Listeria

Listeria monocytogenes is pathogenic to animals and humans. The bacteria can be found in some foods, but also in water, soil, vegetation, animal feces, storage bins and slaughterhouse waste. Listeria is a bacterium that is sensitive to heat. It can still survive and multiply at 4°C, the usual temperature of refrigerators. 
 
Listeria-related infections usually occur as a result of eating contaminated food such as:  

• deli meats and ready-to-eat meat products 
• unpasteurized milk and raw or soft cheeses 
• fish and seafood 
• fruits and vegetables. 

This bacterium can be transmitted from mother to child through the placenta or during childbirth, when the newborn passes through the birth canal. Farmers and veterinarians can also become infected at the time of farm animal birthing. In addition, farmers may be at risk when slaughtering animals for their meat.  

Points to keep in mind when sampling for listeria:  

• Always provide a sterile, airtight container to store samples.  
   
• Store the container on ice packs until laboratory analysis.  
   
• If samples are frozen, do not thaw them before analysis.  
   
• For surface samples: collect at least two wipes/swabs/socks.  
   
• For solid sampling: take a sample of at least 100 g.  
   
• For liquid sampling: take a sample of at least 100 ml.  

Listeria can cause listeriosis, a serious disease. People with weakened immune systems are at greater risk of complications. Although Listeria infections are relatively rare, they can be very serious and potentially fatal.  

Listeria is a bacterium that is difficult to detect. It does not change the appearance, taste or odour of products. It can be eliminated by pasteurization and cooking of food.  
 
As is the case with many foodborne illnesses, the risk of Listeria infections can be reduced by following general food safety recommendations, such as:  

• keeping food at the right temperature;
• proper cooking of food (see Safe Cooking Temperatures  according to the Government of Canada)
• consuming and using treated or bottled water; 
• separating raw and cooked foods.

For more details and tips, visit the Government of Canada website for General Food Safety Tips.