Purpose: This study was a two-part investigation. The first phase of the study examined the efficacy of using the automated Masterclave® to prepare the neutralizing Buffered Peptone Water (nBPW ) for routine laboratory use. Phase two was a comparison study between the USDA reference method for poultry rinses and the GENE-UP® Salmonella assay using the nBPW from phase one.
Methods: The nBPW was made per USDA media preparation and autoclave parameter instructions substituting the Masterclave for the generic autoclaving step. A spiking study was then performed comparing the SLM method to the USDA/FSIS MLG 4.09 for Salmonella isolation using the nBPW previously prepared. Thirty samples per method were analyzed for this comparison study. This included five uninoculated, five high (2 -5 CFU/test portion) and twenty low (0.2-2 CFU/test portion) samples. All analytical outcomes were biochemically confirmed regardless of the PCR screening result.
Results: All five uninoculated samples were confirmed negative for both methods and all five high samples confirmed positive for both methods. For the low level inoculation samples, the PCR method had six confirmed positive, whilethe reference method yielded seven positives. The dPOD and the corresponding 95% confidence interval is -0.05 (-0.32;0.23). This indicates no statistically significant difference between the two methods evaluated during this study and the efficacy of the Masterclave.
Significance: These data demonstrate that the Masterclave is a suitable method for the preparation of the new USDA nBPW formulation. These data also confirm that there are no performance issues when using this nBPW medium when testing with the GENE-UP PCR system.