A French agency has studied the main bacterial hazards associated with raw milk cheeses and other products made from raw milk.

The French Agency for Food, Environmental and Occupational Health and Safety (ANSES) identified the types of unpasteurized milk cheeses on which to target efforts.

In France, over the past decade, 34 percent, 37 percent and 60 percent of outbreaks of salmonellosis, listeriosis and E. coli  infections have been linked to raw milk cheeses.

The focus fell on soft cheeses with a surface mold such as Camembert, Brie and Crottin and short-ripened uncooked pressed cheeses like Morbier, Reblochon and Saint-Nectaire as well as soft washed-rind cheeses such as Munster and Maroilles.

In total, 46 hazard food pairs were judged as relevant by experts. They covered E. coli, Salmonella, Listeria monocytogenes, Staphylococcus aureus and histamine in cheese, butter and cream.

Supply chain approach
ANSES received the request for the study from the Directorate General for Food (DGAL) in 2019. The aim was to assess the main sources of contamination and ways to control these risks.

Methods to control microbiological risks in the main dairy sectors of cattle, sheep and goat from the rearing stage to consumption, were studied by the agency.

At farm level, measures included good animal husbandry and hygiene practices. The ANSES study said ongoing efforts in terms of hygiene during milking and the management of mastitis should be continued.

During production, risk control was also very high. The agency recommended continuing to implement good hygiene practices and to carry out self-checks to best anticipate any risk of an outbreak.

For consumers, to avoid a foodborne infection, it is essential to comply with information on the packaging or that given by the seller concerning the temperature at which raw milk cheese should be stored in the refrigerator and its use-by date.

ANSES recommends that pregnant women, immunocompromised individuals, people over the age of 65 and young children should not eat raw milk cheeses, except for hard pressed cheeses such as Gruyère and Comté.

Related outbreaks
Among 50 Salmonella outbreaks with a confirmed food source between 2008 and 2018, 18 were caused by raw milk cheeses. Five of them sickened more than 100 people.

Six of 10 E. coli outbreaks recorded by Santé publique France between 2004 and 2019 were because of raw milk cheese. These products were behind 14 of 37 Listeria outbreaks that affected 103 people between 2012 and 2018.

Types of cheeses most often linked to outbreaks were soft and uncooked pressed cheeses and were made from cow’s milk.

Information from epidemiological investigations shows some incidents are because of a lack of hygiene control on the farm or during production. For others, the causes were not identified. This indicates that, even when good hygiene practices and control measures seem to be followed by operators, contamination can occur.

Laurent Guillier, who coordinated the expert appraisal, said levels of hygiene and risk control are now high on farms and self-checks at the processing stage are able to identify problematic batches.

“For several years now, we have been seeing a strong commitment on the part of the various raw milk cheese sectors to preventing microbiological risks. However, there is still a residual risk and it is important to identify new ways of optimizing the current control measures. For example, this could involve improving epidemiological investigations, identifying poor hygiene practices at an earlier stage, or communicating more with consumers.”

The work to classify raw milk cheeses was the first stage. Efforts are continuing to evaluate effectiveness of various health measures such as sorting milk at farm level and self-checks at the production stage. The next step will be to identify priority areas to further reduce microbiological risks.