Purpose: The aim was to develop and to validate a rapid screening method that significantly minimizes the complexity and length of enrichment for PCR-based detection of Listeria and Salmonella in environmental and food samples.
Methods: Actero™ Listeria Enrichment Media and Actero™ Salmonella Enrichment Media, optimized for rapid recovery of Listeria and Salmonella, were used for enriching these pathogens from environmental and food samples. Enriched samples were tested using BAX® System real-time PCR assays. For Listeria, seven internal studies and one external validation study were conducted that included 240 environmental (stainless steel, plastic and sealed concrete) and 240 food (hot dog, bagged fresh spinach, frozen cooked shrimp and soft Mexican-style cheese) samples. For Salmonella, five internal and two external validation studies were completed and included 240 environmental (stainless steel and plastic) and 240 food (dry pet food, chocolate liquor and milk chocolate) samples. The alternative detection methods were compared to the appropriate reference methods. The results were evaluated using the AOAC Probability of Detection statistical model.
Results: No false negative or false positive results were observed after enriching at 35°C for 20 - 26 hours for Listeria spp. and 14 - 22 hours for Salmonella spp. The detection of Listeria and Salmonella in environmental and food samples enriched with the proposed media using the real-time PCR assays showed equal or better performance as compared to the gold standard methods.
Significance: These alternative methods were determined to be reliable, accurate, and faster than other methods for detection of Listeria and Salmonella.