Protecting Yourself Against Listeria: A Refresher Course

By: Sample6 on June 1st, 2016

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Protecting Yourself Against Listeria: A Refresher Course

Bacteria  |  Food Safety Education  |  Industry News  |  Listeria

It seems like in recent months and weeks, you just can't seem to escape the news of some type of food recall or without hearing about an outbreak of food contamination at a local restaurant. The CDC has been working with the USDA, FDA, and state/local public health officials to investigate these recent outbreaks caused by Listeria monocytogenes.

So, how can you protect yourself from Listeria? Let's first start with the basics. 

What is Listeria?: 

Listeria Testing: A Refresher CourseListeria monocytogenes is the bacteria that causes the infection listeriosis. Listeriosis is a leading cause of death among foodborne related sickness and death. It is estimated that 1600 illnesses and 260 deaths each year are caused by listeria.

People with weaker immune systems such as young children, pregnant women, cancer and AIDS patients, people with diabetes, and the elderly are more susceptible to Listeriosis and are more likely to have a more severe case. 

Listeria are very small and cannot be seen with the naked eye, making them challenging to detect when it comes to food safety. Even one single bacterium has the potential to make one sick because they can rapidly multiply. Understanding Listeria, where it grows and where to sample, is critical in keeping food processing facilities safe.

Where does it come from? 

Listeria is usually found in soil and water. It thrives in cold, wet environments. Ready-to eat foods that are produced in cold and wet environments are at risk for Listeria from environmental contamination. This includes ready-to-eat deli meats, hot dogs, unpasteurized milk and dairy products, raw sprouts, refrigerated meat spreads and smoked seafood. 

Listeria can be found on both the food itself and also the surfaces and machinery used to process the food, therefore contaminating it in the process. Listeria testing needs to be taken seriously and diligently. 

How does food get contaminated? 

Recent recalled products included frozen spinach and vegetables, hummus, and ice cream. Pasteurization, typically of milk and ice cream, takes care of any pathogens found in the raw materials. However, the product is still at risk for environmental contamination if niches exists in their facility. These niches are typically found in wet areas like drains and other areas of condensation like light fixtures or the ceiling.  

Another way ice cream could be getting contaminated is through the ingredients that are added after the pasteurization. For example, if you add cookie dough or chocolate chips, these additional ingredients could be contaminated. 

How Can You Protect Yourself? 

The U.S. Centers for Disease Control and Prevention (CDC) recommends washing fruits and vegetables very well. This also includes produce with a peel, like an orange. For 'harder' fruits and vegetables, like zucchini, melon and cucumbers, the CDC recommends scrubbing them with a brush. Other preventative measures include:

  • Keeping your kitchen clean
  • Washing kitchen countertops before and after cooking
  • Cleaning out your fridge on a regular basis.
  • Keeping your refrigerator at 40°F or lower and the freezer at 0°F or lower
  • Eating precooked foods as soon as possible. For example, deli meats should not be consumed after 5 days in the fridge. 
  • Consuming leftovers within 4 days from cooking. 

How Do Food Manufacturers Prevent Listeria Contamination?

The FDA has established industry guidelines for food manufacturers to help protect consumers against Listeriosis. These are just a few of the potential sources of Listeria in a plant:

  • Ingredients: Raw meat, poultry, seafood, milk, produce.
  • Processing Aids: Compressed air, ice, brine solutions
  • Contact Surfaces: including conveyor belts, slicers/shredders, utensils, gloves, filing/packaging equipment. 
  • Other Plant Surfaces: such as: in-floor weighing equipment; cracked hoses; equipment framework; tools for cleaning equipment, etc. 
  • Plant environment: Floors, walls and drains; ceilings, overhead structures, wash areas; standing water, etc. 

With all these potential risks, the FDA has extensive recommendations and guidelines for: 

  • Personnel/training
  • Design/construction and operation of the plant
  • Design/construction and operation of equipment 
  • General Sanitation Programs  
  • Cleaning Drains
  • Transportation of Foods
  • Monitoring critical plant surfaces and areas
  • Storage practices

Periodic sampling and testing of finished refrigerated (RF) and ready-to-eat (RTE) foods that are processed is also crucial in controlling listeria over time. It is recommended that a plant has a written plan that includes the frequency of sampling. If listeria is detected on a critical surface area, a corrective plan needs to be followed including: 

  • Cleaning/sanitizing the contaminated surface
  • Conducting additional sampling/testing to determine if the contamination has been eliminated
  • Review production, maintenance and sanitation procedures
  • Interview/observe all production employees to determine if proper procedures were followed. 

There are also extensive guidelines in place to create a critical action plan if listeria is detected in the food samples. Enrichment used to be the only way to ensure that all levels of bacteria could be detected. Because most food manufacturing plants don’t want to enrich pathogens near their food production, this requires sending samples to an external laboratory facility followed by 24-48 hours of enrichment process.

Sample6 Faster Detection for Listeria Contamination

SAMPLE6 Means faster detection

The good news is that Sample6 allows for the speed and flexibility of testing in the food processing facility itself. Sample6 DETECT/L, offers the only enrichment-free, AOAC certified 7-hour Environmental Listeria Species test.

It was originally thought that enrichment was necessary in order to detect low contamination levels of Listeria, but we found a way to skip enrichment and still keep our results sensitive and accurate.