Effective screening of antibiotic and coccidiostat residues in food of animal origin by reliable broad-spectrum residue screening tests

Abstract

Foods of animal origin are controlled for antibiotic and coccidiostat residues. The rapid residue detection is possible using reliable broad-spectrum screening tests. This study’s objective using four microbial inhibition tests for the detection and identification of antibiotic and coccidiostat residues in different foods of animal origin: Premi®Test, EXP Ampulle test, Milchtest and Screening Test for Antibiotic Residues (STAR). Four hundred and thirty (430) food samples (165 animal tissues, 152 raw cow’s milk and 113 eggs) were randomly collected and screened. Using the Premi®Test, 18 samples were positive and 6 samples dubious. Using the EXP Ampulle test, 31 samples were positive and 2 samples dubious. Using the Milchtest, 15 samples were positive and 12 samples dubious. Using the STAR, 65 samples were positive with 62 samples positive on plates specific for beta-lactams and sulphonamides, 4 samples on plates specific for aminoglycosides, 8 samples on plates specific for macrolides and beta-lactams; and 7 samples on the plates specific for tetracyclines. Retesting using penicillinase and para-aminobenzoic acid (PABA) to confirm the presence of beta-lactams or sulphonamides all potentially positive tube test samples revealed 21 samples positive for beta-lactams and 27 samples positive for sulphonamides. Further testing of sulphonamide positive chicken samples revealed the positivity for coccidiostat salinomycin which was confirmed by testing with PABA, which counteracting salinomycin inhibition. Three hundred and sixty six (366) animal food samples were negative for antibiotic and coccidiostat residues. Microbial inhibition tests are preferred for initial antibiotic screening and have also proven useful for coccidiostat screening and post-screening. HIGHLIGHTS Foodstuffs of animal origin are subject to controls on antibiotic and coccidiostat residues. Microbial inhibition tests are still the preferred choice for the initial screening of antibiotic residues in food matrices and could become a useful tool for the screening of coccidiostat residues also. More specific post-screening analysis with PABA proved unexpectedly to be a reliable tool in the preliminary detection of coccidiostat residues in poultry meat and eggs.