The bacteria present in the intestine play an essential role in the maintenance of good health. These bacteria are also a formidable weapon in the fight against certain serious intestinal infections, caused by dangerous bacteria present in cattle feces, such as “hamburger disease”.
Our gut contains approximately ten trillion (10,000,000,000,000) bacteria per gram of content, the highest concentration of microbes of any living world. Is it dangerous? Not at all ! Under normal conditions, this intestinal flora does not pose any danger, quite the contrary: it contains a wide variety of species which live in symbiosis with us and which actively participate in the maintenance of normal physiological functions, both at the level of the intestine and of the body in general.
Bacteria of the Bifidobacterium genus, commonly called bifidobacteria, are without a doubt the components of the intestinal flora that have the most positive impact on health. Already present only a few hours after birth, these bacteria have the particularity of transforming substances rich in sugar (food fibers for example) into lactic and acetic acids. This slight acidification of the intestine prevents the proliferation of several pathogenic micro-organisms and thus makes it possible to maintain a balance in the composition of the intestinal flora. This balance is not only crucial for digestive functions: several studies indicate that intestinal bacteria are also involved in the proper functioning of the immune system and could even play a role in brain development and the acquisition of certain character traits. !.
Hamburger disease: possibly deadly
In addition to these vital functions, recent data indicate that bifidobacteria also have a protective function against certain pathogenic bacteria, in particular the dangerous Escherichia coli O157:H7. This pathogen, which generally comes from bovine excrement, can establish itself in the intestine where it produces a powerful toxin (shiga-toxin) which causes intense abdominal cramps and hemorrhagic diarrhoea. In the most serious cases, this toxin causes a dramatic drop in the quantity of blood platelets (thrombocytopenia), destruction of red blood cells and loss of kidney function. Hemolytic uraemic syndrome, better known as “hamburger disease”, develops, a very serious disease that can lead to death, especially in young children and the elderly.
Good bacteria to fight bad bacteria
A team of Japanese researchers has shown that intestinal bifodobacteria can counteract the damage caused by this bacterium. They observed that in animals lacking bifidobacteria, the pathogen is extremely virulent and causes rapid death, just days after infection. On the other hand, the situation is very different in animals whose intestine contains these bifidobacteria: the pathogen does not cause any deaths, even more than two weeks after infection. Subsequent analyzes suggest that this protection is caused by the ability of bifidobacteria to metabolize carbohydrates into acetic acid. Indeed, the researchers noted that this acid prevented the toxins secreted by the pathogenic bacteria from crossing the intestinal mucosa and reaching the blood, thus protecting the animal from infection.
Intestinal bacteria are therefore not simple “passengers” who accompany us throughout our lives, but real partners who actively participate in maintaining our health. In this sense, probiotics and facto-fermented foods represent a simple and effective way to increase the quantity of these bacteria in the intestine and thus take advantage of their multiple beneficial properties.
Heijtz RD et al. Normal gut microbiota modulates brain development and behavior. Proc Natl Acad Sci USA; 108: 3047-3052.
Fukuda S et al. Bifidobacteria can protect from enteropathogenic infection through production of acetate. Nature; 469: 543-547.
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