Evaluation of the Thermo Scientific SureTect(TM) Listeria Species PCR Assay in a Broad Range of Foods and Selected Environmental Surfaces: Pre-Collaborative and Collaborative Study, First Action 2021.06

BACKGROUND: The Thermo Scientific SureTect™ Listeria species PCR assay utilizes Solaris(TM) reagents for performing PCR for the rapid and specific detection of Listeria species in a broad range of foods and selected environmental surfaces. OBJECTIVE: To demonstrate reproducibility of the Thermo Scientific SureTect Listeria species PCR assay in a collaborative study using a challenging matrix, full-fat cottage cheese (25 g), to extend the scope of the method. METHODS: In the collaborative study, the candidate method was compared to the US Food and Drug Administration/Bacteriological Analytical Manual (FDA/BAM) Ch. 10 Listeria reference method. The candidate method used two PCR thermocyclers, the Applied Biosystems QuantStudio™ 5 Real-Time PCR instrument (QS5) and the Applied Biosystems 7500 Fast Real-Time PCR instrument (7500 Fast). The candidate method included its own confirmation procedure. Eighteen participants from 10 laboratories located within the United States and Europe were solicited for the collaborative study, with 12 participants submitting valid data. Statistical analysis was conducted according to the probability of detection (POD) statistical model. In addition, in order to extend the scope of the method, seven matrix studies were performed comparing the candidate method to the FDA/BAM reference method. One of these matrixes was also compared to the ISO 11290–1:2017 Microbiology of the food chain—Horizontal method for the detection and enumeration of Listeria monocytogenes and of Listeria spp.—Part 1: Detection method reference method. RESULTS: In the collaborative study, the difference in laboratory results indicates equivalence between the candidate method and reference method for the matrix evaluated and the method demonstrated acceptable inter-laboratory reproducibility as determined in the collaborative evaluation. The two PCR instruments used in the study performed equivalently. All presumptive positives were confirmed via the alternative confirmation procedure. In the pre-collaborative studies, the results showed comparable performances between the candidate method and the reference method for all matrixes tested. CONCLUSION: Based on the data generated, the method demonstrated acceptable inter-laboratory reproducibility data and statistical analysis. HIGHLIGHTS: Due to the COVID-19 pandemic, some participants had to be trained remotely. Additionally, 25 g full-fat cottage cheese is known to be a challenging matrix to test. No unusual cross-contamination, or false-positive/negative data was reported, highlighting the ease of use, reproducibility, and robustness of the candidate method.