Streptococcus

Microbiology

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

Species

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