EVALUATION OF THE EUROPEAN 4-PLATE TEST AS A TOOL FOR SCREENING ANTIBIOTIC RESIDUES IN MEAT SAMPLES FROM RETAIL OUTLETS

A modified 4-plate test was used to screen 4795 meat samples from reta il outlets in the European Community (EC). This microbial inhibition t est uses 3 media seeded with Bacillus subtilis at different pH values (6, 7.2, or 8) and a fourth medium seeded with Micrococcus luteus. Pos itive samples were confirmed by a receptor test for macrolides, a thin -layer chromatographic method for sulfonamides, or an enzyme-linked im munosorbent assay test for tetracyclines. Inhibition on M. luteus plat es, often by beef and veal samples, could not be confirmed. Circumstan tial evidence indicated these test results had to be considered presum ptively false positives. Of the samples, 95 inhibited at least one pla te seeded with B. subtilis. Usually, samples were positive on more tha n one plate: 70 samples were positive on all 3 plates, and only 6 samp les did not inhibit the plate at pH 6. The majority of positive result s on plates seeded with B. subtilis, 77 of 89 samples tested, containe d tetracycline antibiotics. One sample also contained sulfadimidine. T wo other samples contained high levels of enrofloxacine and ciprofloxa cine. The 4-plate test is not sensitive enough to detect sulfonamides and quinolones at the EC maximum residue limits, but higher levels may cause inhibition. The 4-plate test can be used to detect meat samples containing tetracycline residues, but the method is too complicated w hen used only for that purpose.