Exposure of benthic microbial communities to pharmaceuticals and resulting adaptation including tolerance, biodegradation and antibiotic resistance: advances and challenges
Résumé
Since the early 1920’s, pharmaceuticals, including antibiotics, have been massively produced
and consumed for the benefit of both human and animal health. Pharmaceuticals residues have
then reached the aquatic environment through diffuse and point (wastewater) sources. Among
the pharmaceutical residues, the ubiquitous presence of antibiotics could exert a selective
pressure on microbial communities leading to the acquisition and dissemination of antibiotic
resistance in the environment.
We present here the synthesis of recent research projects (e.g. PANDORE, Antibio-tools,
Antibiotox, PharmaTox...) investigating the dissemination of pharmaceuticals, including
antibiotics, in the different aquatic compartments (surface water, periphyton, sediment) and its
impact on periphyton and sediment microbial communities. These projects mainly focused on
antibiotic resistance genes (ARG), community tolerance to pharmaceuticals (PICT) and antibiotic
biodegradation 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. Our
results highlight the ubiquitous presence of pharmaceuticals in the studied ecosystems and the
specific distribution of pharmaceuticals in the different investigated compartments. The field
surveys generated an important antibiotic resistance database including relative abundance of
ARG and genetic mobile elements as well as functional measurements of microbial tolerance
(PICT approach) to selected pharmaceuticals and biodegradation potential of sulfonamide
antibiotics. Antibiotic resistance was found to be positively correlated with the presence of
wastewater treatment plant effluents, but we confirm that the links between exposure levels,
i.e. antibiotics concentrations, and antibiotic resistance must be considered in all ecosystem
complexity. Further analyses are currently on-going to better take into account potential
confounding factors.
These research projects generated advances in our knowledge on pharmaceuticals and
antibiotic resistance dissemination within the aquatic environment but also reveal the current
challenges to better understand the drivers of antibiotic resistance in such complex
environments.