Streptococcus

Microbiology

• Catalase negative Gram-positive coccus in pairs or chains
• Two orthogonal classifications
  • Hemolytic properties on blood agar
    • Alpha: incomplete hemolysis (appears green)
    • Beta: complete hemolysis (appears clear)
    • Gamma: no hemolysis
  • Lancefield antigen group (A-H)

Species

• Alpha-hemolytic
  • Streptococcus pneumoniae (usually in pairs)
  • Viridans group streptococci
    • Streptococcus mitis
    • Streptococcus oralis
    • Streptococcus mutans
    • Streptococcus sanguinis
    • Streptococcus sobrinus
    • Streptococcus anginosus group
      • Streptococcus anginosus
      • Streptococcus constellatus
      • Streptococcus intermedius
• Beta-hemolytic
  • Group A: Streptococcus pyogenes
  • Group B: Streptococcus agalactiae
  • Group G: Streptococcus dysgalactiae
  • Non-Lancefield: Streptococccus iniae
• Gamma-hemolytic
  • Group D streptococci
    • Streptococcus bovis
    • Previously, Enterococcus spp.