Antimicrobial Residues in a Key Cerrado River: Distribution, Persistence, and Effects on Zebrafish Embryo-Larval...

The current study aimed to quantify the antimicrobials amoxicillin (AMX), cefazolin (CFZ), chloramphenicol (CHL), metronidazole (MTZ), and sulfamethoxazole (SX) in effluents and surface water of an important Cerrado river, calculate their half-lives, and analyze their ecotoxicity following single and combined exposures. Four sampling surveys were carried out to identify the antimicrobials employing HPLC-MS/MS. Surface water was collected from the river's spring to the mouth, and effluent samples were taken at a sewage treatment plant (STP). The pySiRC tool was used to predict the half-life of antimicrobials in aqueous media under •OH-attack. Ecotoxicity was assessed using a zebrafish embryo-larval toxicity assay at environmentally relevant concentrations of the detected antimicrobials. Just MTZ (0.1 to 45.5 ng L^-1) and SX (0.1 to 502.7 ng L^-1) were detected in this study. The persistence of MTZ and SX in the aqueous environment was estimated at 14 to 139 days and 9 to 88 days, respectively. The single exposure to MTZ induced cardiotoxicity and changes in the swim bladder and tail curvature. MTZ and SX induced sensory and physiological morphometric changes compared to the control. MTZ, alone or combined with SX, affected the larvae's behavior. Our findings contribute to the understanding of the presence, persistence, and ecotoxicity of antimicrobials in aquatic environments.