Tomás Fornés David, McMahon Wendy, Moulin Julie, Klijn Adrianne
Quality and Safety Department, Nestlé Research Center, Vers-chez-les-Blanc, CH-1000 Lausanne, Switzerland.
Mérieux NutriSciences, Silliker Food Science Center, 3600 Eagle Nest Drive, South Building, Crete, IL 60417, USA.
Int J Food Microbiol. 2017 Mar 20;245:13-21. doi: 10.1016/j.ijfoodmicro.2017.01.005. Epub 2017 Jan 16.
Pathogen monitoring programs play a crucial role in the verification of the effectiveness of implemented hygiene control measures. Sampling and testing procedures included in pathogen monitoring involve the analysis of multiple test portions where all samples must be negative for the presence of pathogens for a certain test portion size. Many food safety programs require increased testing due to the risks that a pathogen may be present. Analyzing more than one test portion could prove to be expensive and labor intensive. When more than one test portion for a specified food item is to be tested, the test portions could be combined to form a pooled test portion to reduce laboratory workload, costs of reagents and further confirmatory steps, but only when evidence is available that pooling does not affect on the number of false negative results for different matrices. This study has been performed to demonstrate the equivalence of test portion pooling for Salmonella detection with five different methods using cultural, ELISA and Real Time PCR technologies. Twenty-three (23) different food items including confectionary products, meal components, infant formula, pet food and powdered beverages were validated. Other complementary parameters like impact of minimum and maximum incubation time for pre-enrichment, temperature profile, pH and Salmonella concentration after the pre-enrichment and background flora have also been considered in the study. The results showed that pooling test portions up to 375g for Salmonella detection is valid for the methods that were tested. Relative level of detection (RLOD) values for 22 of the food items tested were acceptable (i.e. lower than 2.5) when comparing the reference sample size (25g) against the alternative pooled sample size (375g), provided the enrichment broth was pre-warmed and maximum incubation time is respected.
病原体监测程序在验证所实施的卫生控制措施的有效性方面发挥着关键作用。病原体监测中包含的采样和检测程序涉及对多个检测部分进行分析，对于特定的检测部分大小，所有样本的病原体检测结果必须为阴性。由于存在病原体的风险，许多食品安全计划要求增加检测。分析多个检测部分可能会被证明成本高昂且 labor intensive。当要对指定食品的多个检测部分进行检测时，可以将这些检测部分合并形成一个混合检测部分，以减少实验室工作量、试剂成本和进一步的确认步骤，但前提是有证据表明合并不会影响不同基质的假阴性结果数量。本研究旨在使用培养、ELISA 和实时 PCR 技术，通过五种不同方法证明用于沙门氏菌检测的检测部分合并的等效性。对包括糖果产品、膳食成分、婴儿配方奶粉、宠物食品和粉末饮料在内的 23 种不同食品进行了验证。研究中还考虑了其他补充参数，如预富集的最短和最长培养时间的影响、温度曲线、pH 值以及预富集后的沙门氏菌浓度和背景菌群。结果表明，对于所测试的方法，合并高达 375 克的检测部分用于沙门氏菌检测是有效的。当将参考样本大小（25 克）与替代的混合样本大小（375 克）进行比较时，在预温育富集肉汤并遵守最长培养时间的情况下，所测试的 22 种食品的相对检测水平（RLOD）值是可接受的（即低于 2.5）。
