Listeria monocytogenes (L. monocytogenes) is an ubiquitous bacterium that causes a severe foodborne illness. It is established that the contamination of food production facilities over long time period, are potentially one of the major food product contamination sources. L. monocytogenes persistence was observed in almost all food sectors and particularly in pork production facilities. The characterization of such L. monocytogenes contamination is therefore crucial to improve the food safety and prevent outbreaks. These strains are called persistent but this trait remains loosely defined, and no genetic determinants have been firmly associated with it. This study aims at identifying molecular markers associated with the persistence. A panel of 13 presumed persistent (PP) strains, versus 9 strains not exposed to food processing environment (NEP) strains, was constructed from the databases of the French Institute for Pig and Pork Industry (Ifip), the French National Reference Laboratory (NRL) and the European Union Reference Laboratory (EURL), the last two are hosted by Anses.

The genome sequences obtained in the present study were compared to 180 genomes of the Anses strains reference collection and 340 genomes publicly available. Two analysis were performed on the genomes, (i) an allele diversity analysis of 14 loci gathered from a review of significant functions potentially involved in the persistence capacity and (ii) a whole genome variant calling analysis to detect single nucleotide polymorphisms (SNPs) and insertions, deletions specific of persistent strains.

The preliminary results were obtained on 4 strains. The comparison of these whole genome sequencing (WGS) data with those of the whole strain panel is ongoing.