While sequence-based typing (SBT) has been used for outbreak investigations because of its historically lower cost, whole genome sequencing (WGS) of eight Lp1 and Lp12 strains, in addition to a large number of Lp1 strains linked to geographic outbreaks1112131415161718, has revealed how genetic exchange plays a role in shaping the virulence potential of the species. Genes encoding features such as drug resistance islands, secretion systems and a large repertoire of secreted effector proteins19 are part of the mobile accessory portion of the pan-genome.