Objectives

The working hypothesis of the PharmOneHealth project is that the co-occurrence of chemical and microbiological contaminations could induce profound modifications in the organization of aquatic biofilms, including the replacement (species sorting) of certain endogenous species by opportunistic forms, including versatile pathogens such as those from the ESKAPE group or Achromobacter xylosoxidans. An association between pathogenic bacteria and pharmaceuticals has been previously observed in hospital effluents, suggesting, among other things, an association with nutrients that may promote at least transient colonization of pathogenic bacteria in receiving environments. The persistence of emission sources of these contaminants could lead to an enrichment of opportunistic pathogenic species that may serve as shuttles in inter-species genetic transfers (plasmids, integrons, genomic islands) within aquatic biofilms, thereby promoting the dissemination and amplification of virulence genes. The accumulation of pharmaceutical substances (anti-inflammatories, analgesics, beta-blockers, antidepressants, antibiotics) in biofilms could increase the importance of these different enrichment processes, thereby resulting, at the scale of microbial communities as a whole, in an increase in tolerance to this type of chemical pressure, in accordance with the PICT concept.

In this context, the project proposes to combine experimental approaches (in laboratory artificial channels) with in situ approaches (conducted in two rivers located respectively in rural areas, Mercier, and urban areas, Tillet, whose chemical pressures - pharmaceuticals, metals, pesticides, etc. - have already been characterized in previous projects) in order to specifically address the following challenges:

C1) Study, under controlled and in situ conditions, the bioaccumulation kinetics of pharmaceutical substances used in human and animal health in periphytic biofilms as well as their contamination levels in surface sediments and waters in order to better characterize the contamination of environments and define the exposure levels of microbial communities present in these two aquatic compartments;

C2) Determine in situ the co-occurrence between these pharmaceutical substances, pathogenic microorganisms, and the abundances and expression of virulence and ARG genes. A culture-based approach will also be developed to determine phenotypes and resistance mechanisms, and subsequently for transcriptomic studies on resistant isolates and comparison with clinical strains;

C3) Determine, under controlled conditions, influence of exposure levels (concentration and duration) of model substances (an antibiotic from the sulfonamide family, sulfamethoxazole; another from the fluoroquinolone family, ofloxacin; and a non-steroidal anti-inflammatory drug, diclofenac), alone or in mixtures, on the kinetics of species reassortment, acquisition of tolerance at the scale of microbial communities, and gains and losses of virulence and ARG genes, as well as the evolution of the resistance phenotype of a microbial genus.

C4) Test in situ, in rivers with contrasting physico-chemical properties, the relevance of the developed approaches (chemical - bioaccumulation measurement, ecotoxicological - PICT, molecular - DNA microarrays and metatranscriptomics, and electrochemical - measurement of enzymatic activities) with a view to using them as tools for the biomonitoring of aquatic environments in a context of chemical and microbiological contamination.