Elimination of chloramphenicol in rainbow trout receiving medicated feed.

Chloramphenicol muscle residue levels in rainbow trout were determined after oral administration of 84 μg kg-1d-1 of chloramphenicol for four days. Samples were taken one day before treatment and for 43 days after the treatment was over. Chloramphenicol was analysed using an in-house enzyme linked immunoassay (ELISA) validated against the criteria of the Commission Decision 2002/657/EC. Validation parameters confirmed that the method was appropriate for the detection of chloramphenicol at levels below the minimum required performance limit (MRPL) of 0.3 μg kg-1. The highest chloramphenicol levels were observed on the first day after the treatment had ended (144.3 μg kg-1). Elimination was significant over the first seven days; significant differences were detected between days 1 and 3 (p<0.001), 3 and 5 (p<0.001), and 5 and 7 (p<0.05). Chloramphenicol levels dropped below MRPL to 0.17 μg kg-1 on day 9 after the end of treatment. From day 11 to 43, chloramphenicol residues were detectable in a range from 0.091 μg kg-1 (highest) to 0.011 μg kg-1 (lowest). Our results indicate that trout muscle tissue could be compliant with health requirements for consumption 10 days after withdrawal from chloramphenicol treatment.