ABSTRACT
A preliminary screening assay based on a microbial chromogenic reaction was developed to detect common antibiotic residues in meat rapidly. The assay comprised two bioassays: one for Escherichia coli and another for Geobacillus stearothermophilus. The assay was optimized and evaluated for the simultaneous screening of 30 antibiotics from five common antibiotic classes (tetracyclines, aminoglycosides, macrolides, ß-lactams, and quinolones) found in meat. Extraction using phosphate-acetonitrile buffer (pH 7.2) and a delipidating treatment using n-hexane resulted in a high extraction efficacy for the five antibiotics, without affecting the microbial color reaction. A carrier, polyvinyl alcohol (0.1 g/mL); a cross-linking agent, boric acid-sodium tetraborate solution (pH 5.5); and a bacterial suspension with an initial optical density of 1.0 were the optimal embedding conditions for stability, microbial activity, and chromogenic efficiency. The assay exhibited a 6-month shelf life, with detection limits of 40-60, 60-140, 60-100, 20-40, and 40-180 µg/kg for tetracyclines, aminoglycosides, macrolides, ß-lactams, and quinolones, respectively, which met the European Commission (37/2010) requirements for antibiotic residue limits. Our assay results were confirmed using LC-MS/MS with 160 samples, revealing a good correlation. This study demonstrates a reliable, easy-to-use, and economical method for preliminary screening of antibiotic residues in meat. This method may find an immediate application in food safety and general testing laboratories.
