Staphylococcus – Hemolysis

  • Some bacteria produce hemolysins, exotoxins that cause red blood cells (RBC’s) to burst open (hemolyse).When these bacteria are cultured on blood agar, this hemolysis is visible as an area of clearing around the colony (zone of hemolysis).
  • If the organism produces enzymes that completely lyse the RBC’s, this is termed beta hemolysis. Partial destruction of the RBC’s produces a greenish color to the zone of hemolysis and is termed alpha hemolysis.
  • Organisms lacking hemolysins cause no change in the color or opacity of the media and are termed gamma hemolysis.
  • Production of hemolysins is associated with virulence. Streptococcus pneumoniae, the major cause of community-acquired bacterial pneumonia is alpha-hemolytic, while Streptococcus pyogenes (Group A Strep) is beta-hemolytic. Staphylococcus aureus is usually beta-hemolytic.
Staphylococcus - Hemolysis

Staphylococcus – Hemolysis

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