Food Recall Resource

Listeria Infection: Everything You Need to Know about this Dangerous Illness

Listeria infection is rare but can cause potentially life-threatening complications. Learn its causes, symptoms, risk factors, treatment, and preventive measures. 

Listeria infection, or listeriosis, is a serious foodborne bacterial infection caused by the bacterium Listeria monocytogenes. While listeriosis is not a serious problem for an otherwise healthy person, it can cause fatal complications (invasive listeriosis) in unborn babies and newborns, according to Mayo Clinic. People with weakened immune systems, such as those having HIV/AIDS or cancer, are also more vulnerable to fatal complications.

Listeria in pregnancy can lead to early miscarriage, stillbirth, premature delivery, or fatal infection of the newborn.

Unlike other foodborne infections, such as salmonellosis, it is less common and likely to be undiagnosed. Common listeria symptoms include fever and diarrhea. However, severe listeriosis can cause stiff neck, confusion, loss of balance, and convulsions.

Any specific treatment is not usually necessary for healthy kids, teens, and adults. The symptoms usually clear on their own within a few weeks. However, for pregnant women and newborns, the doctor may prescribe antibiotics to be administered into a vein.

Because the infection spreads through the consumption of contaminated foods, avoiding high-risk foods such as meats, frozen vegetables, and untreated milk can help reduce the risk of getting the infection.

What is Listeria?

It is a gram-positive bacterium commonly found in soil, water, and certain animals. There are six species of the bacterium. However, only Listeria monocytogenes is harmful to humans.

In contrast to other bacteria, it exhibits a high level of resilience and can survive both anaerobic (absence of oxygen) and aerobic (presence of oxygen) conditions.

The optimal temperature for its growth ranges from 86°F to 98.6°F. Interestingly, it is also known to multiply at refrigerator temperatures, which makes it a possible source of infection in the refrigerated foods.

It is an opportunistic bacterium, which means it becomes pathogenic only when a person’s immune function weakens or the person becomes old.

Listeria Signs and Symptoms

Most symptoms begin a few days after consuming contaminated foods. However, some persons may not have any symptoms until a month after the exposure.

The symptoms vary largely depending on a person’s general health and the site of the body affected by the bacteria.

The early signs and symptoms, which are similar to those of other foodborne illnesses, include:

  • Fever
  • Muscle aches
  • Nausea
  • Diarrhea

When the infection has spread to the nervous system, the patient is said to have invasive listeriosis and the symptoms can include:

  • Headache
  • Stiffness in the neck
  • Mental confusion or changes in alertness
  • Problems with balance
  • Convulsions

Infected pregnant women typically experience mild flu-like symptoms such as fever, fatigue, and pain in the muscles. Unfortunately, this can prevent the mother from seeking treatment, which can lead to devastating consequences such as miscarriage.

Symptoms in Newborns

  • Avoiding feeding
  • Fussiness
  • Fever
  • Vomiting

Causes of Listeria Infection

Consuming contaminated foods is the major cause of the infection. The common food sources of listeria include:

  • Uncooked vegetables/fruits that have acquired the bacteria from the soil or from contaminated manure, such as cantaloupe and cabbages
  • Animal meat that contains the bacteria
  • Untreated milk or foods prepared from untreated milk
  • Processed foods such as soft cheeses, hot dogs and deli meats that have acquired the bacteria during processing

Babies in the womb can acquire the bacteria from the mother.

What are the Risk Factors of Listeria?

An otherwise healthy adult with a competent immune system is less likely to get the infection. The following diseases or conditions significantly increase the risk:

  • Seniors aged 65 or older
  • AIDS (acquired immune deficiency syndrome)
  • Diabetes
  • Existing kidney disorder
  • Cancer chemotherapy
  • Liver diseases such as cirrhosis
  • Use of medications to treat arthritis or medications that reduce the body’s ability to fight infections

Listeria Treatment: Know Your Options

The choice of treatment varies depending on the severity of the condition. If the infected person is otherwise healthy, the doctor may not prescribe any specific medications. For such persons, adequate fluid intake and rest can help clear the symptoms.

If the infection has spread to the blood or the brain, the doctor can prescribe an antibiotic (ampicillin), or a combination of antibiotics (ampicillin plus gentamicin) to be given into a vein. Usually, the treatment lasts for up to 6 weeks.

Prompt antibiotic treatment to the pregnant women can help protect the unborn baby from the infection. Newborns with listeria may also be treated with antibiotics.

Serious Complications of Listeria Infection You Should Not Miss

A majority of listeria infection is not serious and hence is likely to be un–diagnosed. Nonetheless,

it can cause potentially fatal complications, which include:

  • An infection of the blood (septicemia)
  • Inflammation of the coverings of the brain (listeria meningitis)
  • Miscarriage if the infection starts within a first few weeks of pregnancy
  • Premature birth or stillbirth if the infection starts during the last trimester of pregnancy

How to Prevent Listeria Infection?

Luckily, listeria prevention is easy. Frequent hand washing and following simple food safety guidelines not only reduce the risk of listeria but also other foodborne illnesses like salmonella and E. coli.

  • Avoid drinking unpasteurized milk and eating foods prepared from unpasteurized milk.
  • Wash knives, cutting boards, and utensils with soap and water after you finish preparing uncooked foods.
  • Rinse raw fruits under running water for at least a minute to remove the bacteria.
  • Store raw meats, poultry, and seafood away from vegetables, fruits, cooked foods, and ready-to-eat foods.
  • Cook meat, poultry, and egg dishes to at least 160°F. You may use a meat thermometer to record the temperature.
  • Consume hot dogs as soon as you open the package, preferably within a week. Likewise, consume deli and luncheon meats within 4 days after opening.
  • Wash your hands properly after handling any raw fruits or vegetables.
  • Make sure the temperature in the refrigerator is below 40°F. If you use a freezer, keep the temperature below 0°F.

Listeria: Interesting Facts

  • Most patients are from the industrialized nations including the US.
  • Compared to other people, pregnant women are ten times more likely to get listeria. If the woman is Hispanic, the risk multiplies by twenty-four folds.
  • In the US, the annual treatment cost for listeriosis is $2.6 billion. This makes listeriosis the third costly foodborne illness, next only to salmonellosis and toxoplasmosis.
  • It is the cause of roughly 260 deaths annually in the US.
  • More than 90 percent of people with the infection need treatments at the hospital.
  • Compared to other foodborne illnesses, it is more dangerous as its mortality rate is more than 20 percent even when the patients receive antibiotic treatment.
  • The first confirmed case of listeriosis was reported in 1929.

In the 1980’s, there were several cases of large listeria outbreaks.

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