title: Influence of storage temperature on gene expression and virulence potential of Listeria monocytogenes strains grown in a salmon matrix.
abstract: Little is understood about the impact of environmental conditions on the virulence plasticity of Listeria monocytogenes strains grown in food. In this report, we monitored changes in the virulence properties of one high virulent (CCUG 3998) and one low virulent (442) L. monocytogenes strains grown on raw salmon (Salmo salar L.). The effect of temperature exposures (0 degrees C, 4 degrees C and 20 degrees C) on the expression levels of virulence genes (hlyA, actA, inlA and prfA), invasion into Caco-2 cells and in vivo mouse infection was analysed. Our results showed that L. monocytogenes virulence genes are differentially expressed when salmon is stored at different temperatures. Of the four virulence genes, the transcript levels for inlA were strongly affected, which correlated with the strain's virulence capacity as assessed by Caco-2 cells. In contrast to CCUG 3998, the virulence of strain 442 was altered with tested conditions. This strain maintains its low virulence status as far as salmon is stored at lower temperatures, but increases its virulence at higher temperatures. These results lead to the indication that exposure to abuse temperature conditions might influence the virulence potential of low pathogenic L. monocytogenes strains in salmon.
authors.affiliation: National Veterinary Institute, Ullevaalsveien 68, Sentrum N-0106, Oslo, Norway. samuel.duodu@vetinst.no
authors.forename: Samuel
authors.initials: S
authors.lastname: Duodu
authors.forename: Arne
authors.initials: A
authors.lastname: Holst-Jensen
authors.forename: Taran
authors.initials: T
authors.lastname: Skjerdal
authors.forename: Jean-Michel
authors.initials: JM
authors.lastname: Cappelier
authors.forename: Marie-France
authors.initials: MF
authors.lastname: Pilet
authors.forename: Semir
authors.initials: S
authors.lastname: Loncarevic
mesh_terms: D000818:Animals; D001422:Bacterial Adhesion / Q000502:physiology; D018938:Caco-2 Cells; D015169:Colony Count, Microbial; D003257:Consumer Product Safety; D005516:Food Microbiology; D005519:Food Preservation / Q000379:methods*; D015964:Gene Expression Regulation, Bacterial / Q000235:genetics; D006801:Humans; D008089:Listeria monocytogenes / Q000235:genetics / Q000472:pathogenicity*; D012474:Salmon / Q000382:microbiology*; D017747:Seafood / Q000382:microbiology*; D013696:Temperature; D014774:Virulence / Q000235:genetics*