FIG. 2.

Minimum spanning tree (MST) based on MLVA data for Salmonella enterica serotype Typhimurium isolates (A) and Salmonella enterica serotype 4,5,12:i:− or Newport isolates (B) included in this study. The size of the circle is proportional to the number of isolates represented by each node, and the length of the branch is based on categorical coefficients and proportional to the number of differences between nodes. Hypothetical nodes are indicated by broken lines. Nodes encompassing multidrug-resistant isolates are shown in red, and those encompassing susceptible isolates are shown in yellow. Pansusceptible Salmonella serotype Newport isolates from farm NE299, which are characterized in the text, are indicated by their respective accession number in the tree. Interpretation of central nodes as ancestral is dependent on linear relationship between phylogenetic relationship and difference in the number of repeats, an assumption that might not be valid in all cases, particularly for isolates from Salmonella serotype Newport lineages A and B.