Purpose: The InSITE Salmonella device is designed to swab a large area for possible Salmonellae contamination, pre-enrich and then selectively enrich in the same device giving a presumptive positive in 24 h from sample collection. This allows better and more rapid surveillance of high risk surfaces.
Methods: Salmonella Typhimurium ATCC 14028 and Salmonella arizonae ATCC 13314 were grown and diluted into diluent. Sterile stainless steel squares were inoculated with 100 µl from each dilution -1 through to -9 and air dried overnight under asepsis. Each square was swabbed with one InSITE Salmonella device and incubated at 6 h in the pre-enrichment phase, a further 18 h in the selective phase. Devices are positive if a vivid yellow color appears in the viewing window. All devices used in the study were analyzed for confirmation of positivity using the BAM Salmonella confirmation steps with a final identification by biochemistry. Directly inoculated devices without a drying step were performed as controls.
Results: The drying of the Salmonella on the stainless steel surface rendered the bacteria stressed. Dilutions -1, -2, -3 and -4 were all positive for both Salmonella Typhimurium and for Salmonella arizonae. The -5 dilution dried was also detected using the InSITE Salmonella device. All dilutions from the directly inoculated devices were positive. All devices were then confirmed for negativity and positivity using a confirmation protocol from BAM, the confirmation was 100% for both positives for Salmonella but also negative for Salmonella from those swabs that indicated a presumptive negative at 18 h.
Significance: An easy to use enclosed device that will reliably indicate presumptive positive and negative Salmonella from surfaces has advantages to many food producers and manufacturers.