Experimental assessment of antibiotic resistance in a Biofilm - Grazer system

Antimicrobial resistance (AMR) is a growing global health threat, with environmental compartments such as soil, water, and biofilms playing key roles in the dissemination and persistence of resistance genes. In this study, we explored the dynamics of AMR within a controlled Biofilm-Grazer system using Xenopus laevis larvae and biofilms A and B collected from two distinct rivers in Occitanie, France (collected respectively upstream from the large city of Toulouse and downstream from a wastewater treatment plant). The objective of the study was to investigate bacterial interactions between gut microbiota and biofilms, as well as the modulation of ARG (Antibiotic Resistance Gene) abundance and diversity over a 12-day period. Results showed a decrease of resistome in Xenopus gut microbiota feeding on both biofilms compared to feeding on commercial feed. In addition, an increase of resistome of Biofilm B compared to Biofilm A was observed. Procruste analysis and Pearson's correlations revealed a link between bacterial communities changes and ARG abundances in biofilms. Rhodobacter genus could be an ARG host shared between compartments. Furthermore, bacterial immigration predominantly occurred from the gut to the biofilms, with both biofilms acting as reservoirs for ARGs. Notably, Biofilm B, collected from a more polluted river, demonstrated a higher relative abundance of aac3-IVa resistance genes in the gut microbiota of larvae, compared to Biofilm A and a higher immigration rate from biofilm to gut. These findings highlight the complexity of interactions between biofilm communities and the gut microbiota, which may influence AMR dissemination.