Genotoxic responses of juvenile tilapia (Oreochromis niloticus) exposed to florfenicol and oxytetracycline

Florfenicol (FLC) and oxytetracycline (OTC) are the two most commonly used antibiotics for bacterial treatment in fish farming in Brazil, and because of their intensive use, the potential harmful effects on aquatic organisms are of great concern. This study evaluated the effects of environmental concentrations of FLC and OTC on the genetic material of juvenile tilapia (Oreochromis niloticus) erythrocytes by using the comet assay and the occurrence of micronuclei (MN) and other erythrocytic nuclear abnormalities (ENAs) after exposure to 96 hour. The comet assay showed that fish erythrocytes exhibited significantly higher DNA damage after exposure to environmental concentrations of FLC and OTC. Although MN was not observed, ENAs were significantly higher after exposure to FLC, indicating that ENAs are a better biomarker for FLC than MN. The results showed that environmental concentrations of FLC and OTC were genotoxic to erythrocytes of O. niloticus; however, future studies on DNA damage recovery are needed.