Streptococcus dysgalactiae subsp. equisimilis bacteremia in Finland: changes in emm-type distribution combined with clinical presentation

Abstract

Background: The incidence of SDSE bacteremia has risen dramatically over the past two decades, but it is unclear whether this increase is influenced by changes in the emm types of SDSE isolates. Furthermore, the relationships between emm types and clinical manifestations or disease severity are poorly understood. Methods: We conducted a retrospective, population-based study of emm types in SDSE bacteremia episodes in the Pirkanmaa health district from August 2015 to June 2018 and compared the findings to data from the same geographic area collected between 1995 and 2004. Results: During the study period, 230 episodes of SDSE bacteremia were identified. The most common emm types were stG480, stG485, and stG6, consistent with findings from the same geographic area 20 years ago. The most notable change in emm type distribution was the emergence of stG62647 as the third most common emm type, along with stG6. Despite changes in distribution, the incidence rates of isolates of all emm types identified in this study have significantly increased compared with the study conducted 1995 to 2004. Emm type StC74a was associated with higher mortality rates (OR 4.088 [95% CI 1.177–14.202]). Skin and soft-tissue infections were less common with stG485 (OR 0.455 [95% CI 0.207–1.000]), and the infection focus was more often unknown (OR 3.395 [95% CI 1.375–8.382]). StG480 was associated with arthritis (OR 5.147 [95% CI 1.227–21.589]). Conclusions: The increase in SDSE bacteremia is driven by both the rise of formerly common emm types and the newly emerged strain stG62647.