Evaluation of antimicrobials residues in farmed gilthead seabream (Sparus aurata) after administration through medicated feed

Abstract

The use of antimicrobials in aquaculture is a well-known fact and merits the focus of the scientific community. In the present study, five drugs (oxytetracycline, sulfadiazine, trimethoprim, oxolinic acid and flumequine) were selected to assess their retention in muscle tissues from gilthead seabream (Sparus aurata). Fish were placed in 150 L tanks at 18 °C, and fed for 7 days with experimental diets containing two concentrations of each antimicrobial (ranging from 5.51 to 131.16 mg kg−1). Edible tissues were then analyzed through a validated multi-class quantification method (UHPLC-MS/MS). The results indicate that sulfadiazine concentrations were the highest immediately after the feeding period and decreased towards day 3. Flumequine was only detected on the first day with concentrations below the MRL. Both trimethoprim and oxolinic acid concentrations were below the MRLs 3 days after the feeding period was over (oxolinic acid was not detected in muscle samples at day 14 for prophylaxis and day 28 for both treatments). Oxytetracycline residues in muscle tissues were the highest through time, with concentrations above the MRL for 7 days (Cday7 of 111.2 and 157.2 μg kg−1 for both dosages). Results suggest that these antimicrobials can be present in gilthead seabream muscle samples for longer periods than previously reported, when realistic conditions are tested. With the exception of oxytetracycline, concentrations were below the MRLs established 3 days after the feeding trial was over meaning that adverse effects related to human consumption are not likely. Nevertheless, allergic reactions or resistance to antimicrobials can be developed if low concentrations of such compounds are ingested on a frequent basis, as is the case of the Mediterranean diet.