Turbot Scophthalmus maximus , an important aquaculture species in China, currently suffers from epizootic diseases because of high density aquaculture. Enrofl oxacin has been used to treat various systemic bacterial fi sh infections. However, studies concerning the pharmacokinetics of enrofl oxacin in turbot are limited. In this study, the pharmacokinetics of enrofl oxacin and its metabolite ciprofl oxacin, were investigated in the turbot following intravenous and oral administration at 10 mg enrofl oxacin/kg body weight, at 16°C and 10°C water temperatures. The concentrations of enrofl oxacin and ciprofl oxacin in the main tissues (plasma, muscle, liver and kidney) were detected by HPLC. The results show that the plasma concentration-time data for enrofl oxacin were best described as a two-compartment open model after intravenous and oral administration. Three pharmacokinetic equations were established between the concentrations and temperatures. The kinetic profi le of enrofl oxacin was temperature dependent. The absorption half-life of enrofl oxacin was 1.99 h and 2.17 h after oral administration, whereas the elimination half-life of the drug was 98.63 h and 136.59 h at 16°C and 10°C, respectively. The peak concentration of enrofl oxacin in plasma and tissues was higher at 16°C than that at 10°C, and the peak plasma concentration time in the liver was the shortest at both temperatures among those of other tissues. The plasma C max /MIC ratio varied between 11.08 and 5 540.00 at 16°C; and between 7.92 and 3 960.00 at 10°C. The AUC/MIC ratio was 467.82-280 690.00 at 16°C, and 359.48-215 690.00 at 10°C. These ratios indicate that it is possible to obtain therapeutic effi cacy. Very low levels of ciprofl oxacin were detected. The AUC ratios of ciprofl oxacin and enrofl oxacin in plasma suggest that plasma ciprofl oxacin might play a minor role in enrofl oxacin treatment for turbot.

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This study aimed to quantify the environmental fate of antimicrobials applied in Fenneropenaeus chinensis aquaculture production in China and to assess their potential risks for surrounding aquatic ecosystems, for the promotion of antimicrobial resistance in target and non-target bacteria and for consumers eating shrimp products that contain antimicrobial residues. For this, we first used the results of an environmental monitoring study performed with the antimicrobial sulfamethazine to parameterize and calibrate the ERA-AQUA model, a mass balance model suited to perform risk assessments of veterinary medicines applied in aquaculture ponds. Next, a scenario representing F. chinensis production in China was built and used to perform risk assessments for 21 antimicrobials which are regulated for aquaculture in China. Results of the model calibration showed a good correspondence between the predicted and the measured sulfamethazine concentrations, with differences within an order of magnitude. Results of the ecological risk assessment showed that four antimicrobials (levofloxacin, sarafloxacin, ampicillin, sulfadiazine) are expected to have adverse effects on primary producers, while no short-term risks were predicted for invertebrates and fish exposed to farm wastewater effluents containing antimicrobial residues. Half of the evaluated antimicrobials showed potential to contribute to antimicrobial resistance in bacteria exposed to pond water and farm effluents. A withdrawal period of three weeks is recommended for antimicrobials applied via oral administration to F. chinensis in order to comply with the current national and international toxicological food safety standards. The results of this study indicate the need to improve the current regulatory framework for the registration of aquaculture antimicrobials in China and suggest compounds that should be targeted in future aquaculture risk assessments and environmental monitoring studies.

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