Escherichia coli (E.coli) and salmonellosis bacteria, known to regularly cause food poisoning, have been responsible for massive food recalls for several weeks. In question, Buitoni pizzas (Nestlé group) and Kinder chocolates (Ferrero). In recent days, two children have died and dozens of others have fallen seriously ill after consuming the former. Kinder chocolates are suspected of being at the center of an epidemic of salmonellosis in Europe, which affected children a few days before Easter.
François-Xavier Weill is the head of the National Reference Center at the Institut Pasteur. This structure records cases of Escherichia coli and salmonellosis infections, and studies epidemics in humans. He returns for L’Express to these recent cases of food infections.
L’Express: Where do salmonella and E.coli bacteria come from?
Francois-Xavier Weill: Salmonella are generally bacteria that are found seasonally, rather in summer. This can be explained due to the change in behavior of people who change their eating habits a little, but also due to the rise in temperatures which favors the multiplication of bacteria.
This bacterium is found in the digestive tracts of animals, so there is a very large reservoir among farm animals and it is through these animals that contamination often comes. Raw meat, or foods derived from dairy products, such as raw milk cheese, are classic vectors. It can also be found in the water if, for example, cows contaminate groundwater.
Is it surprising to observe a concomitance of salmonella and E. coli?
The similarity in time of these two epidemics due to different germs is not really surprising since those caused by salmonella are relatively frequent in our country. What is really unusual here is the nature of the contaminated foods, both manufactured by two large food companies and widely distributed.
Are these outbreaks common?
Cases of infection with Shigatoxin-producing E. coli (these are specific E. coli and are responsible for serious infections linked to Buitoni) are generally quite rare. In recent years there have been about 160 cases of serious infections per year. The last episode, which saw 75 cases emerge in two months, is therefore quite exceptional. Above all, what is new is the food vector: we knew the risks of E. coli in raw milk cheeses and undercooked ground beef, but this is the first time it has been found in pizza dough. This could be due to the flour used, but this is an element that has never been observed in E. coli contaminations in France.
Then this wave of contamination is not trivial because it is linked to a food prepared on a large scale, nearly 200,000 pizzas prepared per day, whereas usually we find this bacterium rather in small batches such as cheeses artisanal products, whose use-by date is relatively short. This time we are on a product with a very long consumption date, which necessarily lengthens the possibilities of contamination.
Epidemics due to salmonella are very frequent, we have about 10,000 strains of confirmed cases per year, but we have seen for several years that these epidemics are falling significantly, in 20 years, they have fallen by half thanks to the systematic controls carried out in particular in laying hen farms. In 1994, a large salmonellosis epidemic with more than 220,000 cases linked to industrial ice cream had been observed in the United States. Today, we no longer see these large epidemics because we also know how to detect them earlier. epidemics.
How does this detection happen?
Sequencing technologies, which make it possible to determine the genetic strain of a bacterium or a virus, have improved enormously in recent years, and this now makes it possible to quickly identify the beginnings of epidemics. With sequencing, we can follow the appearance of new strains in real time, for example if we identify two identical strains from two patients who do not live under the same roof, we can say that they have eaten a food in common , and therefore follow the trail of this contaminated food.
We now have the tools to identify the start of epidemics. Salmonella found in Kinder chocolates represent around twenty cases in recent weeks. With old techniques, we could not have identified them. It is the sensitivity of this sequencing technique that allows us today to see precisely which strain is emerging. Thanks to this, we are better prepared than ten years ago, we can detect smaller and smaller episodes. And in the end, the goal is always the same: identify the product, remove it from sale, and issue a reminder for those that have already been sold.
What risks do these two bacteria represent?
The pathology observed most frequently with salmonella is febrile gastroenteritis. It happens soon after consuming the food, and the first symptoms appear between 12 and 72 hours. These are stomach aches, diarrhea, fever and possibly vomiting, but it is a self-limiting illness in healthy people. In very young children, but also the elderly, immunocompromised people and pregnant women, there may be a complication with the passage of the bacteria in the blood, which may require hospitalization.
E. coli bacteria, especially those that produce Shigatoxin, are far more dangerous. The symptoms are felt three to ten days after the contaminated meal in the form of often bloody diarrhoea. But in 10% of cases one week after this digestive episode, it can give rise to a syndrome of serious renal insufficiency (called haemolytic and uraemic syndrome) in particular in young children. The bacterium then causes vascular complications due to blood clots formed by this toxin. It can affect many organs, such as the kidney, brain, and heart. In young children, these serious kidney failures can have long-term consequences in nearly 70% of cases.
Why does the E.coli bacteria particularly affect children?
For the moment, it is an observation that we make and we have few explanations. We find cases at the extreme ages of life and it is often linked to the maturity of the immune system of these people. Young children are necessarily more sensitive to bacteria than adults whose immune system is more mature, more trained in the face of bacteria.
So, how to protect against it?
By washing your hands first. But if an item is contaminated, the consumer can still reduce the risk. By thoroughly cooking minced beef and avoiding soft raw milk cheeses in children under 5 years of age. But also by maintaining the cold chain for all raw egg products, for example, and by ensuring that raw products remain cool. If a food is cooked, there is no longer any risk, but what can also be avoided is cross-contamination, that is to say contaminating a food eaten raw (style tomatoes in salad ) by utensils (cutting board) having been in contact with raw meat… By respecting this, the risk is reduced, even if the product is contaminated from the outset by some pathogenic bacteria.