In vitro toxicity of antimicrobials on RTG-2 and RTL-W1 fish cell lines

This study proposed a battery of endpoints based on in vitro fish cell lines. Two fish cell lines and four toxicity endpoints are considered. The tetracycline (TC), oxytetracycline (OTC), sulfachlorpyridazine (SCP), and septrin(?) (ST) were selected as model antimicrobials and chlorpyrifos as positive control. EROD was induced by septrin(?) (formulation containing sulfamethoxazole and trimethoprim) at concentrations higher than 20mg/L, but inhibited by tetracycline, oxytetracycline and chlorpyrifos. Dose dependent inhibition responses were observed for β-galactosidase (β-Gal) activity in cells exposed to septrin(?), tetracycline or oxytetracycline. The EROD EC50s ranged between 2.29×10(-2)mg/L (chlorpyrifos) and 167.63mg/L (tetracycline). The β-Gal EC50s ranged between 22.1 (septrin(?)) and 84.59mg/L (tetracycline). Data suggest that in vitro testing using a battery of endpoints can be a cost-effective solution for screening the toxicity of antimicrobials on fish. The absence of in vitro effects at concentrations well above those expected/measured in the environment may replace the need for conducting acute lethality tests on fish.