食品中单增李斯特菌国标定量方法实验室验证结果与分析

Results and analysis on laboratory validation of Listeria monocytogenes by GB quantitative methods in foods

目的对食品中单增李斯特菌国标定量方法进行实验室验证。方法将单增李斯特菌标准菌株活化,经一系列稀释后染菌样品。再用单增李斯特菌国标定量方法讨论稿中平板计数和MPN法检测样品中单增李斯特菌浓度。使用3种分离培养基鉴定,对比检测效果,确定检出限。结果平板计数法的检出限为100 CFU/250 ml和10 CFU/250 ml。MPN计数法的检出限为10 CFU/250 ml和1 CFU/250 ml。平板计数法中科玛嘉单增李斯特菌显色培养基检出限低于PALCAM分离培养基,而MPN计数法中,3种分离培养基鉴定结果一致。结论平板计数法和MPN计数法均适合于食品中单增李斯特菌定量检测,MPN计数法灵敏度更高。平板计数法中科玛嘉单增李斯特菌显色培养基普遍优于PALCAM分离培养基,3种培养基都适合MPN计数法,鉴定符合率高。科玛嘉和ALOA上生长典型菌落较PALCAM容易判别。

Objective To validate GB quantitative methods of Listeria monocytogenes in foods to suit laboratory. Methods The standard strains of Listeria rnonocytogenes were activated, diluted in a series and added in samples, the GB quantita- tive methods working papers of Listeria monocytogenes was used, including plate counting and MPN method to detect the concentration of Listeria monocytogenes in the sample. Three kinds of isolation medium were used for identification, comparing to the test results and determining the detection limit. Results The detection limits of plate counting method were 100 CFU/250 ml and 10 CFU/250 ml, MPN counting method were 10 CFU/250 ml and 1 CFU/250 ml. In plate counting method, the detection limit of CHROMagar Listeria monocytogenes was less than PALCAM isolation medium, while in MPN counting method, the results of three kinds of isolation medium was identical. Conclusion Plate counting and MPN counting method are suitable for quantitative detection of Listeria monocytogenes in food, MPN count is greater sensi- tivity. CHROMagar Listeria monocytogenes chromogenic medium is generally superior with PALCAM isolation medium in plate count method, three kinds of media are suitable for MPN counting, the identification rate is high. The grown typical colonies on CHROMagar and ALOA are easier to discrimination than PALCAM discrimination.