微生物显色法检测禽畜肉中混合抗生素残留

以微生物显色为原理，建立一种对畜禽肉中单一或配伍使用的抗生素进行联合初筛的高通量方法，并用色谱法对阳性样品进行验证。以大肠埃希氏菌（Escherichia coli，CICC 23657）作为指示菌，选取适当的抗生素残留提取方法，并通过单因素试验优化检测液配方及检测体系组成，最终实现对不同类别抗生素的联合检测。结果表明：选取柠檬酸-丙酮缓冲液进行提取，提取效率达到86%～88%，相对标准偏差为3.9%～4.3%；蛋白胨添加量为1.0 g/100 mL、溴甲酚紫指示剂添加量为2.0 mg/100 mL、pH值为7.2时，检测液显色效果较好；菌悬液初始吸光度（A600 nm）为0.4，检测液、菌液、样品提取液体积为150 μL∶50 μL∶100 μL时，检测效果最佳，对畜禽肉中喹诺酮类抗生素的检出限为60～180 μg/kg，氨基糖苷类检出限为60～140 μg/kg，喹诺酮类与氨基糖苷类配伍使用时的检出限为40～180 μg/kg；进一步用色谱法对50 份样品的初筛结果进行验证，无假阴性样品存在，说明该方法可用于畜禽肉中抗生素残留的初筛。

Residue Analysis of Antibiotics in Livestock and Poultry Meat by Microbial Chromogenic Assay

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.