Ryan Gina, Roof Sherry, Post Laurie, Wiedmann Martin
Department of Food Science, College of Agriculture and Life Sciences, Cornell University, Ithaca, New York 14853, USA, U.S. Food and Drug Administration, College Park, MD 20740, USA.
Department of Food Science, College of Agriculture and Life Sciences, Cornell University, Ithaca, New York 14853, USA.
J Food Prot. 2015 Sep;78(9):1632-41. doi: 10.4315/0362-028X.JFP-15-098.
Assays for detection of foodborne pathogens are generally initially evaluated for performance in validation studies carried out according to guidelines provided by validation schemes (e.g., AOAC International or the International Organization for Standardization). End users often perform additional validation studies to evaluate the performance of assays in specific matrices (e.g., specific foods or raw material streams of interest) and with specific pathogen strains. However, these types of end-user validations are typically not well defined. This study was conducted to evaluate a secondary end user validation of four AOAC-validated commercial rapid detection assays (an isothermal nucleic acid amplification, an immunoassay, and two PCR-based assays) for their ability to detect Salmonella in two challenging matrices (dry pet food and dark chocolate). Inclusivity was evaluated with 68 diverse Salmonella strains at low population levels representing the limit of detection (LOD) for each assay. One assay detected all strains at the LOD, two assays detected multiple strains only at 10 times the LOD, and the fourth assay failed to detect two strains (Salmonella bongori and S. enterica subsp. houtenae) even at 1,000 times the LOD; this assay was not further evaluated. The three remaining assays were subsequently evaluated for their ability to detect five selected Salmonella strains in food samples contaminated at fractional levels. Unpaired comparisons revealed no significant difference between the results for each given assay and the results obtained with the reference assay. However, analysis of paired culture-confirmed results revealed assay false-negative rates of 4 to 26% for dry pet food and 12 to 16% for dark chocolate. Overall, our data indicate that rapid assays may have high false-negative rates when performance is evaluated under challenging conditions, including low-moisture matrices, strains that are difficult to detect, injured cells, and low inoculum levels.
用于检测食源性病原体的检测方法通常首先在按照验证方案（如美国官方分析化学家协会或国际标准化组织）提供的指南进行的验证研究中评估其性能。最终用户经常进行额外的验证研究，以评估检测方法在特定基质（如特定食品或感兴趣的原料流）中以及针对特定病原体菌株的性能。然而，这些类型的最终用户验证通常没有很好地定义。本研究旨在评估对四种经美国官方分析化学家协会验证的商业快速检测方法（一种等温核酸扩增法、一种免疫分析法和两种基于聚合酶链反应的方法）进行的二次最终用户验证，以确定它们在两种具有挑战性的基质（干宠物食品和黑巧克力）中检测沙门氏菌的能力。在低菌量水平下使用68种不同的沙门氏菌菌株评估包容性，这些菌株代表每种检测方法的检测限（LOD）。一种检测方法在检测限处检测到所有菌株，两种检测方法仅在检测限的10倍时检测到多种菌株，而第四种检测方法即使在检测限的1000倍时也未能检测到两种菌株（邦戈尔沙门氏菌和肠炎沙门氏菌亚种豪滕亚种）；该检测方法未作进一步评估。随后评估了其余三种检测方法在污染程度不同的食品样品中检测五种选定沙门氏菌菌株的能力。非配对比较显示，每种给定检测方法的结果与参考检测方法获得的结果之间没有显著差异。然而，对配对的培养确认结果进行分析发现，干宠物食品的检测方法假阴性率为4%至26%，黑巧克力的假阴性率为12%至16%。总体而言，我们的数据表明，在具有挑战性的条件下评估性能时，快速检测方法可能具有较高的假阴性率，这些条件包括低水分基质、难以检测的菌株、受损细胞和低接种量水平。
