Abstract
This study aimed to investigate the occurrence of antibiotic residues in rainbow trout muscle samples (n = 74) obtained from Iranian trout farms. The levels of the antibiotics were determined by in-house validated HPLC methods. Oxytetracycline, tetracycline, enrofloxacin, ciprofloxacin, and florfenicol residues were detected in 6.76%, 37.8%, 31.1%, 10.8%, and 14.9% of the samples, respectively; while chlortetracycline was not detected. The detected range of concentrations for positive samples was 8.94–81.2 μg/kg for oxytetracycline, 7.99–98.4 μg/kg for tetracycline, 6.75–87.4 μg/kg for enrofloxacin, 5.83–11.5 μg/kg for ciprofloxacin, and 49.9–313.6 μg/kg for florfenicol. None of the samples exceeded the maximum residue levels (MRLs) established by the Institute of Standards and Industrial Research of Iran. The co-occurrence of antibiotics was detected in 40.5% of the analyzed samples. The frequency of co-occurrence of enrofloxacin-tetracycline was the highest (16.2%). Despite the fact that concentrations of the analyzed antibiotics in trout samples did not exceed the MRLs, their co-occurrence in such a level could be a serious public health problem.