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What if Crohn’s disease is caused by bacteria?

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While the origins of Crohn’s disease are still unknown, researchers have recently claimed to follow a serious lead. According to them, the invasion of a particular E. coli could be the source of the problem.

A potentially pathogenic E. coli

Let us first remember that Crohn’s disease is a form of chronic inflammatory disease of the intestine. It affects around 200,000 people, with a particularly high prevalence in the Western world. Its origin is still little known. However, scientists agree that the appearance of the first symptoms is a result of genetic and environmental factors. In addition, inflammation of the digestive tract is linked to an overactive immune system.

What if Crohn’s disease was actually caused by bacteria? A team of American and Canadian researchers detail this hypothesis in a study published in the journal Nature communications April 1, 2021. According to scientists, the inflammatory background of Crohn’s disease promotes the invasion of an E. coli present in 70 to 80% of patients.

To understand the work of researchers, we must first differentiate betweenCommensal E. coli of the’E. coli Invasive Adherent (ECAI). The former is one of the common bacteria in a healthy gut microbiota while the latter is potentially pathogenic. However, researchers say they have identified several metabolic genes at the heart of overexpression during inflammation. Not only do these genes allow ECAI to survive, but they also promote its multiplication.

Credit: Flickr / NIAID

Nothing certain yet

Among the genes in question, let us quote that encoding the type IV secretion system (T4SS). Scientists in the study used a mouse model that mimicked Crohn’s disease. In vivo, bacteria lacking T4SS cannot colonize the intestine. On the other hand, the presence of this same system allows the ECAIs to adhere to the intestinal mucosa. Above all, these E. coli then form a biofilm protecting them from antibiotics. In passing, let’s mention the fact that T4SS is made up of several proteins forming a complex around a kind of hole (the pilus, or pili in the plural). These pili allow bacteria to exchange DNA as well as to secrete proteins in an external environment. Now they also participate in bacterial adhesion as well as the production of biofilms.

It is therefore no coincidence that these ECAIs protected by their biofilm make the resolution of the predominant inflammatory state in Crohn’s disease very complicated. However, the question arises as to whether or not these colibacilli are the causative agent of the disease. For researchers, they are a potential disease trigger Crohn’s, but more research needs to be done to confirm this.


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