Fluoroquinolone Residues in Fish Collected from Farms and Retail Stores in Stara Zagora Region, Bulgaria

Background: Fluoroquinolones are among various antibiotic groups used in livestock husbandry. The aim of this screening study was to evaluate the presence of fluoroquinolone residues in fish samples of Stara Zagora region, Bulgaria. Methods: A total of 69 samples from freshwater, marine, and anadromous fish were collected randomly from fish farms and retail stores in Stara Zagora region, Bulgaria. Fluoroquinolone residues were determined using Enzyme-Linked Immunosorbent Assay method. Data were statistically processed using STATISTICA 10.0 software. Results: Fluoroquinolones were detected in 44.3% of freshwater and 42.9% of marine fish samples, with no significant difference (p>0.05). Their concentrations varied from 1.03 to 271.73 μg/kg for common carp, 1.43 to 12.63 μg/kg for rainbow trout, 1.17 to 1.94 μg/kg for silver carp, 1.00 to 1.82 μg/kg for rudd and 1.27 to 2.15 μg/kg for striped catfish. Among marine fish, fluoroquinolone positive samples were found in European sprat (1.68 μg/kg), Longtail southern cod (1.30 μg/kg), and European hake (1.83 μg/kg). Conclusion: High levels of fluoroquinolones were found in some fish samples of Stara Zagora region, Bulgaria. Regular monitoring of antibiotic residues is too necessary in fish distributed in this region.