Identification of <i>Salmonella</i> Infantis persistence in poultry products in the Netherlands with a role for the pESI plasmid

As Salmonella is known to be able to persist in processing environments, we investigated whether the detection of Salmonella clusters from retail poultry can be linked to a persistent source. A total of 69 Salmonella Infantis isolates from retail poultry products from four different producers between 2008 and 2020 were sequenced and their sensitivity to antibiotics was determined. The six phylogenetic clusters spanning multiple months identified by sequence analysis indicate persistence of Salmonella. In addition, the pESI megaplasmid, which is known to harbor a diversity of resistance and persistence factors, was identified in 53 of the 69 isolates. The pESI plasmid was shown to be more prevalent among more recent strains and was shown to be present in isolates from five out of six clusters. The identification of clusters by whole genome sequencing analyses helps to identify persistent strains, as was shown in this study for S. Infantis. Moreover, the detection of pESI in these S. Infantis isolates suggests that pESI has a role in persistence and thus in the further spread and increased prevalence of S. Infantis.