Acute toxicity evaluation of four antibacterials with Daphnia magna

Oxytetracycline (OTC), tylosin (TYL), sulfadimethoxine (SDM) and sulfamethazine (SMZ) are largely employed for mass treatments in food animals and so prone to contaminate the environment. According to the EMEA guidance document on Environmental Impact Assessment for veterinary drugs, a Predicted No Effect Concentration in water should be derived from the acute toxicity test in Daphnia magna. Using Daphtoxkit\uae (compliant with OECD Guideline 202) their toxicity on Daphnia magna was evaluated. Results shows a low sensitivity to OTC and SDM, confirms a moderate sensitivity to TYL (EC50=1012 mg/L) and highlights the particular sensitivity to SMZ (EC50=112 mg/L). This is of interest because SMZ is one of the most widely used sulfonamide and has been detected in soil and in wells