The projected evolution of the two clades of E. faecium . A figure addressing the possible scenarios which may have occurred in the evolution of Enterococcus faecium resulting in the HA-clade and CA-clade. Specifically, a primordial type of Enterococcus faecium split into early community isolates which had homologous core genomes with significant sequence differences (e.g., the pbp5-S or pbp5-R allele). These early community groups further segmented into a hospital-associated clade and the community clade. Scenario one depicts that these lineages could recombine with each other (represented by the bent dashed arrow) resulting in hybrid strains, scenario two depicts community and hospital ARE isolates splitting from the same ancestor, scenario three depicts ARE clones evolving from the animal reservoir, and scenario four depicts animal ARE isolates representing descendants of hospital ARE transferred from humans to their pets.