Scientific advances benefiting food safety
Raman spectroscopy coupled with isotope labelling: a revolution in microbiological diagnostics
Two methods are currently available for identifying pathogenic bacteria in food. However, both have limitations: agar culture media take several days to yield a result, while PCR methods are quick but can sometimes lack sensitivity when faced with very small quantities of bacteria.
To address these limitations, our laboratory has developed, in partnership with the French Alternative Energies and Atomic Energy Commission (CEA), an innovative approach based on Raman microspectroscopy coupled with isotopic labelling. In practical terms, food or environmental samples are prepared so that bacterial cells can be analysed individually, without the need for prior culturing. The cells are then examined under a microscope and analysed using a laser. The interaction between the laser and the molecules in the cell produces a specific spectral signature, a veritable "chemical fingerprint" that can be used to identify the bacterial species in the sample. This technology has several major advantages. In particular, it enables pathogenic bacteria to be detected without the need for prior culturing, even when they are present in very small quantities. It can also tell them apart from other bacteria in the sample and determine whether they are alive, dormant or dead: something that is difficult to achieve using conventional methods. Raman spectroscopy combined with isotope labelling therefore offers a fast and reliable method, reducing the risk of false positives and false negatives.
A patent application has been filed for part of this innovation. It could ultimately lead to the development of smart systems capable of automatically screening for microbiological contamination before food products are placed on the market.
Thomas Brauge, Scientific Project Leader and Head of the Bacteriology Team within the Aquatic Food Safety Unit at ANSES's Laboratory for Food Safety, Boulogne-sur-Mer site.
Supporting vaccination against Salmonella on laying hen farms
Salmonella is responsible for over a third of confirmed foodborne illness outbreaks in France. Eggs and egg products are implicated in nearly half of these outbreaks.
To protect consumers, the Ministerial Order of 27 February 2023 authorised the use of live attenuated vaccines against Salmonella on laying hen farms. This change was designed to strengthen measures to combat Salmonella in the poultry sector, but has nevertheless raised an important point: how can a vaccine strain, posing no risk to consumers, be distinguished from a wild strain capable of causing foodborne infections?
This distinction is crucial: if a pathogenic wild strain is detected, the affected eggs cannot be sold, and health measures – which may include culling the flock – must be implemented.
ANSES's National Reference Laboratory (NRL) for Salmonella has been helping approved laboratories deploy methods for distinguishing between vaccine strains and “wild” strains of Salmonella, mainly by organising inter-laboratory tests for assessing these methods and ensuring the reliability of the analyses carried out.
Laetitia Bonifait, Head of the National Reference Laboratory for Salmonella and Avian Salmonellosis, Unit for Hygiene and Quality of Poultry and Pork Products, ANSES's Ploufragan-Plouzané-Niort Laboratory.
New tests ensuring better management of the risk associated with Listeria in ready-to-eat foods
The bacterium Listeria monocytogenes causes listeriosis, a rare but potentially serious disease that is the second leading cause of death from foodborne illness in France.
Listeria monocytogenes is able to multiply under a variety of physico-chemical conditions, including at refrigerated temperatures, unlike other bacteria. For this reason, it is covered by specific regulations in certain ready-to-eat foods such as delicatessen meats or cheeses that are kept refrigerated.
Based on a risk assessment, if the bacterium is found in a food, this product is considered compliant provided that the concentration remains below 100 bacteria per gram throughout the product’s shelf life, up to its use-by date. Above this threshold, it is regarded as dangerous to consumers.
The European regulations, which have been in force since 2005, were revised in 2024 to strengthen studies on the shelf lives of foods and the requirements concerning health checks carried out by food business operators. For foods considered to pose a risk, the text specifies how operators must demonstrate that the products they place on the market are completely free from contamination, or how any low levels of contamination will not exceed this threshold of 100 bacteria per gram up to the use-by date.
For these studies, "growth tests" are conducted by laboratories recognised by the Ministry of Agriculture. They can simulate the growth of Listeria in food and, if contamination is detected, they can predict the level it will reach during the product’s shelf life. This French network is the only one of its kind in Europe and operates under the technical supervision of the National Reference Laboratory for Listeria monocytogenes. At the European level, the European Union Reference Laboratory for Listeria monocytogenes provides essential scientific and technical support for harmonising approaches based on close cooperation between operators, laboratories and health authorities. Both of these reference mandates are held by ANSES and coordinated by the Laboratory for Food Safety.
Corinne Danan, Head of the Salmonella and Listeria Unit at the Maisons-Alfort Laboratory for Food Safety, and Head of the National Reference Laboratory for Listeria monocytogenes.
Bacillus cereus: Franco-Belgian cooperation to overcome a health crisis
Since 2012, our Laboratory for Food Safety has been studying the bacterium Bacillus cereus and its toxins, particularly cereulide, which causes food poisoning. In late 2025, suspicions of Europe-wide contamination of infant formula with this toxin led to major efforts by our scientific teams. During this period, our laboratory was the only one in France capable of detecting the presence of cereulide in food, after seven countries (Austria, Belgium, Denmark, Spain, France, Luxembourg and the United Kingdom) reported cases of infants experiencing gastrointestinal symptoms following the consumption of infant formula. However, the available method could only confirm the presence of the toxin, without being able to measure its precise concentration when levels were low. In response to this health emergency, we forged a close collaboration with our Belgian partner Sciensano. The suspect samples were therefore analysed by their laboratory to precisely assess the level of contamination in the products.
Following this crisis, our laboratory continued developing and improving its analytical methodology to be able to quantify cereulide in food and achieve values below the health thresholds recommended by EFSA.
Moreover, since this crisis, manufacturers are now required to monitor the toxin cereulide, as well as the bacterium, which was not the case previously. Discussions are currently taking place at European level and within Member States to determine whether the regulations should be amended to include a criterion for this hazard.
Jacques-Antoine Hennekinne, Head of the Staphylococcus, Bacillus and Clostridium Unit, and Deputy Scientific Director of the Maisons-Alfort Laboratory for Food Safety.