In our study, we were surprised to find that treatment with amoxicillin and clavulanic acid (Augmentin), a treatment regularly prescribed by doctors, also reduced the fungal population in the intestine in an in vivo mouse model.

The study of the effect of these antibiotics on the fungal and bacterial intestinal microbiota allowed us to show that there was a massive modification of the bacterial microbiota and in particular an increase in amoxicillin-resistant populations, including enterobacteria. In vitro analyses of strains isolated from these microbiotas after treatment with this cocktail of antibiotics allowed us to identify a strain of bacteria partly responsible for the fall in the fungal population: Enterobacter hormaechei. Indeed, E. hormaechei is able in vitro in co-culture and in vivo after gavage in mice to decrease the amount of fungi. To date, the mechanisms explaining these effects are not completely understood. We have been able to show a slight competition effect around the nutrients useful to the fungi to grow but not strong enough to explain the observed effect. On the other hand, we have also demonstrated a clear physical interaction between the cells of the fungi and the bacteria after specific co-culture of this bacterium using scanning microscopy images.

This study allowed us to show that the effect of a treatment with antibiotics has different effects on the fungal population depending on the type of antibiotic. We have also identified a new bacterial strain capable of having a negative effect on the growth of fungi in a complex context of the intestinal microbiota. The continuation of our research work will allow us to elucidate the mechanisms of action of this bacterium on fungi and to progress in our understanding of the interaction between these 2 microbiotas.

Article: https://doi.org/10.1186/s40168-023-01516-y

Video: https://youtu.be/UqlwxRJx5jE