Purpose: This study was conducted to validate the Atlas Salmonella SEN Detection Assay for the analysis of pet food kibble samples prepared at 1:6 and 1:10 dilution ratios with flexibility in application testing parameters.
Methods: For two studies, 375-g samples were prepared to achieve 5 high replicates (6-10 CFU/375 g), 20 low replicates (0.5-2 CFU/375 g) and 5 un-inoculated controls. Samples were bulk, dry inoculated with a lyophilized pellet of Salmonella enterica subsp. enterica serovar Typhimurium (ATCC 14028). Samples were enriched with pre-warmed 42°C BPW at a 1:6 or 1:10 dilution for studies 1 and 2, respectively, and enriched for 24 hours at 42° ± 2°C with sampling of 40 and 400 µl into Roka Transfer Tubes at 18, 20 and 24 hours. RTTs were then analyzed by the Roka Salmonella SEN Detection Assay on the Atlas instrument. Samples were cultured at 24 hours by direct streak to CHROMagar Salmonella and FDA-BAM Ch. 5. Results were tabulated and assessed by paired probability of detection.
Results: For study 1, the Atlas SEN Assay detected 12 and 5 presumptive positives in the low and high level replicates, respectively. All results correlated 100% across 18, 20 and 24 hour sampling time points and for 40 and 400 µl transfer volumes. In study 2, the assay detected 13 and 5 presumptive positives, respectively, and results, similarly, correlated 100% across all study parameters. All un-inoculated samples were negative by Atlas and culture. No significant differences were observed by paired POD. CHROMagar Salmonella performed equivalently to FDA BAM Ch. 5.
Significance: These data demonstrate flexibility of the Atlas Salmonella SEN Detection Assay and Atlas instrument for the rapid and accurate detection of Salmonella in dry kibble.