Performance Assessment of the Thermo Scientific SureTec Listeria monocytogenes Real-time PCR Assay – According to the ISO 16140 Standard for Listeria monocytogenes Detection in Food and Environmental Samples

Introduction: The Thermo Scientific™ SureTect™ Listeria monocytogenes Real-Time PCR Assay is a new detection method based on real-time PCR. The oligonucleotides target unique DNA sequences found only in the target microorganism and use PCR technology to amplify and detect them. If present, the target DNA is amplified and the increasing fluorescent signal is detected by the Thermo Scientific PikoReal Real-Time PCR instrument and interpreted by the Thermo Scientific SureTect™ Software.

Purpose: An independent study was conducted at ADRIA, to validate this new method in comparison to the ISO 11290-1 standard, as part of the NF Validation approval process and according to the ISO 16140 standard

Methods: The alternative method includes a single step enrichment in 24 LEB supplemented with both 24 LEB Buffer and selective supplements for 22-26h at 37°C. After DNA extraction, PCR is run performed using the PikoReal instrument.

Results: 339 food and environmental samples were analyzed for relative accuracy, sensitivity and specificity. The results demonstrate equivalent performance between the alternative and ISO 11290-1 methods. Depending on the tested (matrix/strain) pairs, the relative detection limits of the alternative method vary from 0.2 to 1.2 CFU/25 g, those of the ISO standard vary from 0.2 to 1.1 CFU/25 g. The selectivity and the specificity of the alternative method were assessed by testing 50 target strains and 30 non target strains. The alternative method was also evaluated in a ring trial involving 10 laboratories. The results of the calculated accuracy, accordance, concordance and odds ratio clearly show that the alternative method precision is equivalent to the ISO 11290-1 reference method.

Significance: The SureTect™ Listeria monocytogenes Real-Time PCR Assay is a reliable method for Listeria monocytogenes detection in food and environmental samples, and offers important economic savings by reducing time to result and handling time.