TERATOGENIC AND DEVELOPMENTAL EFFECTS OF ENROFLOXACIN IN EMBRYOS OF XENOPUS LAEVIS AND OF BRACHIDANIO RERIO

Enrofloxacin (EFX) is an antibacterial, belonging to the fluoroquinolones group, widely used in veterinary medicine, in particular for avian mass treatments. The main metabolite of enrofloxacin, ciprofloxacin (CPX, antimicrobial used in human medicine) is still characterized by a strong biological activity. The occurrence of these compounds in superficial waters has been proved by several studies and, although the common concentrations of these pharmaceuticals in freshwaters are in the order of hundred of nanograms per liter[1], peaks of tens milligrams per liter have also been occasionally found [2]. The aim of this study was to assess the teratogenic and developmental effects of EFX and his main metabolite CPX in two model organisms representative of the freshwater compartment: the frog Xenopus laevi and the fish Brachidanio rerio. Tests were performed following the FETAX (Frog Embryo Assay Xenopus, ASTM, 1998) and FET (Fish Embryo Toxicity Test, OECD, 2012) guidelines [3;4], with minor modifications. In both organisms no developmental or teratogenic effects were observed when they were exposed to the limit concentration of 100 mg/L of CPX. A significative reduction of tail movements frequency was instead observed in B.rerio embryos exposed to 100 mg/L of EFX. The same compound showed teratogenicity (optic and thoracic edemas) in X.laevis at concentrations of 50 mg/L and higher. To our knowledge, teratogenic effects of EFX have not been reported yet. While the tested effective concentration are far higher than those usually detected in the freshwater compartment, a possible risk for aquatic organisms cannot be excluded, the different sensitivity of the various species and the occasional peak concentrations of the compound considered.