a toxic trio of bacteria

Salmonella, E. Coli and listeria. These three categories of bacteria, all mentioned in the news, are the cause of many food poisonings, sometimes fatal, and have many points in common.

Here is a presentation of these three bacteria which are however far from being the cause of all food infections, often caused by a virus as in many gastroenteritis.

– Salmonella, main risk –

Salmonellosis, of which several dozen cases have been detected in Europe with a possible link to Kinder chocolates, is the leading cause of death from food poisoning.

This disease, the cause of several hundred deaths each year in France, is caused by salmonella, a large family of bacteria also behind typhoid fever.

Named after the American veterinarian who discovered them, Daniel Elmer Salmon, these bacteria mostly come from the digestive tract of animals.

A wide variety of foods, eaten raw, undercooked or contaminated after cooking, can be the source of contamination: meat, eggs or raw milk…

More rarely, contamination can result from the consumption of fruits or vegetables. It can also come from powdered milk.

Symptoms of salmonellosis appear on average after one to three days of incubation. They are most often those of sometimes acute gastroenteritis: diarrhea and abdominal cramps, slight fever, even vomiting.

But the infection can, in some cases, be dangerous, even fatal: the youngest or the elderly can indeed find themselves in severe dehydration under the effect of diarrhea.

Complications are also possible, such as sepsis or meningitis. For severe forms, antibiotic treatment is indicated.

– Listeria, second danger –

After salmonellosis, listeriosis is the second cause of death by food poisoning with, in France, a few dozen deaths per year.

It is caused by the bacterium Listeria Monocytogenes, recently found in several cheeses produced by a subsidiary of the Lactalis group, although no cases of infection have been reported.

In its so-called “invasive” form, listeriosis is particularly deadly: around a quarter of patients die from it, for example because of neurological complications such as meningitis.

Incubation generally lasts one or two weeks, but can go up to almost three months, and pregnant women are particularly at risk, with twenty times more risk of developing this infection than the rest of the population.

Like salmonellosis, listeriosis is treated with antibiotics. And like salmonella, listeria is eliminated by cooking and is therefore found in raw or undercooked foods: meats, dairy products, fresh vegetables and fruits…

But it also has its specificities. While the cold slows the development of salmonella, this is not the case for listeria which can reproduce in large numbers in a refrigerator.

Listeriosis is therefore often linked to “foods that can be stored for a long time in refrigerated conditions”, summarizes the World Health Organization (WHO).

– E. coli, difficult to treat –

Highlighted in the news by a recent outbreak of cases in France, linked to Buitoni pizzas (Nestlé), Escherichia Coli is the cause of significantly fewer deaths than salmonella and listeria.

This is a large family of bacteria, many of which are present in the human digestive system and even help it function.

But some varieties can cause poisoning. Again, heat kills them and a whole range of raw or undercooked foods can be blamed, from certain meats to sprouted seeds, as in the worst epidemic observed to date in Europe in 2011.

In rare cases, these intoxications, which appear three to four days after ingestion, can degenerate into “hemolytic and uremic syndrome” (HUS), with in particular renal failure.

Like salmonellosis, it is especially the elderly and children who are at risk.

But, unlike salmonellosis and listeriosis, antibiotics should not be used, as they may on the contrary make things worse. Severe E. Coli infection is therefore particularly difficult to treat.


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