Occurrence, Persistence, and Virulence Potential ofListeria ivanoviiin Foods and Food Processing Environments in the Republic of Ireland

Abstract

The aim of this study was to assess the occurrence ofL. ivanoviiin foods and food processing environments in Ireland, to track persistence, and to characterize the disease causing potential of the isolated strains. A total of 2,006 samples (432 food samples and 1,574 environmental swabs) were collected between March 2013 and March 2014 from 48 food business operators (FBOs) belonging to different production sectors (dairy, fish, meat, and fresh-cut vegetable). Six of the forty-eight FBOs had samples positive forL. ivanoviion at least one sampling occasion.L. ivanoviiwas present in fifteen samples (fourteen environmental samples and one food sample). All but one of those positive samples derived from the dairy sector, whereL. ivanoviiprevalence was 1.7%. Six distinguishable pulsotypes were obtained by PFGE analysis, with one pulsotype being persistent in the environment of a dairy food business. Sequence analysis of thesigBgene showed that fourteen isolates belonged toL. ivanoviisubsp.londoniensis, while only one isolate wasL. ivanoviisubsp.ivanovii. Cell invasion assays demonstrated that the majority ofL. ivanoviistrains were comparable toL. monocytogenesEGDe in their ability to invade CACO-2 epithelial cells whilst four isolates had significantly higher invasion efficiencies.