Purpose: A study was conducted by the independent Expert Laboratory Eurofins IPL Nord to validate this new method, as part of the NF Validation approval process.
Methods: Samples, were enriched for 18-24 hours at 41.5 ± 1 °C in Buffered Peptone Water with the addition of the Salmonella supplement within 0-45 minutes after stomaching. After incubation, samples were boiled for 5 ± 1 minutes before performing the assay. All presumptive-positive samples were further confirmed after streaking on a chromogenic agar plate. This new method was compared to the ISO 6579 reference method, according to the ISO 16140 standard.
Results: A comparative study was performed on 379 products distributed over the 6 categories meat, dairy, vegetable and seafood, miscellaneous products, feeds and environmental samples of which 26% were naturally contaminated. Similar results were obtained by both methods showing a sensitivity of 96.8% for the phage method and of 96.3% for the reference method.
The 50% detection limit was found to be between 0.3 and 1.3 CFU/25 g for the alternative method and 0.3 and 1.1 for the reference method.
The collaborative study performed in 14 laboratories, showed a sensitivity of 88.4% and 92.1% for, respectively, the alternative method and the reference method. There was no statistical difference between the two methods using the Mc Nemar test at 5% level.
Significance: The SPT method was certified by AFNOR Certification to be equivalent to the reference ISO 6579 method for the detection of Salmonella in foods, feeds and environmental samples. The method is simple, fast and convenient and represents a very significant step forward in Salmonella testing, reducing the time for a result, as well as labour and media requirements