Evaluation of Roka Atlas Salmonella method for the detection of Salmonella in egg products in comparison with culture method, real-time PCR and isothermal amplification assays

With the increasing focus on the food safety, rapid methods for the detection of Salmonella are crucial for both food industry and regulatory agencies. Recently, many molecular methodologies with diverse technologies have been introduced. Roka Atlas (R) Salmonella Assay (SEN) is a molecular method that uses ribosomal RNA as target for detection, which is theoretically more sensitive than PCR or isothermal amplification methods that target the DNA sequences of single genes. In this study, SEN assay was compared with four PCR- and isothermal amplification -based assays and a culture method, such as the MicroSEQ (R) Salmonella spp. Detection kit (MicroSEQ), 3M (TM) Molecular Detection Assay (MDA) Salmonella, ANSR (TM) Salmonella Assay (ANSR), and Pro-ArnpRT (TM) SALM spp. Kit (Pro-AmpRT). Food samples were prepared and analyzed according to the current U. S. Food and Drug Administration (FDA) Bacteriological Analytical Manual (BAM) Salmonella culture method. A total of 155 bacterial isolates (121 for Salmonella inclusivity and 34 for Salrneonlla exclusivity) and 200 egg product samples inoculated at a level of 1-5 CFU/25 g were analyzed. The study also estimated the limit of detection of these molecular methods, and illustrated their advantages and disadvantages. For exclusivity, all 34 non-Salmonella isolates were negative by all 5 molecular methods studied. For inclusivity, all 121 Salmonella isolates were positive by MDA, ANSR, and Pro-AmpRT methods. However, the SEN and MicroSEQ results were negative for 9 samples inoculated with Salmonella bongori. The detection limit of the 5 molecular methods ranged from 1.76 to 3.76 log CFU/mL pre-enrichment culture, with the SEN assay being the most sensitive (1.76 - 2.64 log CFU/mL). The results indicated that the SEN assay was as effective and sensitive in detecting Salmonella enterica in egg products as was the FDA BAM culture method and the 4 other isothermal amplification and PCR methods evaluated in the study.