Watch World’s Best Lecture on Heart Failure – 7 DAYS FREE TRIAL


Streptococcus is a is a genus of coccus (spherical) Gram-positive bacteria and they grow in chains or pairs. Most are oxidase-negative and catalase-negative, and many are facultative anaerobes.


Species of Streptococcus are classified based on their hemolytic properties.

  • Alpha-hemolytic streptococci

    • These cause oxidization of iron in hemoglobin molecules within red blood cells, giving it a greenish color on blood agar.
    • These include following:
      • S. Pneumoniae
      • S. Viridans
  • Beta-hemolytic streptococci

    • These causes complete lysis of red cells in the media around and under the colonies: the area appears lightened (yellow) and transparent.
    • They produce an exotoxin called Streptolysin which is of 2 types.
      • Streptolysin O
      • Streptolysin S
    • These include following:
      • S. Pyogenes 
      • S. Agalactiae
      • S. Zooepidemicus
      • S. Bovis
      • S. Equinus
      • S. Sanguinis
      • S. Suis
      • S. Mitis
      • S. Mutans
      • S. pneumoniae

Watch World’s Best Lecture on Heart Failure – 7 DAYS FREE TRIAL

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