Determination of diffusion coefficients in agarose and polyacrylamide gels for 112 organic chemicals for passive sampling by organic Diffusive Gradients in Thin films (o-DGT)

International audienceThe diffusive gradient in thin film technique was recently adapted to organic compounds. The diffusional coefficient (D) is a key parameter needed to calculate the time-weighted average concentration. In this study, two methods are used for D measurement in two gels (agarose and polyacrylamide): the diffusion cell method (D-cell) and the slice stacking method (D-stack). Thus, D were discussed and compared for 112 organic compounds, including pesticides, hormones, and pharmaceuticals. D-stack tends to be higher than D-cell. It could be explained by the presence of a non-negligible diffusive boundary layer thickness in diffusion cell. Consequently, the use of sampling rates (R-S) should be more adequate to determine water concentration, for a given bulk flow velocity. D-stack also corresponds to the diffusion in gel only, allowing the determination of the maximal R-S, and would be considered as a reference value that can be adjusted to in situ conditions, by applying the appropriate DBL thickness. The range and variability of D values found in the literature and obtained in this work were discussed. Relationships between D and compound physicochemical properties (molecular mass, log Dow, polar surface area, van der Waals volume) were investigated. We did not find clear and robust correlation between D and any single physicochemical property, for the set of compounds tested

In situ translocation experiment to assess the adaptation and resilience of periphytic communities to pharmaceutical substances using a PICT approach

International audienceNumerous studies have demonstrated the worldwide occurrence of pharmaceutical contamination in aquatic environments, in which they can affect microbial periphytic communities. Recent monitoring in a small river located in Lake Bourget watershed (Tillet River, Savoie, France) showed the accumulation of pharmaceuticals in its downtream urban section. In this context, we sought to (i) assess if this chronic exposure to contamination can cause an increase in the tolerance of microbial communities to a set of pharmaceutical substances (‘pollution induced community tolerance’ concept, PICT) and (ii) study the tolerance dynamics (tolerance acquisition, or loss) according to exposure level changes.To reach these objectives, we carried out an in situ translocation study in the Tillet River, considering an upstream (reference) and a downstream (contaminated) site. After a 4-week growth phase in each site, periphytic biofilms were transferred between the sites to simulate, during 6 weeks, a restoration (down- to upstream) or deterioration (up- to downstream) of the chemical water quality. Water contamination was monitored using polar organic chemical integrative samplers (POCIS), and biofilm community tolerance was assessed using a PICT approach. Acute toxicity tests were performed on biofilms sampled every 2 weeks, using 7 pharmaceuticals tested individually (ofloxacin, atenolol, diclofenac, paracetamol, erythromycin, sulfamethoxazole, sulfamethazine) and measuring the following biological activities: β-glucosidase, photosynthesis, or growth. Our results confirmed the expected increase in pharmaceutical concentrations in surface water from up- to downstream. In parallel, an increased biofilm tolerance mainly towards diclofenac and atenolol was observed at the downstream station, from the toxicity tests on photosynthesis. The translocation approach also revealed an increase of tolerance levels in communities transferred downstream, and a decrease of tolerance levels in communities transferred upstream, suggesting resilience processes. This work demonstrates the relevance of the PICT approach for in situ diagnosis of the impact of pharmaceuticals on natural microbial communities

L'approche PICT pour évaluer in situ l'adaptation et la résilience de biofilms périphytiques aux substances pharmaceutiques : expérience de translocation dans un cours d'eau contaminé

International audienceLa contamination des milieux aquatiques par les substances pharmaceutiques impacte les communautés microbiennes périphytiques exposées. Cela peut se traduire, entre autres, par une modification de la diversité microbienne associée à une augmentation de la tolérance de la communauté à ces substances, conformément au concept PICT (pollution induced community tolerance). Cependant, les liens de causalité entre les niveaux d’exposition aux substances pharmaceutiques et les niveaux de tolérance à leur toxicité restent à établir. Pour tester la pertinence de l’approche PICT pour évaluer in situ l’adaptation et la résilience de biofilms périphytiques aux substances pharmaceutiques, nous avons mené une expérience de translocation sur une rivière présentant un gradient de contamination. Du périphyton a été déplacé entre l’amont (référence) et l’aval (contaminé) pour simuler, durant 6 semaines, une dégradation (vers l’aval) ou une restauration (vers l’amont) de la qualité chimique de l’eau (caractérisée à l’aide d’échantillonneurs passifs, POCIS). Sept substances modèles ont été considérées pour l’approche PICT et la diversité des communautés périphytiques a été appréhendée par métabarcoding (ADNr16S et 23S, rbcL).Dans la station aval contaminée, nous avons observé une forte tolérance des communautés phototrophes au diclofénac et à l’aténolol. Pour ces deux substances, la translocation a permis d’observer progressivement une adaptation (tolérance accrue) ou au contraire une résilience (perte de tolérance) de ces communautés suite à leur déplacement vers l’aval et vers l’amont, respectivement. L’approche PICT est donc prometteuse pour évaluer in situ l’adaptation ou la résilience microbienne aux substances pharmaceutiques et contribuer au diagnostic de leur impact environnemental

Diagnostic des impacts écotoxicologiques des substances pharmaceutiques en cours d'eau : translocation de communautés microbiennes périphytiques et mesures de tolérance (PICT)

National audienc

Effect of a karst system (France) on extended spectrum beta-lactamase (ESBL)-producing Escherichia coli

International audienceKarst aquifers are an important water resource worldwide particularly exposed to anthropogenic pollution, including antibiotic-resistance. The release of antibiotic-resistant bacterial pathogens in the environment is a major public health challenge worldwide. In this One Health study, we aimed to determine the effect of karst on antibiotic-resistant bacteria. For this purpose, we determined the concentrations of extended-spectrum β-lactamases-producing Escherichia coli (ESBL-Ec) for 92 weeks in a rural karst hydrosystem providing drinking water. ESBL-Ec isolates (n = 130) were sequenced by whole genome sequencing. We analysed the isolates at different levels of granularity, i.e., phylogroup, sequence type, presence of antibiotic-resistance genes, mutations conferring antibiotic-resistance, and virulence genes. The ESBL-Ec concentrations were spatially and temporally heterogeneous in the studied karst hydrosystem. ESBL-Ec isolates survived in the karst and their concentrations were mostly explained by the hydrodynamic of the hydrosystem. We demonstrate that the studied karst has no filtration effect on ESBL-Ec, either quantitatively (i.e., in the ESBL-Ec concentrations) or qualitatively (i.e., in the genetic characteristics of ESBL-Ec isolates)

Bioassay-based profiling of steroid- and dioxin-like activities in French river waters using grab and integrative sampling

Effect-based methods (EBM) are relevant tools to monitor chemical quality of aquatic systems as they provide integrative assessment of contamination components and inform on hazard associated with complex mixtures. In the frame of a French national program aiming at demonstrating the operational performance of passive sampling to monitor priority chemicals in surface waters, we applied a panel of in vitro bioassays to investigate 1) the occurrence of steroid- and dioxin- /PAH-like activities, 2) their distribution in the water column using grab sampling and integrative passive sampling. In addition, we looked into the relevance of in vitro estrogenicity in the water as compared to established trigger values and in vivo assessment in zebrafish. Twenty surface water sites of different anthropogenic pressures were studied. For each of them, both grab (dissolved phase and particulate matter) and integrative sampling (POCIS and Silicone Rubber membranes) were performed over a 15 days period and organic extract of each sample was analyzed with the bioassays. In vitro toxicity profiles in grab water organic extracts showed contrasted contamination patterns depending on the time of sampling (T0 and T15) and the studied sites. Estrogenic and PAH-like activities were the most occurent activities, while glucocorticoidic and anti-androgenic ones were detected at specific sites. No androgenic activity was detected. PAH-like activity was associated with both the dissolved and particulate matter phases while endocrine activities were only found in the dissolved phase. At some sites, in vitro estradiol-equivalents were found above the generic trigger value considering environmental risk (0.4 ng E2Eq/L). For 7 sites out of the 10 tested in vivo, activities were coherent with those predicted by in vitro bioassays. The present study highlights the relevance of combining a set of effect-based tools and smart sampling to monitor site-specific contamination of surface water chemical quality and the partitioning of measured activities in the water column. Our approach further includes in vivo mechanism-based assays, which enhances the toxicological relevance of the assessment. Comparison of our data with established trigger values for some activities will be discussed. Finally, ongoing chemical analyses of more than 100 priority substances, including estrogenic hormones, will allow the determination of their contribution to the biological activities detected

Bioassay-based profiling of steroid- and dioxin-like activities in French river waters using grab and integrative sampling

Effect-based methods (EBM) are relevant tools to monitor chemical quality of aquatic systems as they provide integrative assessment of contamination components and inform on hazard associated with complex mixtures. In the frame of a French national program aiming at demonstrating the operational performance of passive sampling to monitor priority chemicals in surface waters, we applied a panel of in vitro bioassays to investigate 1) the occurrence of steroid- and dioxin- /PAH-like activities, 2) their distribution in the water column using grab sampling and integrative passive sampling. In addition, we looked into the relevance of in vitro estrogenicity in the water as compared to established trigger values and in vivo assessment in zebrafish. Twenty surface water sites of different anthropogenic pressures were studied. For each of them, both grab (dissolved phase and particulate matter) and integrative sampling (POCIS and Silicone Rubber membranes) were performed over a 15 days period and organic extract of each sample was analyzed with the bioassays. In vitro toxicity profiles in grab water organic extracts showed contrasted contamination patterns depending on the time of sampling (T0 and T15) and the studied sites. Estrogenic and PAH-like activities were the most occurent activities, while glucocorticoidic and anti-androgenic ones were detected at specific sites. No androgenic activity was detected. PAH-like activity was associated with both the dissolved and particulate matter phases while endocrine activities were only found in the dissolved phase. At some sites, in vitro estradiol-equivalents were found above the generic trigger value considering environmental risk (0.4 ng E2Eq/L). For 7 sites out of the 10 tested in vivo, activities were coherent with those predicted by in vitro bioassays. The present study highlights the relevance of combining a set of effect-based tools and smart sampling to monitor site-specific contamination of surface water chemical quality and the partitioning of measured activities in the water column. Our approach further includes in vivo mechanism-based assays, which enhances the toxicological relevance of the assessment. Comparison of our data with established trigger values for some activities will be discussed. Finally, ongoing chemical analyses of more than 100 priority substances, including estrogenic hormones, will allow the determination of their contribution to the biological activities detected

Biosurveillance d'activités stéroïdiennes et dioxin-like dans les eaux de surface françaises par une approche couplant bioessais et échantillonnage ponctuel et passif

International audienc