Listeria monocytogenes

Listeria monocytogenes, a bacteria discovered in 1911, causes the disease listeriosis. It was first noted as a food-borne illness in the 1980s and is now the 3rd most common food-borne illness. A recent outbreak of Listeria from deli meat and cheese has it back in the news.   

About 15-20% of those infected will die from this disease. Immunosuppressed persons, persons over 65, newborns and pregnant women are the most susceptible to Listeria complications. In these persons listeria infection can become septic, meaning it spreads throughout the body. Additionally, a quarter of all intrauterine (pregnancy) infections leads to miscarriages and stillbirths.

It is a hardy bacteria living in many different environments worldwide hot or cold including the soil, water and your fridge. It can grow in refrigerated temperatures which makes it hard to avoid in prepared or packaged foods. Listeria also survives freezing, drying, and alcohol cleaners. It can cause a huge range of infections throughout the body. 

Infections caused by Listeria:

• Flu-like illness

• Meningitis-infection of the lining surrounding the brain

• Encephalitis-brain infection

• Sepsis-affecting the blood stream

• Skin infections -click here for more on how these lead to body odor

• Gastroenteritis-infection of the stomach and intestines

• Infection of joints and prosthetic joints

• Osteomyelitis-infection of the bone

• Infection inside the abdominal or chest cavity 

• Infection in the eyes

What causes Listeria infections?

• Eating soft cheeses

• Eating cold deli meat

• Eating hotdogs not heated up

• Eating melons

• Eating raw vegetables

• Exposure to livestock (skin infections)

• Exposure to a contaminated source such as sitting water 

• Eating raw meat

• Consuming unpasteurized milk or milk products

• Eating packaged smoked salmon or raw seafood

How is Listeria diagnosed?

Most infections are asymptomatic—meaning the person has no symptoms and doesn’t know they are infected. Studies have shown 5% of random stool cultures were positive for Listeria monocytogenes. So, clearly, a stool culture would not be an effective means of diagnosing listeria. In addition, it can take up to 2 months after listeria exposure to develop symptoms. 

Blood cultures, skin cultures and spinal cultures are the best means of diagnosing Listeriosis/listeria infection. 

What are the symptoms of Listeria infection?

• Fever

• Vomiting

• Headache

• Diarrhea 

• Pain or swelling of a joint, skin, eye, abdomen or chest area

• Body aches

• Convulsions

• Stiff neck

How do I prevent Listeriosis?

• Always heat your hot dogs prior to eating. 

• Wash your vegetables well. 

• If you are at risk, such as being pregnant, immunocompromised or elderly, then heat all deli meat and smoked salmon thoroughly prior to eating. 

• Avoid soft cheeses. 

• Wash yourself off after exposure to livestock. 

• Only consume pasteurized milk and milk products. 

• Do not eat raw meat. 

• Do not eat raw shellfish. 

How is Listeria treated?

Remember, most people do not know they were exposed or infected. Listeria bacterium is quite common and ingested by more humans than it causes noticeable infections. While infections are rare, once they do happen they can lead to serious complications and have a high death rate. 

Most patients are hospitalized and treated with IV antibiotics. 

Have there been outbreaks of Listeriosis?

Yes, there are multiple documented outbreaks of Listeriosis throughout the world. 2022 alone has seen numerous food recalls due to listeria contamination. This recall list is quite extensive. The most recent was in the fall of 2022. Six states from New York to California had a listeriosis outbreak due to contaminated deli meats and soft cheeses. 

The Canadian Food Inspection Agency recalled packaged Enoki mushrooms in September 2022. The mushrooms were distributed by WK Produce and were recalled due to Listeria contamination. Thankfully, it was found prior to any known human infections.

Circle K in Canada recalled sandwiches due to Listeria in October of 2022. That same month listeria caused the recall of cheeses from Gaton’s Foods Dairy of Canada. 

One outbreak in the U.S., caused by Dole brand packaged salad products, lasted from 2014 to 2022! The investigation for the source of this recurrent outbreak re-opened in 2021 finally leading to the cause and subsequent recall of the Dole products. 

Infected Tyson foods fully cooked frozen chicken led to a recall in 2021 in the U.S. 

Blue Bell frozen deserts were the cause of an outbreak from 2010 to 2015. 

In 2011, 28 U.S. states had infections and deaths due to listeria tainted cantaloupe from Colorado. 

These recalls are just an example of the wide range of products that Listeria can infest. This also brings to light the number of recalls in such a short time frame and all the recalls caused by household names.

How do I find recalls in my area?

For recalls and public health alerts in the U.S. click here. 

For U.S. safety recalls and market withdrawals click here. 

For food recalls in the U.K. click here. I found the U.K. site quite interesting. Most of the recent recalls were actually due to food contaminated by plastics or metals. 

For all types of recalls in Canada click here. 

Conclusion:

Though this disease may be rare it is prudent to recognize it early, especially if you are at risk. Follow the above recommendations for prevention and see your doctor immediately if you have any exposure or risk of a Listeria infection. Remember it can take up to 70 days/2 months after exposure for infection to appear and at-risk persons are those over 65 years old, pregnant, or immunocompromised.