Evaluation of VIDAS® UP Salmonella (SPT) Assay for the Detection of Salmonella in a Variety of Foods and Environmental Samples: Collaborative Study

Abstract

The VIDAS UP Salmonella (SPT) uses recombinant phage proteins to detect Salmonella species in human and animal food products and production environmental samples after 18-26 h of enrichment. The VIDAS SPT assay is performed with the automated VIDAS or mini-VIDAS instruments. The VIDAS SPT method was compared in a multilaboratory collaborative study to the U.S. Department of Agriculture/Food Safety and Inspection Service-Microbiology Laboratory Guidebook (USDA/FSIS-MLG) 4.05 (2011) Isolation and Identification of Salmonella from Meat, Poultry, Pasteurized Egg and Catfish Products reference method following the current AOAC guidelines. A total of 15 laboratories representing government, academia, and industry throughout the United States participated. One matrix, raw ground beef, was analyzed using two different test portion sizes, 25 and 375 g. Each test portion was artificially contaminated with Salmonella at three inoculation levels, an uninoculated control level (0 CFU/test portion), a low inoculum level (0.2-2 CFUltest portion), and a high inoculum level (2-5 CFU/test portion). In this study, 1656 unpaired replicate samples were analyzed. Of those unpaired replicates, 476 were presumptive positive by the VIDAS method, with 475 confirmed positive by the traditional confirmation procedures and 476 confirmed positive by an alternative confirmation procedure. There were 411 confirmed positive replicates by the USDA/FSIS-MLG reference method. Statistical analysis was conducted according to the probability of detection (POD). For the low-level 375 g test portions, the following dLPOD values, with 95% confidence intervals, were obtained: 0.01 (-0.12, +0.15) for samples confirmed following the traditional confirmation; 0.02 (-0.18, +0.2) for samples confirmed following traditional confirmation on IBISA and ASAP; and 0.03 (-0.18, +0.24) for samples confirmed following the alternative confirmation on IBISA and ASAP. For the low-level 25 g test portions, the following dLPOD values, with 95% confidence intervals, were obtained: 0.41, (0.32, +0.49) for samples confirmed following the traditional confirmation, the traditional confirmation on IBISA and ASAP, and the alternative confirmation on IBISA and ASAP. With 0.0 within the confidence intervals for the 375 g test portions, there was no statistically significant difference in the number of positive samples detected by the VIDAS SPT method and the USDA/FSIS-MLG method at the 0.05 level. For the 25 g test portions, a statistically significant difference was observed between the VIDAS SPT method and the reference method for the low inoculum level, where the VIDAS SPT method recovered a higher number of positive results than the reference method. It is recommended that the VIDAS SPT method with the optional ASAP and IBISA agar confirmation method be adopted for Official First Action status for the detection of Salmonella in a variety of foods and environmental samples.