Abstract：A new microbial chromogenic assay was developed to analyze antibiotic residues in animal-derived food and after that, the positive samples were identified by a high-performance liquid chromatography-tandem mass spectrometric (HPLC-MS) method. E.coli was used as the indicator strain to produce a 96-well microplate for detecting 15 kinds of quinolones. Muscle samples were extracted by pH 7.4 phosphate-acetonitrile buffer. This system of microbial chromogenic assay consisted of 150 μL the reaction solution, 50 μL of bacterial suspension (the initial A600 nm value was around 0.4), and 100 μL of the extract solution. The assay proved to be simple and cheap and the results were accurate and easy to interpret. The detection limits for 15 kinds of quinolones drugs were 40‒200 μg/kg, meeting the domestic and international requirements for the determination of antibiotic residue limits. Consistent results were obtained for 50 samples of animalderived food by microbial chromogenic assay and HPLC-MS, indicating that the assay could be used to detect antibiotic residues in animal-derived food with good stability.
