Comparative genomic analysis of Streptococcus dysgalactiae subspecies dysgalactiae, an occasional cause of zoonotic infection

Streptococcus dysgalactiae comprise two subspecies. Typically, S. dysgalactiae subspecies equisimilis (SDSE) are large colony beta-haemolytic Group C and Group G streptococci that cause pharyngitis, skin and soft tissue infections in humans. On the other hand, S. dysgalactiae subspecies dysgalactiae (SDSD) are classically described as a-haemolytic Group C streptococci that are animal pathogens. We compared the genome sequences of five S. dysgalactiae isolated from four cases of bacteraemia in women with breast cancer, and one from fish meat. One human isolate was SDSE, all other isolates were SDSD. Zoonotic SDSD infection may be under-recognised because of lack of patient and clinician awareness, and failure to distinguish SDSD from SDSE in the routine lab. The possibility of zoonotic SDSD should be suspected in patients with bacteraemia and ascending cellulitis of the upper limb with a history of handling raw fish and meat.