The second cause of food-borne illnesses in Europe, salmonellosis is most often manifested by acute gastroenteritis. However, it can more seriously affect certain susceptible populations who are then prescribed antibiotic therapy. What if there was an alternative to taking antibiotics in the treatment of salmonellosis? This is what suggest recent work according to which intestinal bacteria might block the growth and virulence of certain salmonellae.
Salmonellosis and antibiotic resistance
Second cause of food-borne illnesses in Europe, salmonellosis is most often manifested by acute gastroenteritis with abdominal pain, diarrhoea, nausea and sometimes severe vomiting. It is actually an infection with salmonella (bacteria belonging to the genus Salmonella) capable of crossing the intestinal barrier.
To know ! Most salmonellae are housed in the intestines of vertebrate animals and are transmitted to humans via contaminated food.
They can nevertheless affect more seriously or even fatally certain susceptible populations. such as the elderly, infants, pregnant women or immunocompromised people who are then prescribed antibiotic therapy. Not to mention that one of the strains of salmonella (Salmonella Heidelberg) is particularly resistant to antibiotics. Therefore, it would be wise to find an alternative to antibiotics to avoid this problem of resistance.
Recent work by Inserm scientists goes in this direction. They suggest that intestinal bacteria might block the growth and virulence of certain salmonellae.
Towards an alternative to antibiotics in the treatment of salmonellosis?
To carry out their work, the scientists relied on previous studies that had demonstrated that an intestinal bacterium called Bacteroides fragilis reduced the ability to Salmonella Heidelberg to cross the intestinal barrier in mice. The interest of this intestinal bacterium being proven, it remained to decipher the mechanisms at the origin of the anti-infective effect observed.
To know ! Bacteroides fragilis designates a bacterium of the Bacteroidota family (the most abundant in the intestine). Beneficial for health, it helps maintain the balance of the intestinal microbiota.
For this, it was necessary to identify and characterize the compounds secreted by the bacteria Bacteroides fragilis following culture in the laboratory. And it is actually the culture supernatant that interested the researchers. Very rich, they split it to separate the different compounds.
To know ! The culture supernatant designates the liquid medium in which the bacteria multiply in vitro and where the metabolites which they secrete into their environment are found.
Of the six fractions collected and then brought into contact with Salmonella Heidelberg, two were able to block the growth of pathogenic Salmonella. After administration to infected mice, the scientists observed that these same fractions had reduced the intestinal inflammatory reaction and reduced the ability of the pathogen to cross the intestinal barrier. You must know that Bacteroides fragilis and its metabolites do not attack salmonella itself, but rather how it interacts with host cells. This strategy makes it possible to better regulate the virulence of salmonella.
Biliary metabolites: an alternative to antibiotic therapy?
The next step consisted in identifying the metabolites, including cholic acid and deoxycholic acid, naturally present in bile juices. However, it would seem that these two compounds alone have no demonstrated antibacterial action in vivo. Hence the researchers’ desire to discover the nature of other potentially active molecules. The identification of such compounds might thus make it possible to develop a new alternative to antibiotic therapy. Next step for researchers? To know if these metabolites are active once morest other bacterial species pathogenic for humans or animals. Case to follow!
Déborah L., Doctor of Pharmacy
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