DETECTION OF 4-QUINOLONE RESIDUES IN RAINBOW-TROUT (ONCORHYNCHUS-MYKISS WALBAUM) MUSCLE USING A BIOASSAY

The development of a bio-assay for the detection of 4-quinolone residues in rainbow trout (Oncorhynchus mykiss Walbaum) muscle is described. The bio-assay depends upon a particularly sensitive isolate of Yersinia ruckeri (Fish Diseases Laboratory, 39/81, Weymouth; National Collections of Industrial and Marine Bacteria, 13282, Aberdeen) allowing detection of residues down to 0.02 mug/ml in muscle extracts. Traditional problems associated with bio-assays such as accuracy and precision were examined and potential cross-reaction with other antibiotics licensed for use in aquaculture which could affect the assay was also investigated. Alongside existing physicochemical techniques the bio-assay potentially provides an additional method both for quantifying residue levels in pharmacokinetic studies and for carcass screening prior to human consumption.