Purpose: A matrix validation was conducted for the Atlas® Salmonella SEN Detection Assay across various analytical parameters and food categories.
Methods: Eight matrices, each representing a category of finished product, were selected for matrix validation with the SEN assay. Each study consisted of 30, 375g Salmonella inoculated portions, of which 20 targeted fractional levels (0.2-2 CFU/portion) and 10 were inoculated to approach POD = 1 (2-10 CFU/portion). Inoculation serovars were stressed according to product type. After a stabilization period, sample replicates were enriched with BPW for 24-28 hours at 42°C. SEN assay results, which consisted of two analytical volumes at both 24 and 28 hours, where compared to results confirmed by the appropriate paired USDA MLG or FDA BAM reference culture method.
Results: For each matrix (low moisture cheese, hot dogs, tomato, liquid whole egg, peanut butter cream pie, buttermilk biscuit, caramel popcorn, and sunflower seeds) fractional positive results were obtained in the low inoculated replicates. For high level replicates, all were presumptive positive, except tomatoes, where 8 of 10 were presumptive. All presumptive results, at 24 and 28 hours for both 40 and 400 uL analytical volumes, aligned with culture results; the exception being 1 false positive in tomato and popcorn for a single assay across replicate iterations. There were no significant differences, by paired POD analysis, for the SEN assay as compared to the cultural results.
Significance: These data support the application of the SEN assay for the accurate analyses of matrices within the specified food categories and types evaluated.