Streptococcus dysgalactiae Bloodstream Infections, Norway, 1999-2021

Abstract

Streptococcus dysgalactiae increasingly is recognized as a pathogen of concern for human health. However, longitudinal surveillance data describing temporal trends of S. dysgalactiae are scarce. We retrospectively identified all β-hemolytic streptococcal bloodstream infections reported in Bergen, in western Norway, during 1999-2021. To explore S. dysgalactiae disease burden in a broader context, we mapped the incidence of all microbial species causing bloodstream infections during 2012-2021. We found S. dysgalactiae incidence rates substantially increased during the study period; by 2021, S. dysgalactiae was the fifth most common pathogen causing bloodstream infections in our region. We noted genotypic shifts and found that the rising trend was related in part to the introduction and expansion of the stG62647 emm-type. S. dysgalactiae is among the most common causes of bloodstream infections in western Norway, and increased surveillance and unambiguous species identification are needed to monitor the disease burden attributable to this pathogen.

Keywords: Norway; Streptococcus dysgalactiae; bacteria; beta-hemolytic streptococcus; bloodstream infections; epidemiology; incidence rates; streptococci.

Figure 1

β-hemolytic streptococcal bloodstream infections caused by Streptococcus pyogenes, S. agalactiae, and S. dysgalactiae, western Norway, 1999–2021. We calculated incidence rates for β-hemolytic streptococcal bloodstream infections in Health Region Bergen, Bergen, Norway, in 3-year periods, except 2020–2021. We calculated incidence rates as the total number of cases during each time period, divided by the number of years in the period.

Figure 2

Leading causes of bloodstream infections, western Norway, 2012–2021. We investigated bloodstream infections in Health Region Bergen, Bergen, Norway, and ranked the most common pathogens detected in each year by frequency. Red shading indicates Streptococcus dysgalactiae (abbreviated as SD). Numbers in parentheses represent the percentage of all identified cases of bloodstream infections for each pathogen. Percentages of other pathogens detected and the total number of bloodstream infections per year are shown across the bottom. B. frag, Bacteroides fragilis; C. albi, Candida albicans; E. cloa, Enterobacter cloacae; E.coli, Escherichia coli; E. faeca, Enterococcus faecalis; E. faeci, Enterococcus faecium; E. lenta, Eggerthella lenta; K. oxyt, Klebsiella oxytoca; K. pneu, Klebsiella pneumoniae; K. vari, Klebsiella variicola; P. aeru, Pseudomonas aeruginosa; P. mira, Proteus mirabilis; S. agal, Streptococcus agalactiae; S. angi, Streptococcus anginosus; S. aure, Staphylococcus aureus; S. mitis, Streptococcus mitis; S. pneu, Streptococcus pneumoniae; S. pyog, Streptococcus pyogenes; S. sali, Streptococcus salivarius.

Figure 3

Age distribution for patients with β-hemolytic streptococcal bloodstream infections, western Norway, 1999–2021. The violin plot is based on 1,176 cases of β-hemolytic streptococcal bloodstream infection in Health Region Bergen, Bergen, Norway. The total number of cases is indicated for each species. The width of each figure corresponds to the proportion of patients in that age group. White circles represent the median age and horizontal bars indicate interquartile range.

Figure 4

Age distribution for patients with streptococcal bloodstream infections, western Norway, 1999–2021. The violin plot is based on 2,033 cases of bloodstream infection caused by the 8 most common streptococcal species in Health Region Bergen, Bergen, Norway. The total number of cases is indicated for each species. The width of each figure corresponds to the proportion of patients in that age group. White circles indicate the median age and horizontal bars indicate interquartile range.

Figure 5

Distribution of the most common emm-types among Streptococcus dysgalactiae bloodstream infections, western Norway, 2005–2021. We identified most common emm-types among 351 S. dysgalactiae bloodstream infections in Health Region Bergen, Bergen, Norway. Two isolates were not available for typing, and the S. dysgalactiae subspecies dysgalactiae isolate could not be typed.

Figure 6

National surveillance data for β-hemolytic streptococcal bloodstream infections in 3 countries: A) Norway, 2004–2020; B) United Kingdom, 2012–2019; C) Finland, 2008–2017. We compiled data from annual surveillance reports published during the given time periods (,–27). The 3 countries use different surveillance methods. UK surveillance is based on voluntary reporting from the microbiology laboratories, whereas in Norway and Finland, surveillance data are collected electronically from the laboratories’ information systems. We calculated incidence rates by acquiring contemporary population data from Norway (https://www.ssb.no), the United Kingdom (https://www.ons.gov.uk), and Finland (https://www.stat.fi). We used taxonomic labels that appeared in the original publications, except GCGS, which we constructed for the purpose of this study by combining incidence data for GCS and GGS. GAS, group A Streptococcus; GBS, group B Streptococcus; GCS, group C Streptococcus; GGS, group G Streptococcus; GCGS, group C and G Streptococcus.