Influence of time-dependent sampling on the plasma metabolome and exposome of fish collected from an effluent-dependent pond

Interactions of erythromycin and an antibiotic mixture with the gut microbiome of juvenile rainbow trout

Erythromycin (ERY) is a commonly used antibiotic found in wastewater effluents and the environment globally. Due to the bioactivity by which they kill and prevent bacterial growth, ERY and other antibiotics may have significant unwanted impacts on the gut microbiome of fishes. The overall objective of this project was to assess effects on the gut microbiome in response to exposure to ERY alone or in a mixture with other common antibiotics, which was accomplished in two experiments. The objectives of experiment 1 as a pilot study were to understand uptake and depuration of ERY in juvenile rainbow trout (RBT) over a 7-d exposure to three concentrations of ERY followed by a 7-d depuration period. Furthermore, throughout the study changes in gut microbiome were assessed. In experiment 2, an identical experimental design was used to assess the effects of a mixture of antibiotics containing, in addition to ERY, 100 μg/g each of ampicillin, metronidazole, and ciprofloxacin. In that study, three matrices were analyzed, with gut collected for 16S rRNA metabarcoding, blood plasma for non-targeted metabolomics, and brain tissue for mRNA-seq analysis. ERY was relatively quickly depurated from fish and gut microbiome dysbiosis was observed at 7 d after exposure, with a slight recovery after the 7-d depuration period. A greater number of plasma metabolites was dysregulated at 14 d compared to 7 d revealing distinct temporal dynamics compared to gut microbiome dysbiosis. Furthermore, several transformation products of antibiotics and biomarker metabolites were observed in plasma due to antibiotic exposure. The transcriptome of the brain was only slightly altered due to antibiotic exposure. Results of these studies will help inform aquaculture practitioners and risk assessors when assessing the potential impacts of antibiotics present in fish feed and the environment, with implications for host health.

Metabolomic study on ostracods exposed to environmentally relevant concentrations of five pharmaceuticals selected via a novel approach

Pharmaceuticals (PhACs) are increasingly detected in aquatic ecosystems, yet their effects on biota remain largely unknown. The environmentally relevant concentrations of many PhACs may not result in individual-level responses, like mortality or growth inhibition, traditional toxicity endpoints. However, this doesn't imply the absence of negative effects on biota. Metabolomics offers a more sensitive approach, detecting responses at molecular and cellular levels and providing mechanistic understanding of adverse effects. We evaluated bioaccumulation and metabolic alterations in a benthic ostracod, Heterocypris incongruens, exposed to a mixture of five PhACs (carbamazepine, tiapride, tolperisone, propranolol and amlodipine) at environmentally relevant concentrations for 7 days using liquid chromatography coupled with mass spectrometry. The selection of PhACs was based, among other factors, on risk quotient values determined using toxicological data available in the literature and concentrations of PhACs quantified in our previous research in the sediments of the Odra River estuary. This represents a novel approach to PhACs selection for metabolomic studies that considers strictly quantitative data. Amlodipine and tolperisone exhibited the highest bioaccumulation. Significant impacts were observed in Alanine, aspartate and glutamate metabolism, Starch and sucrose metabolism, Arginine biosynthesis, Histidine metabolism, Tryptophan metabolism, Glycerophospholipid metabolism, and Glutathione metabolism pathways. Most of the below-individual-level responses were likely nonspecific and related to dysregulation in energy metabolism and oxidative stress response. Additionally, some pharmaceutical-specific responses were also observed. Therefore, untargeted metabolomics can be used to detect metabolic changes resulting from environmentally relevant concentrations of PhACs in aquatic ecosystems and to understand their underlying mechanism.

The effect of warming and seasonality on bioaccumulation of selected pharmaceuticals in freshwater invertebrates

Multiple human-induced environmental stressors significantly threaten global biodiversity and ecosystem functioning. Climate warming and chemical pollution are two widespread stressors whose impact on freshwaters is likely to increase. However, little is known about the combined effects of warming on the bioaccumulation of environmentally relevant mixtures of emerging contaminants, such as pharmaceutically active compounds (PhACs) in freshwater biota. This study investigated the bioaccumulation of a mixture of 15 selected PhACs at environmentally relevant concentrations in common freshwater macroinvertebrate taxa, exposed to ambient temperatures and warming (+4 °C) during the warm and cold seasons in two outdoor mesocosm experiments. Nine PhACs (carbamazepine, cetirizine, clarithromycin, clindamycin, fexofenadine, telmisartan, trimethoprim, valsartan and venlafaxine) were dissipated faster in the warm season experiment than in the cold season experiment, while lamotrigine showed the opposite trend. The most bioaccumulated PhACs in macroinvertebrates were tramadol, carbamazepine, telmisartan, venlafaxine, citalopram and cetirizine. The bioaccumulation was taxon, season and temperature dependent, but differences could not be fully explained by the different water stability of the PhACs and their partitioning between water and leaf litter. The highest water-based bioaccumulation factors were found in Asellus and Planorbarius. Moreover, the bioaccumulation of some PhACs increased with warming in Planorbarius, suggesting that it could be used as a sentinel taxon in environmental studies of the effects of climate warming on PhAC bioaccumulation.