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Necrotizing soft tissue infections caused by Streptococcus pyogenes and Streptococcus dysgalactiae subsp. equisimilis

T Bruun1, B R Kittang, B J de Hoog

  • 1Department of Clinical Science, University of Bergen, Bergen, Norway; Department of Medicine, Haukeland University Hospital, Bergen, Norway.

Clinical Microbiology and Infection : the Official Publication of the European Society of Clinical Microbiology and Infectious Diseases
|June 26, 2013
PubMed

Insights

Streptococcus pyogenes (group A streptococcus, GAS) causes necrotizing soft tissue infections (NSTI). Other beta-hemolytic streptococci, like Streptococcus dysgalactiae (GCS/GGS), also cause NSTI, with higher fatality rates in this study.

Area of Science:

  • Infectious Diseases
  • Microbiology
  • Epidemiology

Background:

  • Streptococcus pyogenes (group A Streptococcus, GAS) is a primary cause of necrotizing soft tissue infections (NSTI).
  • Other beta-hemolytic streptococci, specifically Streptococcus dysgalactiae subsp. equisimilis (GCS/GGS), can also cause NSTI, but their role is less understood.
  • This study investigates the clinical and molecular aspects of NSTI caused by GAS and GCS/GGS in western Norway.

Purpose of the Study:

  • To characterize the clinical and molecular features of NSTI caused by GAS and GCS/GGS.
  • To compare the epidemiology, clinical presentation, and outcomes of NSTI between GAS and GCS/GGS infections.
  • To identify risk factors for mortality in patients with streptococcal NSTI.

Main Methods:

  • Retrospective analysis of clinical data from 70 NSTI cases between 2000-2009 in western Norway.
  • Bacterial isolates were emm typed and screened for streptococcal superantigen genes.
  • Comparison of clinical characteristics and outcomes between GAS and GCS/GGS infections.

Main Results:

  • A total of 70 NSTI cases were identified, with GAS accounting for 61 and GCS/GGS for 9 cases.
  • In-hospital case fatality rates were 11% for GAS and 33% for GCS/GGS.
  • GCS/GGS patients were older, had more comorbidities, and presented with more superficial disease compared to GAS patients.
  • Predominant GAS emm types were emm1, emm3, and emm4, with virulence gene profiles correlating to emm type.
  • The Laboratory Risk Indicator for Necrotizing Fasciitis score was not consistently high in affected patients.

Conclusions:

  • Streptococcal NSTI is frequent in the studied community.
  • GCS/GGS infections contribute to the NSTI burden and are associated with higher mortality than GAS infections.
  • Differences in predisposing factors and disease characteristics exist between GAS and GCS/GGS NSTI.
  • High age and toxic shock syndrome are significant predictors of mortality in streptococcal NSTI.
Keywords:
Streptococcus dysgalactiae subsp. equisimilisStreptococcus pyogenesemm geneinvasivenecrotizing fasciitisnecrotizing soft tissue infectionssuperantigensβ-haemolytic streptococci

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