Streptococcus dysgalactiae Bloodstream Infections, Norway, 1999–2021

S treptococcus dysgalactiae is a potent pathogen that has similar disease manifestations as S. pyogenes, including cellulitis, necrotizing soft tissue infections, and streptococcal toxic shock syndrome (1-3).Nevertheless, in contrast to the well-established surveillance networks for S. pyogenes and S. agalactiae infections in many countries, epidemiologic reports on S. dysgalactiae are scarce (4-6).The S. dysgalactiae epithet and delineation of its 2 subspecies, dysgalactiae and equisimilis, was proposed as late as 1996, and until recently identification of this pathogen has relied predominantly on phenotypic β-hemolysis and a Lancefield agglutination reaction (7).However, the promiscuous repertoire of Lancefield antigens potentially displayed by S. dysgalactiae (mostly C or G, occasionally A or L) has caused considerable taxonomic confusion (8).In addition, S. equi harbors the C antigen and S. canis harbors the G antigen, which adds further ambiguity to speciation.Although S. equi and S. canis rarely cause human disease, their added ambiguity further illustrates that the Lancefield classification lacks taxonomic resolution to the species level for the group C and G Streptococcus (GCGS).Clinical and epidemiologic features of S. dysgalactiae have often been fragmented and concealed in separate scientific reports on group C and group G Streptococcus, a practice that continues to some extent (9-12).This practice has likely underestimated S. dysgalactiae incidence rates and clouded its clinical significance.Moreover, most recent publications involving precise identification of S. dysgalactiae comprise insufficient sample sizes or observation periods to evaluate temporal trends (3,13-15).Drawing power from the enhanced taxonomic precision of sequencing technology and mass spectrometry, we revisited S. dysgalactiae bloodstream infection epidemiology in a health region in western Norway during the past 23 years.Moreover, to explore S. dysgalactiae disease burden in a broader context, we compared S. dysgalactiae incidence against all other pathogens that cause bloodstream infections. Methods Study Setting and DefinitionsHealth Region Bergen (Bergen, Norway) had a catchment area of ≈460,000 inhabitants in 2021 and encompasses the tertiary care institution Haukeland Streptococcus dysgalactiae