The screening and identification of six commonly used antibiotics in swine kidney by a microbiological inhibition method

Abstract

A microbiological inhibition method wherein six petri dishes are used was developed for the screening and identification of macrolides, sulfonamides, aminoglycosides, tetracyclines, β-lactams, and quinolones in swine kidney. This test system is based on the growth inhibition of Bacillus subtilis BS1 on pH 7.4 and pH 9.0 agar media, Bacillus subtilis ATCC 6633 on pH 7.4 medium, Bacillus cereus on pH 6.1 medium, Micrococcus luteus on pH 6.7 medium, and Escherichia coli on pH 7.2 medium, and the use of confirmatory solutions (β-lactamase, p-aminobenzoic acid, and magnesium sulfate) for the classification and identification of antibiotics. Based on our results, we infer that the present method can effectively screen and identify most antibiotics that are used in veterinary medicine at or below the maximum residue limit levels in the kidney. Moreover, our results of specificity experiments indicated that the false-positive rates of the present method meet the standard requirements of Commission Decision 2002/657/EC. Additionally, we were able to confirm that the detection results by the present study were consistent with the confirmation results of liquid chromatography-mass spectrometry. This indicates that the microbiological inhibition method we developed is reliable for the preliminary detection of antibiotic residues in animal tissues.