'Malga' cheeses and other fresh or semi-fresh raw milk cheeses expose the most vulnerable consumers to the serious risk of contracting food poisoning with serious complications, due to contamination with the STEC pathogen (Shiga toxin-producing Escherichia coli).
1) Fresh raw milk cheeses, the STEC danger
The Chronicles Italian authorities recently report the case of a two-year-old girl, hospitalized since July 2023 at the Padua hospital due to a haemolytic-uremic syndrome caused by the consumption of an 'alpine' cheese produced with raw cow's milk. (1)
The cheese indicted was produced in an area of Trentino where a similar episode had already occurred in 2017 which had endangered the life of a four-year-old boy, also suffering from haemolytic-uremic syndrome which led him into a vegetative state. (2)
2) STEC, haemolytic uremic syndrome and other complications
STEC (Shiga toxin-producing Escherichia coli) is the acronym used to describe highly virulent strains of Escherichia coli which synthesize the dangerous Shiga toxins (3,4).
The pathogenic action of STEC, like that of other jambs of E. coli, first affects the intestine and manifests itself with symptoms of diarrhea in the few days following exposure to the microorganism. Complications - as in most pathogens, of a bacterial nature (e.g. Listeria monocytogenes) and viral (e.g. N. See notes 5,6) – are then linked to individual vulnerability. As:
– in several patients the symptoms of STEC infection are limited to the intestine and do not differ from other similar foodborne infections,
– in more fragile subjects, such as pre-school children and the elderly, however, Shiga toxins can cause vascular lesions in various organs such as the intestine, kidney and brain tissue. Thus causing, depending on the case, hemorrhagic colitis, renal failure and neurological lesions typical of hemolytic-uremic syndrome.
The haemolytic uremic syndrome it is a very serious condition, which involves dysfunctions of the kidney which tend to become chronic with possible, incurable neurological complications.
3) Risky dairy foods
Ruminants – cattle, sheep and goats – can host STEC bacteria in the intestine without therefore suffering their pathogenic action, and eliminate them with excrement. Adult ruminants can therefore act as a reservoir of STEC, in the absence of gastrointestinal symptoms, and be milked regularly or sent for slaughter without there being any need to investigate their health conditions further.
Raw milk it can be contaminated during the milking phase - through contact with the animal's faeces, often present on the skin of the udder - or in any case in the stable, due to the use of non-sanitized equipment or containers. STEC can also be inactivated with an appropriate heat treatment, pasteurization at +72°C for at least 15 seconds or at +63°C for at least 30 minutes. Consequentially:
– raw milk, fresh and semi-mature cheeses made from raw milk are at risk of STEC contamination. (7)
As regards cheeses, an adequate maturation process (not less than 60 days) creates an environment unfavorable to bacterial survival, including STEC, thanks to the fermentations of lactic bacteria which increase the acidity of the paste and to the salting which reduces the water available to microorganisms.
4) STEC risk-free foods
The 'STEC danger' does not exist for:
- raw milk which is boiled before consumption, as prescribed by the OM 10.12.2008,
- pasteurized or sterilized milk (where the temperature reaches +135°C),
- cheeses produced with pasteurized milk,
- mature hard cheeses, even if made from raw milk. The long seasoning, which often exceeds 12 months, associated with salting, hinders bacterial survival.
5) Recommendations to consumers
It is recommended to do not give raw milk not pasteurized or boiled, fresh and semi-fresh raw milk cheeses a children in preschool age, elderly and immunocompromised people.
6) Useful prohibitions
Industrial operators of the food sector have the duty to prevent, control and mitigate all possible food safety risks. Self-control – which integrates the GHPs (Good Hygienic Practices) with the HACCP system (Hazard Analysis on Critical Control Points) – must first consider the most serious dangers, such as the STEC and Listeria pathogens in animal products.
The Ministry of Health moreover - given the non-negligible recurrence, in Italy as at EU level, of drug infections and recalls of products contaminated by STEC (8) - it could consider the introduction of emergency measures such as the ban on the administration of raw milk cheeses to children preschoolers (6 years old), the elderly and other residents of assisted living facilities.
Silvia Bonardi and Dario Dongo
Footnotes
(1) Dafne Roat. 2-year-old girl in hospital since July, blamed on cheese from a mountain pasture: confirmation in tests. The little girl is serious. Corriere del Trentino (Il Corriere della Sera). 2.9.23
(2) Matthew Lunelli. 4-year-old girl in intensive care in Padua. Escherichia coli bacteria in contaminated cheeses. The previous one: six years ago a child in a coma. The Adige. 21.9.23
(3) Bonardi Silvia. “Pathogenic Escherichia coli”. In: Food hygiene and technologies. Ed. G. Colavita. Point Vétérinaire Italie publisher, Milan, 2023; pp. 121-126
(4) Silvia Bonardi, Dario Dongo. STEC in cheeses, in-depth analysis. GIFT (Great Italian Food Trade).
(5) Dario Dongo. Listeria, a dangerous pathogen out of control. GIFT (Great Italian Food Trade).
(6) Silvia Bonardi. Norovirus in seafood, how to protect yourself. GIFT (Great Italian Food Trade).
(7) Dos Santos Rosario AIL, da Silva Mutz Y, Castro VS, da Silva MCA, Conte-Junior CA, da Costa MP. Everybody loves cheese: crosslink between persistence and virulence of Shiga-toxin Escherichia coli. Critical Reviews in Food Science and Nutrition 2021;61(11):1877-1899. doi: 10.1080/10408398.2020.1767033.
(8) The RASFF 2022 report reports 26 cases of alerts for STEC out of the 199 alerts relating to microbiological risks on meat other than poultry, as well as the third place of STEC (after salmonella and listeria) on milk and dairy products. See paragraphs 5.3, 5.4 in the previous article Dario Dongo, Marta Strinati. RASFF 2022, EU food safety report. GIFT (Great Italian Food Trade).
Graduated in Veterinary Medicine and Specialist in Inspection of Food of Animal Origin and in Veterinary Public Health, she is Professor of Inspection and Control of Food of Animal Origin at the University of Parma.
Dario Dongo, lawyer and journalist, PhD in international food law, founder of WIISE (FARE - GIFT - Food Times) and Égalité.
