Hemolysis

Overview

• Some bacteria cause hemolysis (breakdown of RBCs) when grown on blood agar
  • the type of hemolysis present can be used to classify the bacteria
• Alpha hemolysis
  • dark and greenish
  • “partial” hemolysis
  • bacteria include
    • Streptococcus pneumoniae
      • Optochin sensitive 
    • Viridans group streptococci
      • Optochin resistant
• Beta hemolysis
  • transparent
  • “complete” hemolysis
  • bacteria include
    • Staphylococcus aureus
    • Streptococcus pyogenes (group A strep)
    • Streptococcus agalactiae (group B strep)
    • Listeria monocytogenes
• Gamma hemolysis
  • unchanged
  • “no hemolysis”
  • bacteria include
    • Enterococcus faecalis (group D strep)
      • can also be alpha hemolytic
• Notice that hemolysis is generally used to distinguish strains of Streptococcus, but that Staphylococcus aureus and Listeria also have characteristic hemolytic properties