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Recap of the Elo Qualité webinar: Food Safety – Fast, Optimized Environmental Monitoring
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Listeria monocytogenes: the cold-resistant pathogen threatening your production lines
Listeria monocytogenes is the deadliest zoonosis monitored in Europe. For food, feed, and pet food manufacturers, it’s also the pathogen hardest to eradicate once established in the production environment. Here’s what you need to know, and how to detect it before it becomes a problem.
Download the complete Listeria fact sheet
A technical, summary resource designed for quality and HACCP managers:
- Detailed regulations by region (EU, North America, Middle East, Africa)
- Key figures and the most recent epidemiological data
- Concrete risks for your production lines
- Overview of detection methods
What is Listeria?
301 deaths in 2024 in the EU.
Listeria monocytogenes has the heaviest death toll among all foodborne zoonoses under surveillance.
Source: EFSA/ECDC, The European Union One Health 2024 Zoonoses Report
Listeria monocytogenes is a ubiquitous bacterium, present in soil, water, plants, and both agricultural and industrial environments. What sets it apart from most foodborne pathogens: it is psychrotrophic. It survives and keeps multiplying slowly even in the cold, down to temperatures near 0°C. The cold chain alone is therefore not enough to control it.
It also tolerates high salt concentrations and withstands moderate acidity well, allowing it to colonize food matrices sometimes thought to be protected. Only thorough cooking (above 70°C) reliably eliminates it.
Why is it a specific risk for food, feed, and pet food manufacturers?
The real challenge is almost never the raw material. It lies in cross-contamination post-process, meaning after heat treatment, within the packaging environment itself. Listeria monocytogenes is able to form biofilms, bacterial communities protected by a matrix they secrete themselves, which resist standard cleaning and disinfection protocols. Once a biofilm is established on a surface (stainless steel, plastic, machine gasket), it becomes a source of recurring contamination, sometimes for months, with no apparent link to a one-off incident.
Which products and production areas are most exposed?
The products most at risk are those consumed with no cooking:
Sliced deli meats
Raw-milk and soft cheeses
Smoked fish
Vacuum-packed products and long-shelf-life refrigerated ready meals
The most critical areas are:
- Post-heat-treatment packaging areas,
- Wet, cold areas,
- Drains
- Conveyors,
In other words, every point where the product can be recontaminated after being made safe.
What does the 2026 regulation say about Listeria?
The regulatory framework is changing significantly. In Europe, Regulation (EC) 2073/2005, amended by Regulation (EU) 2024/2895, becomes applicable on July 1, 2026. In practice, for ready-to-eat products that allow Listeria to grow, the operator will now have to demonstrate, through shelf-life studies, that the 100 CFU/g threshold will not be exceeded throughout the product’s shelf life, not just at the time it leaves the plant. Without this evidence, the strictest criterion, total absence in 25g, applies automatically.
This tightening is seen in several regions worldwide, with similar approaches in North America (FDA and USDA zero tolerance) and Morocco (ONSSA order aligned with the European regime).
What are the risks for consumers?
For most healthy people, the infection often goes unnoticed or is limited to mild digestive symptoms. The risk becomes serious for pregnant women, newborns, the elderly, and immunocompromised people, in whom invasive listeriosis can cause sepsis, meningitis, or severe pregnancy complications. The case-fatality rate for these invasive forms reaches 20 to 30%, one of the highest among foodborne infections. Another distinctive feature: the incubation period can range from a few days to several weeks, which considerably complicates identifying the food responsible.
How can you detect Listeria quickly, before it contaminates the finished product?
Faced with a pathogen that settles durably into the production environment, regular environmental monitoring (surfaces, equipment, risk areas) is now recognized as the most effective detection lever, well ahead of finished-product control alone.
The LoopDeetect range lets you quickly screen surfaces and the production environment, with:
From sampling to result in under 90 minutes
To react quickly, put corrective actions in place, and limit the impact of contamination
A method that's simple to integrate and use on-site
A method with no enrichment, no handling, and no lab equipment. With ready-to-use devices and reagents.
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Recap of the Elo Qualité webinar: Food Safety – Fast, Optimized Environmental Monitoring
Read more »Frequently asked questions about Listeria
Under what conditions does Listeria monocytogenes grow?
Listeria monocytogenes is a psychrotrophic bacterium, meaning it keeps multiplying slowly even in the cold, down to temperatures near 0°C. It also tolerates high salt concentrations and withstands moderate acidity, allowing it to colonize foods sometimes thought to be protected. Cooking to a core temperature above 70°C reliably eliminates it, but this step alone is not enough to secure a product: the main risk comes from recontamination after this heat treatment, when the already cooked or pasteurized product comes into contact with contaminated equipment, a surface, or a packaging environment. It’s this combination of resistance to cold, salt, and acidity, plus post-heat-treatment vulnerability, that makes Listeria a particularly hard-to-control microbiological hazard in food processing.
Source: FDA, Draft Guidance for Industry on Listeria monocytogenes; van der Veen et al., 2008.
Which foods are most at risk of Listeria contamination?
The most exposed products are those consumed with no cooking after manufacturing, since they offer no final thermal barrier against the bacterium. Leading the list are sliced deli meats, raw-milk and soft cheeses, smoked fish, and vacuum-packed products and long-shelf-life refrigerated ready meals. These ready-to-eat products are, moreover, at the heart of European regulatory microbiological criteria. The risk isn’t so much tied to the starting ingredient as to the absence of a cooking step able to eliminate any contamination that occurred after manufacturing.
Source: Regulation (EC) 2073/2005; FDA Draft Guidance.
What is the new European regulation on Listeria in 2026?
Since July 1, 2026, Regulation (EU) 2024/2895, which amends Regulation (EC) 2073/2005, has applied in Europe. In practice, for ready-to-eat products that allow Listeria to grow, the manufacturer must now demonstrate, through documented shelf-life studies, that the 100 CFU/g threshold will not be exceeded throughout the product’s shelf life, not just at the time it leaves the plant. Without this evidence, the strictest criterion applies automatically: total absence in 25 grams up to the use-by date. This change turns an obligation of result into a genuine obligation of proof for quality managers.
Source: Regulation (EU) 2024/2895, EUR-Lex.
Why is Listeria monocytogenes hard to eliminate in a food plant?
Listeria monocytogenes is able to form biofilms, genuine bacterial communities that aggregate on a surface and protect themselves within a matrix they secrete themselves. This structure resists standard cleaning and disinfection protocols and can persist for months on equipment such as stainless steel, plastic, or machine gaskets. Once a biofilm is established, it becomes a recurring source of finished-product contamination, often with no apparent link to a one-off incident. This is why the fight against Listeria in a plant relies as much on the hygienic design of equipment as on cleaning itself.
Source: Chavant et al., Applied and Environmental Microbiology, 2002.
What is the difference between Listeria monocytogenes and other Listeria species?
The genus Listeria today includes nearly thirty different species, but only two are recognized as pathogenic to humans and animals: Listeria monocytogenes and Listeria ivanovii. Listeria ivanovii, however, remains very rare, mainly associated with infections in ruminants, with only a few sporadic human cases documented in the scientific literature. Listeria monocytogenes is therefore responsible for nearly all cases of human foodborne listeriosis worldwide. This is why regulations focus almost exclusively on this species.
Source: Springer, Veterinary Research, 2025; PMC, review on the taxonomy of the genus Listeria, 2020
How do you monitor Listeria monocytogenes in the production environment?
Environmental monitoring relies on regular sampling of surfaces and equipment, generally organized according to a zone system: surfaces in direct contact with the product, adjacent surfaces, floors and drains, then peripheral areas such as changing rooms. The most critical points are packaging areas located after heat treatment, as well as wet, cold areas, drains, and conveyors. This approach, sometimes called “seek and destroy,” makes it possible to detect a contamination niche before it reaches the finished product. It is now considered the most effective control lever against Listeria in the food industry.
Source: FDA Draft Guidance; PMC, Novel Approaches to Environmental Monitoring and Control of Listeria monocytogenes, 2022.
Finished-product control or environmental monitoring: which should you prioritize for Listeria?
Finished-product control has a major limitation: it comes too late to prevent a contaminated batch from reaching the market, and it provides no information on the source of the contamination. Environmental monitoring, on the other hand, makes it possible to detect a Listeria niche in the plant before it recontaminates a product, making it a preventive rather than curative tool. But neither approach on its own covers the full risk: it’s their combination, tailored to the production environment, the products manufactured, and the areas identified as sensitive, that offers the strongest level of control. A well-built environmental monitoring plan can reduce how often finished-product checks are needed, without ever eliminating them entirely, as a cross-check. This is also the spirit of the 2026 European regulatory reinforcement, which requires evidence of control built on several types of data, not a single type of check.
Source: FDA Draft Guidance; Regulation (EU) 2024/2895.
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