Abstract：A new microbial chromogenic assay was developed for high throughput screening for single and compatible combinations of antibiotic residues in livestock and poultry meat, and it was validated by liquid chromatography (LC). Escherichia coli was used as the indicator strain to detect a variety of antibiotics simultaneously. The optimal extraction conditions were determined and the reaction system and conditions were optimized by one-factor-at-a-time method. The results showed that citric acid-acetone mixture was the solvent of choice for the extraction procedure, giving an extraction efficiency of 86%–88% with a relative standard deviation ranging from 3.9% to 4.3%. Addition of 1.0 g/100 mL of peptone and 2.0 mg/100 mL of bromocresol purple and pH adjustment to 7.2 were found to be the optimal conditions for chromogenic reaction. The optimal detection conditions were as follows: initial absorbance value (A600 nm) of bacterial suspension 0.4, and ratio of reaction system to bacterial suspension to sample extract 150:50:100 (V/V). The limit of detection of the proposed method was 60–180, 60–140 and 40–180 μg/kg for quinolones, aminoglycosides and their combinations in livestock and poultry meat, respectively. For 50 positive samples with antibiotic residue determined by the microbial chromogenic assay, no false negative results were obtained. Thus this assay can be used in screening for antibiotic residues in livestock and poultry meat.
2019, Vol. 33 
