Streptococcus dysgalactiae

Streptococcus dysgalactiae is a gram positive, beta-haemolytic, coccal bacterium belonging to the family Streptococcaceae. It is capable of infecting both humans and animals, but is most frequently encountered as a commensal of the alimentary tract, genital tract, or less commonly, as a part of the skin flora. The clinical manifestations in human disease range from superficial skin-infections and tonsillitis, to severe necrotising fasciitis and bacteraemia.^[1] The incidence of invasive disease has been reported to be rising.^[2][3][4] Several different animal species are susceptible to infection by S. dysgalactiae, but bovine mastitis and infectious arthritis in lambs (joint ill) have been most frequently reported.^[5][6]

Streptococcus dysgalactiae is currently divided into the subspecies Streptococcus dysgalactiae subsp. equisimilis and Streptococcus dysgalactiae subsp. dysgalactiae; the former mostly associated with human disease, and the latter almost exclusively encountered in veterinary medicine.^[7] Their exact taxonomic delineation, however, is a matter of ongoing debate (See taxonomy).

The names are derived from Greek; Streptococcus meaning chain forming (Streptos) rounded berry-like bodies (kokkos), referring to their usual appearance under a light-microscope. Dys (bad) galactiae (milk) alludes to their propensity to cause bovine mastitis. Equi (horse) similis (like) infers similarity to the closely related species, Streptococcus equi.