Streptococcus dysgalactiae is a Gram-positive bacterium. 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. Less commonly it can present as pneumonia, endocarditis, genital or intra-abdominal infections. Primary bacteraemia, infection without identifiable focal origin, comprises approximately 20% of the reported cases. The incidence of invasive disease has been reported to be rising.
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.