Listeria Is Not Rare. It Is Persistent.
What surveillance data really show
Recent surveillance analyses by EFSA highlight something that may seem contradictory at first: detection rates of Listeria monocytogenes in foods remain relatively low, while cases of listeriosis continue to rise steadily across Europe. This shows that the real issue is not how often the pathogen appears, but how consistently and persistently certain strains survive — mainly in ready-to-eat foods and products with a long shelf life. Simply put, Listeria does not need to appear often. It just needs to stay. “Listeria is not a problem because it appears often, but because it establishes itself and persists.” Listeria is not highly aggressive, but it is extremely adaptable. It can survive refrigeration, elevated salt levels and complex microbial ecosystems, taking advantage of small gaps in cleaning procedures, equipment design or production flow. Its strength is not speed, but endurance—and its ability to return.
What has changed in the regulatory approach
For years, risk management focused primarily on the final product. Absence in 25 g at production or on the market was considered a sufficient indicator of safety. This approach was based on the assumption that a product remains microbiologically stable throughout its shelf life. Today, we know this assumption is not always safe. Food microbiology is not static; it is dynamic and evolves over time. The European regulatory framework has not changed fundamentally. Regulation (EU) 2073/2005 remains the cornerstone of microbiological criteria. What has changed is how it is applied in practice. Shelf life is no longer treated merely as a commercial decision, but as a critical risk management tool. Food businesses are now required to demonstrate that, under reasonably foreseeable storage and distribution conditions, Listeria levels will not exceed acceptable limits by the end of the declared shelf life. When such evidence cannot be provided, applying the stricter criterion of absence in 25 g throughout the entire shelf life is not excessive—it is necessary.
Why shelf life is not just a number
In practice, this shift translates into the growing importance of shelf-life studies and challenge tests. These are not extreme scenarios, but tools that describe realistic product behaviour. If Listeria is present, how will it evolve over time? Will it remain stable, or will it grow—and under which conditions? Particular attention is required for products traditionally perceived as “safe,” such as white brined cheeses, ready-to-eat foods, and products packaged under vacuum or modified atmosphere. In these cases, the issue rarely lies in the formulation itself. It lies in microbiological behaviour over time—in subtle pH changes, interactions with background microflora, and temperature deviations during distribution.
When the source is not the product, but the environment
According to technical guidance and observations from the European Union Reference Laboratory for Listeria monocytogenes, many recurring detections are not due to repeated raw material contamination, but to established populations within the production environment. Wet areas, drains, conveyor lines, and hard-to-clean equipment can act as reservoirs, allowing the pathogen to re-emerge periodically. “The critical question is not whether Listeria was detected, but where it comes from—and why it keeps coming back.” In this context, conventional environmental monitoring alone is often insufficient. Strain-level analysis, such as whole genome sequencing (WGS), combined with integrated evaluation of product and environmental data, enables links between detections, sources, and recurring patterns. Tools such as Microbiome Mapping Studies (MMS) are increasingly part of the discussion, supporting more proactive control strategies.
What this means in practice for the food industry
Food safety today is not judged by whether a single inspection was passed. It is judged by whether a company can scientifically justify why it does not expect a problem tomorrow. Moving from compliance to prediction is not a luxury — it is a sign of industry maturity. At QACSFOOD, this approach is reflected in a combination of tools: product microbiological testing, shelf-life studies, challenge tests, strain analysis using whole genome sequencing (WGS), and targeted environmental mapping through microbiome mapping of the production area (MMS). The goal is not simply detection, but understanding risk — and preventing it before it becomes a problem for the product, the business, and ultimately the consumer.