Purpose: To demonstrate the equivalence of GDS and new mEHEC enrichment to reference culture methods for the detection of Salmonella in selected foods and environmental surfaces.
Methods: Eight food matrices (cooked poultry, raw beef trim, raw ground beef, leaf lettuce, spinach, mixed greens, strawberries, and almonds ) and 2 environmental surfaces (stainless steel and rubber) were included in the study. For each sample type, 20 samples were inoculated with low levels of Salmonella, 5 samples were inoculated with high levels of Salmonella and 5 uninoculated samples were included as controls. 25 g and environmental samples were enriched at a 1:10 sample to media ratio in mEHEC for 8 – 18h at 42°C. 375 g samples were enriched at a 1:5 sample to media ratio in mEHEC for 10 – 18h at 42°C. All samples were analyzed using GDS for Salmonella Tq and the reference culture methods, EN ISO 6579:2002. Inclusivity and exclusivity of GDS was determined by analyzing 105 strains of Salmonella and 30 strains of potential cross-reacting organisms.
Results: Fractional recovery of Salmonella was achieved for all food types tested. In total, there were valid results from 300 samples and controls. POD statistical analyses of the unmatched samples indicated that for all foods analyzed, there was no statistical difference between the GDS presumptive compared to the GDS confirmed. Furthermore, GDS method results were statistically not different than the reference culture method for the detection of Salmonella.
Significance: The newly harmonized mEHEC enrichment for both Salmonella and E. coli O157:H7 saves time and lowers lab testing costs for customers.