Listeria Monocytogenes – Transmission and Symptoms

You’ve been hearing about how good bacteria can be and even the numerous benefits of bacteria to humans e.g. the bacteria in the human gut and its importance in aiding the process of digestion. However, in this article we will be looking at the dangerous or bad sides of bacteria. As you know, there are two major categories of bacteria and they are the friendly and harmful bacteria. So we will be talking about harmful bacteria and to be specific the Listeria Monocytogenes bacteria.

Listeria monocytogenes is a tiny microorganism (bacterium) that causes severe and sometimes fatal infections in its hosts which are humans. This bacterium is commonly found in soil and water, and it can also contaminate food products, particularly those that are refrigerated or have prolonged shelf lives, so understanding the transmission, symptoms, and prevention of this bacteria is important to keeping yourself and others safe.

Listeria monocytogenes


What is Listeria monocytogenes?

Listeria monocytogenes is a type of bacteria that belongs to the genus Listeria. This bacterium is a Gram-positive bacterium that is widely distributed in the environment and can survive in extremely cold temperatures, making it a common contaminant of refrigerated foods. It was first identified as a human pathogen in the 1930s, and it has since been responsible for several large foodborne outbreaks.

The importance of this bacteria cannot be overstated, as it is a major cause of foodborne illness and death, particularly in vulnerable populations such as pregnant women, older adults, and individuals with weakened immune systems. In this blog post, we will explore the transmission and sources of Listeria monocytogenes, its symptoms and health effects, diagnostic and treatment options, and prevention and control measures.

Transmission and Sources of Listeria monocytogenes

Listeria monocytogenes can be found in a variety of food products, including raw and processed meats, dairy products, and vegetables. This bacterium can also be found in soil, water, and in the feces of infected animals. Food products that are commonly contaminated with Listeria monocytogenes includes ready-to-eat foods such as;

  •  Hot dogs
  • Deli meats
  • Refrigerated pâtés and meat spreads etc.

Transmission of Listeria Monocytogenes

The transmission of Listeria monocytogenes can occur through several routes which includes;

Foodborne transmission or ingesting contaminated food:

It can be present in contaminated food, particularly in raw or undercooked meat, poultry, seafood, and unpasteurized dairy products. It can also be found in ready-to-eat foods, such as deli meats, hot dogs, and soft cheeses.

Environmental transmission:

It can be present in soil, water, and other environmental sources. It can contaminate food during harvesting, processing, packaging, and transportation.

Person-to-person transmission:

It can be transmitted from person to person through direct contact with bodily fluids or feces, although this is rare.

Vertical transmission:

Listeria monocytogenes can be transmitted from a pregnant woman to her unborn child, which can result in serious complications for the baby.

Nosocomial transmission:

Listeria monocytogenes can be transmitted in healthcare settings, particularly in neonatal units or intensive care units, where patients may be more susceptible to infection.

Symptoms of Listeria Monocytogenes

The symptoms of Listeria monocytogenes infection can vary depending on the individual and the severity of the infection. While some people may not experience any symptoms at all, others may experience mild to severe symptoms. The onset of symptoms can range from a few days to several weeks after exposure to the bacteria.

The most common symptoms of Listeria monocytogenes infection includes;

  • Fever
  • Muscle aches, and 
  • Gastrointestinal symptoms such as nausea, vomiting, and diarrhea. 

In more severe cases, the infection can lead to sepsis, meningitis, and encephalitis. These serious complications can be life-threatening, especially in individuals with weakened immune systems, such as pregnant women, newborns, elderly individuals, and those with chronic illnesses.

Pregnant women are at particular risk of Listeria monocytogenes infection, as it can result in;

  •  Miscarriage
  • Stillbirth
  • Premature delivery, or a life-threatening infection in the newborn. 

So, it is very important for pregnant women to take extra precautions to avoid exposure to Listeria, such as avoiding certain foods and practicing good food hygiene.

In individuals with weakened immune systems, Listeria monocytogenes infection can also lead to severe illness and even death. People with HIV, cancer, diabetes, or other conditions that affect the immune system are at higher risk of developing serious complications from the infection.

If you suspect that you may have been exposed to Listeria monocytogenes, it is important to seek medical attention right away. Your healthcare provider can perform tests to confirm the presence of the bacteria and can provide treatment to help manage your symptoms and prevent serious complications.

Prevention of Listeria Monocytogenes

To prevent Listeria monocytogenes infection, it is important to practice good food hygiene, such as washing your hands before and after handling food, cooking foods to the appropriate temperature, and avoiding high-risk foods such as raw or undercooked meat, soft cheeses, and unpasteurized milk. By taking these precautions, you can reduce your risk of infection and protect your health.