Presentation:
Increased rates of bacterial sexually transmitted infections (STIs) are reported among men who have sex with men (MSM), particularly among those using HIV pre-exposure prophylaxis (PrEP). Interventions to reduce the incidence of STIs are needed. In the field of STI prevention using doxycycline on-demand post-exposure prophylaxis (PEPdoxy), we are witnessing significant advances. Three large-scale randomized clinical trials (ANRS Ipergay, ANRS Doxyvac trial, DoxyPEP) have demonstrated a reduction of more than two-thirds in the incidence of bacterial STIs among MSM, notably for Chlamydiae trachomatis (CT) and Treponema pallidum (TP) infections, thanks to PEPdoxy. However, efficacy against Neisseria gonorrhoeae (GC) varies according to tetracycline resistance rates within populations, with Europe showing higher resistance rates than the US. This approach raises two major concerns: (i) the potential emergence of antimicrobial resistance, mainly to tetracycline, in pathogens responsible for STIs, as already observed for GC, which could worsen, or a new acquisition of resistance for CT and TP which has never been described, and (ii) the impact of doxy-PEP on the composition of the various microbiota and the pathogens present in these flora, in particular for Escherichia coli and Staphylococcus aureus. This presentation will give an overview of the available data on the impact of doxy-PEP strategies on the microbiota and the molecular mechanism conferring resistance. These studies on the microbiome and antimicrobial resistance surveillance for bacterial STIs should be continued over time to fully assess the impact of this strategy.