Ecotoxicity of veterinary enrofloxacin and ciprofloxacin antibiotics on anuran amphibian larvae

The ecological risks posed by two beta-diketone antibiotics (DKAs, enrofloxacin, ENR and ciprofloxacin, CPX), characterized by their long persistence in aqueous environments and known deleterious effect on model organisms such as zebrafish were analysed using Rhinella arenarum larvae. Sublethal tests were conducted using environmentally relevant concentrations of both ENR and CPX (1-1000 mu g L-1) under standard laboratory conditions for 96 h. Biological endpoints and biomarkers evaluated were body size, shape, development and growth rates, and antioxidant enzymes (glutathione-S-transferase, GST; Catalase, CAT). Risk assessment was analysed based on ration quotients (RQ). The size and shape measurements of the larvae exposed to concentrations greater than 10 mu g L-1 of CPX were lower compared to controls (Dunnett post hoc p < 0.05) and presented signs of emaciation. Concentrations of 1000 mu g L-1 ofCPX induced GST activity, in contrast with inhibited GST and CAT of larvae exposed to ENR. Risk assessments indicated that concentrations greater than or equal to 10 mu g L-1 of CPX and ENR are ecotoxic for development, growth, detoxifying, and oxidative stress enzymes. It is suggested that additional risk assessments may provide evidence of bioaccumulation of CPX and ENR in tissues or organs of amphibian larvae by mesocosm sediment test conditions. Finally, intestinal microbiome studies should be considered to establish the mechanisms of action of both antibiotics. (C) 2017 Elsevier B.V. All rights reserved.