Phylogenetic analysis and accessory genome diversity reveal insight into the evolutionary history of Streptococcus dysgalactiae

The taxonomic status of Streptococcus dysgalactiae (SD) remains controversial. Currently, SD includes two subspecies: Streptococcus dysgalactiae subsp. dysgalactiae (SDSD) and Streptococcus dysgalactiae subsp equisimilis (SDSE). While SDSE is considered an important human pathogen, SDSD has been considered a strictly animal pathogen. although occasional human infections by this subspecies have been reported in the last years. The exact incidence of SDSD human infections is globally underestimated, mainly because of the failure to distinguish SDSD from SDSE. Also, it's still largely unknown how the adaptation of SDSD differs within humans and other animals.