STABLY

The emergence of Staphylococcus aureus multi-resistant strains is a major problem in human and animal health. The ability of these bacteria to be resistant to antibiotics is closely linked to the resistance-carrying plasmids present in S. aureus strains. These mobile genetic elements play a major role in microbial ecology and evolution. Under certain conditions, they represent an adaptive advantage for the bacterium, but their replication constitutes a metabolic burden for the host cell. Yet, even without selection pressure, plasmids are maintained in cells and are widespread in nature. The paradox of plasmid persistence is an evolutionary dilemma that remains unsolved. The majority of studies on this phenomenon have been carried out in Gram-negative bacteria based on in vitro evolution experiments, which do not reproduce the "real life" of the plasmid in its host cell. Although plasmids play a central role in the dissemination of antibiotic resistance in S. aureus, their dissemination mechanisms, adaptive cost and persistence are poorly documented in this species and in Gram-positive bacteria in general. In the STABLY project, we propose to decipher the mechanisms involved in the persistence of these mobile genetic elements in non-selective environments of increasing complexity, as well as in sub-inhibitory conditions of antibiotics corresponding to the different environments encountered by S. aureus (healthy carriage, hospitals, livestock...). The understanding of the phenomena involved in the maintenance of these resistance-carrying plasmids will allow a better evaluation of the risk of emergence of new resistances and will open avenues to prevent their dissemination.