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UK: AOAC Validation Gain Additional Layer of Confidence When Testing for Salmonella

Editor: MA Alexander Stark

The Thermo Scientific Sure Tect Salmonella Species PCR Assay has received approval by AOAC International (AOAC-OMA claim) for a broad range of foods and select environmental surfaces, including challenging, high-risk matrices and large sample sizes.

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The Thermo Scientific Sure Tect Salmonella Species PCR Assay received approval by AOAC International.
The Thermo Scientific Sure Tect Salmonella Species PCR Assay received approval by AOAC International.
(Source: Thermo Scientific)

Basingstoke/UK — The Sure Tect Salmonella Species PCR Assay from Thermo Fisher Scientific has been granted AOAC Official Method Analysis (OMA) status. The method was validated against the FDA-BAM, USDA-FSIS and ISO reference methods, giving food laboratories the world over confidence in the robustness of the assay and the accuracy of its results.

The AOAC-OMA claim for the Sure Tect Salmonella Species Assay covers 32 matrices — currently one of the broadest range of foods and selected environmental surfaces covered for an AOAC-OMA validated Salmonella test. This includes challenging to test high-risk products from a broad range of foods and production environments, such as cocoa products and other low moisture foods, raw meats and poultry meats, fruits & vegetables, milk & dairy products and ready-to-eat foods. According to the company, this Salmonella Species PCR Assay is the first to offer a validated method for Salmonella testing in large samples for multiple matrix types such as raw beef meats, produce, cocoa and chocolate.

In the AOAC study, 32 matrices were tested using the Sure Tect Salmonella Species PCR Assay (candidate method) and the FDA/BAM, USDA/FSIS and ISO reference methods. These included eleven foods not previously tested as part of the original AOAC-Performance Tested Methods (PTM) program. These were selected after an audit of currently available methods highlighted a requirement for tools that enabled larger sample size testing and the addition of some of the more challenging and higher-risk products.

The new matrices include 25 g samples of cut cabbage, cut mango, Cheddar cheese, Feta cheese, and cream, as well as up to 375 g ground beef, beef trim, spinach, cocoa powder, cocoa butter, cocoa liquor and dark chocolate (> 70 percent cocoa).

Testing Challenging Samples

The collaborative part of the study was conducted using samples of 375 g cocoa powder. The challenging nature of detecting of Salmonella in such samples and large test portions is well documented. In addition, the phenols present in cocoa can inhibit PCR, making it a particularly challenging matrix both in terms of creating the right conditions for the organism to grow, and using PCR to detect it.

Thanks to the assay’s simple workflow and minimal handling steps, the team was able to demonstrate and train collaborator laboratories’ staff on how to use the Sure Tect Salmonella Species PCR Assay workflow remotely via online training sessions. This approach was necessary for some participants due to Covid restrictions and was well received and highly effective.

The study found no issues in terms of inhibition or false positive/negative data, confirming the robustness of the method in even when used under the most challenging of conditions.