Interlaboratory validation trial report on multiplex real-time PCR method for molecular serotyping and identification of the 30 major clonal complexes of Listeria monocytogenes circulating in food in Europe

The performance of a new method developed in 2021 by the European Union Reference Laboratory (EURL) for Listeria monocytogenes based on 12 multiplex real-time PCR, allowing the identification of the molecular serotype and the 30 major L. monocytogenes multilocus sequence typing clonal complexes (CC), was assessed through a European interlaboratory validation trial (ILVT). This ILVT was adapted from ISO standard 16140 part 6. Overall, 98 blinded pure strains of Listeria (monocytogenes or spp.), previously characterized by the EURL, were sent to 15 laboratories distributed in 11 countries. The molecular serotype had to be identified for 20 strains of the ILVT panel, while CC identification had to be performed for the whole panel. The results of the 12 multiplex real-time PCR were reproducible between the participating laboratories with high individual concordance values for molecular serotyping (100%) and CC identification (90.8%–100%) irrespective of DNA extraction protocols, PCR master mixes,and thermocycler diversity. Master mixes identified as incompatible with some of the multiplex real-time PCR were excluded from the method. The overall concordance of the results was sufficient for the method to be confidently applied in other laboratories involved in L. monocytogenes typing.

Article en accès ouvert sur le site de l'éditeur ici.