Are You Still Proving the Negative with Your Environmental Listeria Program?

Posted by Mandi Kim, Food Safety Specialist on Mar 9, 2016 9:47:44 AM

Listeria.jpgIn light of recent events, food processors are starting to change how they view their environmental monitoring programs. Listeria recalls and outbreaks are occurring too often and now affecting a broader range of food products such as pet treats and caramel apples, which have not been linked with Listeria contamination in the past.  

This  combined with increased consumer awareness and recent regulatory requirements have placed a renewed focus on the importance in the development of more effective risk mitigation and preventative control strategies. As a result, food processors are now shifting their efforts in trying to find Listeria so that it can be eliminated from the processing environment before it’s too late.

Why is Listeria so hard to eliminate?

Listeria is truly a survivor. It can grow at refrigerated temperatures yet resist high temperatures that even Salmonella and E.coli can’t tolerate. It can live for extended periods of time in acidic conditions, especially in refrigerated foods. It can tolerate and even grow in high salt environments. And it can survive all of these situations with or without oxygen.


What attributes greatly to Listeria's survival in these harsh conditions is the ability to form biofilms, allowing it to withstand various food processing and preservation methods. The persistence of these biofilms can lead to pervasive issues on minor crevices and harborage sites throughout the manufacturing environment.

What can food processors do then?

In addition to having an effective cleaning and sanitation program, one of the most important steps in eliminating and controlling Listeria is identifying it, which is done through an environmental monitoring program.

For food processors, developing the right program for their specific manufacturing environment requires a substantial investment of both time and resources. However, one of the most critical yet often overlooked component is the pathogen detection method being used to validate and verify their cleaning and sanitizing programs are working.

The most common misconception is that all pathogen detection methods are the same. But when it comes to sensitivity, there are significant differences that could be putting your program at risk. Many methods require a significant level of growth prior to detecting positives. Sanitizers, cleaning agents, and even background flora can all attenuate the growth of Listeria, which enable true positives to fly under the radar. In addition, these sanitizers can interfere with the actual reactions of the test, potentially creating a risky false negative or a wasteful false positive.  To ensure the effectiveness of your environmental monitoring program and lower your risk for false results, it is critical to use a method sensitive enough to accurately pick up pathogens even at low levels regardless of sample type.  

What is the goal of your sampling program? 

If the primary purpose of your sampling program is to “Find the Positives”, then choosing a more advanced pathogen detection test method can help you achieve your goal to Seek & Destroy Listeria in your processing environment by providing you with a clearer picture of your processing environment that will accurately identify potential risk areas and allow you to take corrective action more quickly.


Proving the negative is no longer an option for today's environmental testing. While food processors are making significant investments in the development of preventative control programs, the effectiveness of these programs are only as good as the performance of the pathogen test method used to validate and verify it. In order to ensure the safety of their products, food manufacturers need to use a better detection tool that can provide a clearer, more accurate picture of the processing environment.

As the saying goes, "You can't control what you can't see."  

Where can I learn more about best practices for environmental testing?

When it comes to Environmental Testing for Listeria spp. a renewed understanding of the complexity of what is involved in the collection, enrichment, detection and culture confirmation of Listeria spp. is paramount to facilitate change and the drive towards a higher level of control.

To learn more about this topic, sign up for our upcoming webcast:

Culture Shift: The New Dynamics of Listeria Environmental Control and Testing

When:  April 6th, 2016
Time: 2:00 - 3:00 pm ET, 11:00am - 12 pm PT
Cost: Free

Register Today



Topics: Food Safety Technology, pathogen testing, Listeria Environmental