Exposure of benthic microbial communities to pharmaceuticals and resulting adaptation including tolerance, biodegradation and antibiotic resistance: advances and challenges

International audienceSince the early 1920’s, pharmaceuticals, including antibiotics, have been massively producedand consumed for the benefit of both human and animal health. Pharmaceuticals residues havethen reached the aquatic environment through diffuse and point (wastewater) sources. Amongthe pharmaceutical residues, the ubiquitous presence of antibiotics could exert a selectivepressure on microbial communities leading to the acquisition and dissemination of antibioticresistance in the environment.We present here the synthesis of recent research projects (e.g. PANDORE, Antibio-tools,Antibiotox, PharmaTox...) investigating the dissemination of pharmaceuticals, includingantibiotics, in the different aquatic compartments (surface water, periphyton, sediment) and itsimpact on periphyton and sediment microbial communities. These projects mainly focused onantibiotic resistance genes (ARG), community tolerance to pharmaceuticals (PICT) and antibioticbiodegradation capacity by combining field studies on different lake and lotic ecosystem (e.g.rivers Arve, Tillet and Le Clain; lake Geneva) and experimental approaches in microcosms. Ourresults highlight the ubiquitous presence of pharmaceuticals in the studied ecosystems and thespecific distribution of pharmaceuticals in the different investigated compartments. The fieldsurveys generated an important antibiotic resistance database including relative abundance ofARG and genetic mobile elements as well as functional measurements of microbial tolerance(PICT approach) to selected pharmaceuticals and biodegradation potential of sulfonamideantibiotics. Antibiotic resistance was found to be positively correlated with the presence ofwastewater treatment plant effluents, but we confirm that the links between exposure levels,i.e. antibiotics concentrations, and antibiotic resistance must be considered in all ecosystemcomplexity. Further analyses are currently on-going to better take into account potentialconfounding factors.These research projects generated advances in our knowledge on pharmaceuticals andantibiotic resistance dissemination within the aquatic environment but also reveal the currentchallenges to better understand the drivers of antibiotic resistance in such complexenvironments