Occurrence of tetracyclines, sulfonamides, fluoroquinolones and florfenicol in farmed rainbow trout in Iran

This study was carried out to determine the occurrence of tetracyclines, sulfonamides, fluoroquinolones and florfenicol residues in rainbow trout muscle samples (n = 138) obtained from Iranian trout farms. Concentrations of the antibiotics were determined using competitive enzyme-linked immunosorbent assay method. At measurable levels, 63.1%, 16.7%, 19.6% and 40.6% of the samples contained the residues of tetracyclines, sulfonamides, fluoroquinolones and florfenicol, respectively. The detected range of concentrations for positive samples was 1.43–101.4 µg/kg for tetracyclines, 4.03–90.4 µg/kg for sulfonamides, 6.75–99.8 µg/kg for fluoroquinolones and 0.11–172.6 µg/kg for florfenicol. The residues of the antibiotics in trout samples did not exceed the maximum residue levels recommended by the Institute of Standards and Industrial Research of Iran. However, the high occurrence of tetracyclines and florfenicol in the samples is alarming and could be a potential hazard for public health. Further investigations should be performed to determine the residues of antibiotics in other farmed fish species in Iran.