proper temperatures and keeping refrigerated foods cold at all times. If someone is unsure whether a food product is safe to eat, they should call 111 or visit their local health department.

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Diagnosis Of Listeriosis

Listeria is a bacteria that can cause fever, headache, stiff neck, confusion, and loss of balance. It can be found in soil, water, and the faeces of animals, including wild and domestic. It can also be transmitted to humans through infected food, and most people infected with listeriosis develop an intestinal illness with diarrhea. In rare cases, the infection can be more serious and invasive. People with invasive listeriosis can develop meningitis, brain stem encephalitis (rhomboencephalitis), or other infections that affect the central nervous system. Other complications of the infection include a heart attack, infected prosthetic joints, and localised internal abscesses. Listeriosis can also be fatal.

Generally, doctors diagnose listeriosis by taking a blood sample and looking for the presence of the bacteria, or a DNA sample from the placenta in pregnant women who have a high risk of contracting it. Doctors can also test stool samples for the bacteria. In some countries, doctors may need to take samples from other parts of the body if they suspect the patient has a more severe form of the disease.

Pregnant women have a much higher risk of developing listeriosis than other adults because of the changes to their immune systems that occur during pregnancy. They are 10 times more likely to get the disease than non-pregnant women, and they can pass it on to their unborn babies. Newborns infected with early onset listeriosis can have severe symptoms such as septicemia and meningitis. They can be hospitalized and die. Invasive listeriosis in non-pregnant people 65 years of age or older, and those with weakened immune systems, usually develop infection of the bloodstream, or septicemia, or infections that affect the brain (meningitis or encephalitis).

Infection with the bacteria typically results from eating foods contaminated with Listeria. Antibiotic treatment is effective against the disease if it is given quickly after the diagnosis. Doctors are more likely to prescribe antibiotics if the patient is pregnant, over the age of 65, or has a weakened immune system. The most common antibiotics used to treat listeriosis are sulfamethoxazole and ampicillin.

Treatment Of Listeriosis

Anyone can get listeriosis, but it usually affects the elderly, infants, and those with weakened immune systems. It’s more likely to appear after eating contaminated food, especially ready-to-eat cold smoked or cured fish products (like gravlax) and dairy products made from unpasteurized milk. The symptoms can be mild and last a few days, or they could be much more severe.

The most common symptom is fever, muscle aches and sometimes gastrointestinal symptoms like nausea or diarrhea. If infection spreads to the nervous system, symptoms like headache, stiff neck, confusion or loss of balance may occur. In pregnant women, listeriosis can cause miscarriage, stillbirth or life-threatening infection of the newborn.

Doctors diagnose listeriosis by doing a blood test to see if the bacteria are present. They may also take a sample of spinal fluid or the placenta in infected pregnant patients to look for signs of meningitis. They can also treat the disease with antibiotics.

Listeriosis is treated with antibiotics such as ampicillin and gentamicin. Ampicillin can be used as a single agent, or in combination with other antibiotics such as sulfamethoxazole and trimethoprim. Other antibiotics that can be used include erythromycin, vancomycin and imipenem. Infections caused by Listeria monocytogenes that don’t involve the nervous system can be treated with shorter durations of antibiotics, as outlined in Table 3. Patients with bacteremia and meningitis should be treated for two weeks or longer. Rhombencephalitis and brain abscesses may need treatment for six to eight weeks.

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The risk of listeriosis from foods is low, but it’s important to avoid contaminated foods. Pregnant women and those with weakened immune systems should be particularly careful, and shouldn’t eat deli meats or other contaminated foods that have been refrigerated for long periods of time.

People with weakened immune systems should also be very cautious about consuming raw or undercooked seafood, as these are high risk foods for Listeria infections. They should also wash their hands frequently after handling perishable foods or going to the toilet. They should also avoid contact with animals, particularly if they are nursing or have recently given birth.

Prevention Of Listeriosis

Although anyone who eats contaminated food can get listeriosis, pregnant women and people with compromised immune systems are at higher risk. Infection during pregnancy can lead to miscarriage, stillbirth, or infection of the newborn. Elderly people can develop a serious blood infection or meningitis (inflammation of the lining around the brain and spinal cord).

Most healthy people who eat Listeria-contaminated foods do not get sick. When someone with a normal immune system gets infected, they usually have fever and muscle aches. Some may also have gastrointestinal symptoms like nausea or diarrhea. People with compromised immune systems can get a more severe illness, including headache, stiff neck, confusion, loss of balance and convulsions.

The bacteria can be spread by eating contaminated foods, but only in very small amounts. It can also be transferred from one person to another by kissing, sneezing or breathing in droplets containing the bacteria. Infections from these sources typically occur after an exposure of less than three days.

Listeria is found in the environment, particularly soil and water. It can also live in the intestines of domestic and wild animals. Infections are most common in persons who handle raw meat or unwashed produce. It can also be spread by drinking contaminated milk and from consuming ready-to-eat deli meats and hot dogs, especially if they have not been heated to 160 degrees before serving.

There are no vaccines to prevent listeriosis. Infections can be prevented by thoroughly washing hands while preparing food and before eating. Keeping raw and cooked foods separate reduces the chances of contamination, and making sure that all meat is fully cooked until it has a minimum internal temperature of 160 degrees (beef, pork, veal or lamb) or 165 degrees (turkey and chicken). Respecting shelf-life and storage temperatures on labels of RTE foods can also help prevent infections. Continuous education of consumers, particularly those in high-risk groups, is critical to improving food safety practices. It is also important to educate food handlers about proper cooking and handling techniques. This includes people who work in restaurants, grocery stores and child care centers.

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