Table 1.
Origin of the ST121 strains sequenced in this study.
For more details see S1 Table.
Fig 1.
Distribution of selected genetic elements among L. monocytogenes ST121 genomes.
The columns show the presence (colored)/absence (white) and full-length (green) or truncation (red) of ST121 genetic features including factors possibly involved in adaptation to survival in food production environments (A), selected prophages (B) and virulence factors (C). Yellow indicates incomplete sequence for the respective feature.
Fig 2.
Similarities between the 70 L. monocytogenes ST121 genomes revealed by tetranucleotide signature correlations.
The correlation indexes of tetra nucleotide signatures (tetra) based on whole genome sequences was calculated using JSpeciesWS [28]. Visualization was performed creating a multidimensional scaling constructed from distance matrices (MDS) using Orange 3.3 [29]. The shorter the distance between the points, the higher the similarity based on whole genome sequences. Green: strains harboring ≤ 1 prophage, red label: human isolates, italic-bold underlined label: strains devoid of plasmids. The differences between each of the genomes represent relative values.
Fig 3.
Similarities of selected L. monocytogenes ST121 prophages.
Heatmap showing the presence/absence and conservation (% identity on DNA level) between prophages of the same subtype of selected ST121 prophages. Only prophages with more than 99% similarity to each other within their respective subtypes are shown.
Table 2.
Presence/absence and similarity of selected virulence factors in ST121 and other L. monocytogenes strains.
Fig 4.
Invasion efficiency of L. monocytogenes ST121 strains in human cell lines.
Invasion efficiency of three human ST121 isolates (L58-55, N12-0367, N13-0119; all harboring a truncated inlA), the food isolate 4423 (truncated inlA), strain P02-001 (food isolate, full length inlA) and the reference strains EGDe and ScottA in Caco2 (A) and HepG2 cell lines (B). Mean values and standard deviations of the three independent biological replicates are presented. Different letters indicate significant differences (P<0.05) between the invasion efficiency of the strains.