乳粉中沙门氏菌能力验证样品研制及应用评价

Preparation and application evaluation of Salmonella proficiency test samples in milk powder

目的研制均一性和稳定性符合能力验证要求的沙门氏菌能力验证样品,并应用于乳粉中沙门氏菌检测的能力验证。方法选取本实验室保存的ATCC、CMCC标准菌株及食品中分离菌株作为能力验证样品的菌株来源,采用基质辅助激光解吸电离飞行时间质谱和全自动微生物分析系统进行种属确认,并对沙门氏菌标准菌株进行血清学分型;采用冷冻干燥技术制备沙门氏菌能力验证样品,取阴性、阳性各20个能力验证样品添加灭菌乳粉基质后按照国标方法进行均匀性检验,并参照CNAS—GL003:2018《能力验证样品均匀性和稳定性评价指南》,采用最大可能数法(most probable number,MPN)对能力验证样品进行沙门氏菌计数,评价其储藏稳定性和运输稳定性;根据随机数字表对阴性、阳性样本进行编码,以防止实验室间数据串通。结果乳粉中沙门氏菌检测能力验证阳性样品于-20℃保藏12个月、4℃保藏7 d后,沙门氏菌含量仍能达到10^(3)MPN/g以上;于25和37℃保藏7 d后均能检出沙门氏菌,稳定性较好。17家实验室应用本样品进行了能力验证,报送结果与预期一致,结果评价均为满意。结论研制的沙门氏菌能力验证样品能够满足乳粉中沙门氏菌检测能力验证的需求,本次能力验证可以真实的反应参试实验室的检验能力。

Objective To develop proficiency test samples of Salmonella with uniformity and stability meeting the requirements of proficiency test,and apply the samples to the proficiency test of Salmonella in milk powder.Methods The standard strains of ATCC,CMCC and isolated strains from food in our laboratory were selected as the source of proficiency testing samples.The species identification was carried out by matrix assisted laser desorption ionization time of flight mass spectrometry and automatic microbial analysis system,and the serological typing of Salmonella standard strains was carried out;The freeze-drying technology was used to prepare Salmonella proficiency test samples.After 20 negative and 20 positive proficiency test samples were added with sterilized milk powder matrix,the homogeneity test was carried out according to the national standard method.According to CNAS—GL003:2018 Guidelines for the evaluation of homogeneity and stability of proficiency test samples,the most probable number(MPN)method was used to count the Salmonella in the proficiency testing samples to evaluate their storage stability and transportation stability;The negative and positive samples were coded according to random number table to prevent data collusion between laboratories.Results The positive Salmonella test samples showed good stability,and could be stored at-20℃for 12 months and 4℃for 7 d,the Salmonella content could reach more than 10^(3)MPN/g;Meanwhile,after the samples were stored at 25 and 37℃for 7 d,Salmonella could still be tested.Seventeen laboratories had attended proficiency testing using this sample,and the submitted results were consistent with expectations,and the proficiency test evaluation results were all satisfactory.Conclusion The Salmonella proficiency test samples can meet the requirements for the proficiency test of Salmonella in in milk powder.This proficiency test can reflect the real capabilities of the participating laboratories.