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Streptococci
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Streptococci

Streptococcus pyogenes Streptococcal agalactiae Enterococci faecalis and Enterococci faecium Viridans group streptococci Streptococcus pneumoniae
Streptococci classification:
  • Hemolysis of blood agar:
– Alpha-hemolytic species incompletely lyse red blood cells; this casts a greenish hue around the bacteria, which include Viridans group and S. pneumoniae. – Beta-hemolytic streptococci completely lyse red blood cells, which produces a clear outline around the bacteria; this group includes S. pyogenes and S. agalactiae. – Gamma-hemolytic streptococci do not lyse red blood cells; thus, there is no outline around the bacteria. This group includes the Enterococci.
  • Lancefield Serologic groupings categorize the beta-hemolytic streptococci based upon the C-carbohydrates in their cell walls.
References
Hemolysis on blood agar (https://www.britannica.com/science/hemolysis; Y tambe).

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