Population snapshot of the 400 S. aureus strains after BURP grouping. Population snapshot of the 400 S. aureus strains after grouping with the calibrated BURP ("exclude spa types that are shorter than 5 repeats" and "spa types are clustered if costs are less or equal than 4", 31 spa types were excluded). Clusters of linked isolates correspond to spa-CCs. Whereas eBURST uses the number of relatives (single locus variants, SLVs) to define founders and subfounders of groups, BURP sums up costs to define a founder-score for each spa type in a cluster. The spa type with the highest founder-score is defined founder of the cluster (blue color). Subfounders are the spa types with the second highest founder-score and are labeled in yellow. If two or more spa types exhibit the same highest founder-score, they are all colored in blue. For clarity, only the spa-CCs are labeled. Note that the spacing between linked spa types and between unlinked spa types and spa-CCs provides no information concerning the genetic distance between them.