Purpose: The purpose of the study was to verify the performance of the SureTect Listeria assays on the Applied Biosystems 7500 Fast PCR platform with pasteurized whole milk, cold smoked salmon, roast beef, and stainless steel.
Methods: Hybrid Listeria monocytogenes and Listeria species assays were compared to a slightly amended version of the ISO 11290-1:1996 including Amendment 1:2004 reference method. The reference method’s primary enrichment was conducted in 24LEB followed by secondary enrichment in Fraser Broth. Food matrices were spiked with L. monocytogenes or L. innocua isolates. Isolates for roast beef and whole milk were heat stressed prior to spiking. Ten replicate bags were set up for each matrix. All matrices were held at +4°C for 4 days prior to the enrichment. The spiking level was between 0.5 - 0.83 CFU/25 g food. The stainless steel was spiked with 24 CFU/plate to account for the Listeria die off on the surface. Samples were tested after a 22-hour enrichment step. PCR results were confirmed by plating on Thermo Scientific™ Brilliance™ Listeria chromogenic plates followed by identification of Listeria species using Thermo Scientific™ Microbact™ Listeria 12L kit.
Results: The hybrid Listeria methods were comparable to the amended reference method for the four matrices following an enrichment time of 22 h.
Significance: The study provided the evidence that the high throughput SureTect methods offer rapid, easy to use and reliable workflow for the detection of Listeria in food and environmental samples.