FIG 1.

Core SNP phylogeny of 197 S. Dublin isolates from 58 cattle herds sampled in Denmark in the period from 1996 to 2016. The tips represent herd identification numbers, and isolates from the same herd are colored the same. The map of Denmark (right) is taken from https://upload.wikimedia.org/wikipedia/commons/7/7c/Map_DK_Regions2.png. Colors in the outer ring of the phylogenetic tree correspond to the coloring of north, middle, and south Jutland in this map and indicate the regions where the strains originated. The second outer ring represents the year of S. Dublin isolation as shown on the right side of the figure. All isolates originating from persistently infected herds are labeled with a black square, and those originating from nonpersistent herds are labeled with an empty square in the third ring from the outside. The stars at the tips of the branches indicate S. Dublin isolates containing plasmids, with the filled and empty stars showing the presence or absence of a particular plasmid in the isolate, respectively.