Listeria is a genus of bacteria comprising 27 species, among which Listeria monocytogenes is pathogenic to humans, causing listeriosis. Although listeriosis is relatively rare, it can lead to severe health issues, particularly in vulnerable populations such as the elderly, pregnant women, newborns, and immunocompromised individuals.
Understanding Listeria monocytogenes
Symptoms range from mild gastroenteritis to severe conditions like septicemia, meningitis, and spontaneous miscarriages. Listeria monocytogenes is notable for its ability to grow at low temperatures (as low as +2°C) and tolerate high salt concentrations, making it a persistent concern in refrigerated and processed foods.
Common sources of Listeria in food
Listeria monocytogenes is widespread in the environment, found in soil, water, and animal reservoirs. It can contaminate various food products, especially
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Smoked fish and meats (particularly beef and pork)
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Cheeses made from raw milk
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Raw and frozen vegetables
Contamination can occur during processing, especially if food is handled or sliced after cooking but before packaging. Cooking food above 65°C can kill Listeria monocytogenes, but recontamination remains a risk without proper hygiene practices.
Regulatory standards for Listeria monocytogenes in food*
In both the UK and EU, Listeria monocytogenes is subject to strict microbiological criteria under Regulation (EC) No 2073/2005. This regulation has been retained in UK law and applies to ready-to-eat (RTE) foods that can support the growth of Listeria monocytogenes.
Food business operators (FBOs) must ensure that these criteria are met throughout the entire product's shelf life. This is typically demonstrated through growth studies, predictive microbiology, or shelf-life testing, alongside implementation of environmental monitoring plans.
The EU has introduced an amendment, Regulation (EU) 2024/2895, requiring zero detection in 25g for all RTE foods unless scientific evidence proves the 100 cfu/g threshold will not be exceeded. This update applies from 1 July 2026 in the EU, but has not yet been adopted in Great Britain.
*Regulations are subject to change. Please consult the Food Standards Agency or relevant local authorities for the most up-to-date information. Eurofins food consultancy experts are also available to provide tailored support and horizon scanning.
Listeria testing methods
Eurofins network of laboratories offers accurate detection and enumeration of Listeria monocytogenes in a variety of food and feed matrices, and environmental swabs. Several testing methods are employed, based on the specific requirements
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Standard Methods: NF EN ISO 11290-1 (detection) and NF EN ISO 11290-2 (enumeration) providing results within 3 to 7 days**. ISO detection methods are sometimes required in certain export cases or for low-contamination matrices. Their strengths lie in their sensitivity and specificity.
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Chromogenic Methods: Validated alternatives offering results in 48 to 72 hours**. Their main advantages are sensitivity, specificity, and cost-effectiveness, making them well-suited for large and regular sample volumes.
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Immunological methods: Allow for automated analysis and eliminate the need for manual interpretation. Detection results can be obtained within 48 to 51 hours**. However, confirmation, which requires a bacterial culture step, takes longer.
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PCR Method: Rapid detection (18 to 28 hours**), certified for all food matrices and production environments. It is particularly well-suited for release testing and crisis management. Nevertheless, in cases of suspicion, confirmation takes 48 to 72 hours** due to the need for a bacterial culture step.
**Note: We are continuously developing new methodologies to meet evolving needs. For details on accreditation status and turnaround times for specialist microbiological testing, please contact your local Eurofins Food Testing UK laboratory as some services are delivered locally, while others may be delivered through our network of Eurofins Laboratories and Competence Centres.
Advanced analysis for contamination source tracking
In cases of contamination, Whole Genome Sequencing (WGS) can be utilised to determine the genetic relatedness of Listeria monocytogenes strains. This aids in tracing the contamination source and implementing targeted control measures.
Contact us for Listeria testing services
Ensuring the safety of your food products is paramount. Our network of accredited Eurofins laboratories offer comprehensive Listeria testing services, including rapid detection methods and expert consultancy.
For expert support with your listeria food safety needs, Contact us or call +44 (0) 845 604 6740.
