HomeHealthSTEC in cheeses, in-depth analysis

STEC in cheeses, in-depth analysis

STECShiga-toxin producing Escherichia coli. The recent recall of a batch of sliced ​​scamorza offers an opportunity to learn more about this bacterium. (1)

The jambs of E. coli capable of producing Shiga-toxins they are among the most dangerous foodborne bacteria. Since they are capable of causing particularly severe and sometimes lethal clinical forms, especially in consumers most at risk (children and the elderly).

STEC, the bacterium and its consequences on consumer health 

The Escherichia coli STEC they are able to adhere firmly to the cells of the intestinal epithelium and to produce powerful toxins, the so-called toxins Shiga-like, precisely. Which enter the circulation and carry out their action on target cells far from the intestinal tract. Namely, the endothelial cells that line the vessels of the renal glomeruli and the small blood vessels of the colon. 

STEC infections they are therefore characterized by diarrheal episodes sometimes complicated by intestinal bleeding (hemorrhagic colitis). And in the most severe cases, from acute renal failure linked to dysfunction of the renal glomeruli. Real insufficiency is aggravated by concomitant haemolytic anemia and platelet deficiency, which concur to delineate the serious picture of the so-called Hemolytic-Uremic Syndrome (HUS). 

HUS and hemorrhagic colitis they can have a lethal outcome, or in any case cause serious pathologies such as chronic renal failure, with the possible need for dialysis treatment and the use of a kidney transplant. The severity of the disease leads the authorities responsible for the protection of public health to the utmost severity in cases of foodstuffs contaminated by STEC. 

STEC, dairy products and meats

Several animal species - the ruminantsi, in particular - house E. E. coli coli Shiga-toxin producers in the intestine without presenting any symptoms of disease. The animals in this case behave as 'asymptomatic carriers'. And their milk, or their meat, can enter the food chain if not subject to targeted analyzes. 

Cheeses, when subject to recall, are more dangerous, as they are foods that are not subject to heat treatment before consumption (food 'Ready-to-Eat'). Heat treatments above 70 ° C - such as pasteurization or boiling of milk and complete cooking of meat - are vice versa effective in destroying the jambs of E. E. coli coli producers of Shiga-toxins.

Contamination from STECof a cheese can therefore derive from the raw material (milk), but it can also occur downstream of the production process. This is the case of 'post-process' contamination, which can take place despite the following hygienic control procedures (supplier control, milk pasteurization, hygiene of the production process), therefore in spite of their apparent adequacy.

The 'post-process' contamination, in particular, it can be attributed to the colonization of equipment - in the industrial or distribution phase (e.g. portioning or packaging machines) - by microbial jambs capable of forming tough microbial films, commonly called 'biofilms', where the bacteria are produced by the action of disinfectants used in sanitation practices. The ability to form biofilms is indeed inherent in several bacteria, including E. E. coli coli producers of Shiga-toxins.

STEC, operators' responsibilities and corrective actions to be taken 

The food business operator (OSA)is primarily responsible for placing on the market foods that do not present a risk to the health of the consumer. (2) The responsibility of the operators downstream of the supply chain contributes to this responsibility, and in particular of the distributor.

The implementation of hygiene measures (GMP, GHP) and the capillarity of the analytical controls in the plant and in the distribution - including the identification of any niches colonized by biofilm-producing bacteria - are confirmed as essential to reduce the microbiological risk of food safety.

Foods contaminated by STEC- as prescribed by theGeneral Food Law'- must be classified as a serious risk to public health and therefore subjected to the most drastic corrective measures. (3) In implementation of the European rules in force, there are no tolerable microbial limits and the mere presence of STEC is sufficient, even at minimum levels, to trigger the alert on all potentially involved product lots.

Silvia Bonardi and Dario Dongo


(1) Recall of the F.lli Ponti Agricultural Company, 2,5 kg cheese product, production batch no. 06-28.8.18, reason for reporting the presence of E.Coli STEC. Notification 3.10.18, on the website of the Ministry of Health

(2) For further information on the subject, please refer to our free ebook 'Food safety, mandatory rules and voluntary standards', up https://www.greatitalianfoodtrade.it/libri/sicurezza-alimentare-regole-cogenti-e-norme-volontarie-il-nuovo-libro-di-dario-dongo. For updates on the evolution of the international reference standard, ISO 22000: 2018, see the article https://www.greatitalianfoodtrade.it/certificazioni/iso-22000-2018-lo-standard-aggiornato-per-la-sicurezza-alimentare

(3) See reg. CE 178/02, articles 14 and 19. Among the corrective actions to be taken, when the product at risk has already reached the level of distribution to the consumer isany other measure is unsuitable for guaranteeing public health', it is necessary to proceed with the public recall

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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. 

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Dario Dongo, lawyer and journalist, PhD in international food law, founder of WIISE (FARE - GIFT - Food Times) and Égalité.

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