Genus Streptococcus

Genus Streptococcus has a characteristic feature with a of a gram positive cocci in short or long chain. It grows best on blood agar plate in order to see the ability to hemolyze blood serves to differentiate the species.


  1. Through clinical presentation
    • Pyogenic streptococci
    • Oral streptococci
    • Intestinal streptococci
  2. Serologic Properties – This is developed by Lancefield in 1933 for differentiating pathogenic B-hemolytic strains. Most B-hemolytic strains and some alpha and nonhemolytic strains possess group specific antigens, which are aither C-carbohyradte or teichoic acids (cell wall components).
    • Group A – Streptococcus pyogenes
    • Group B – Streptococcus agalactiae
    • Group D / Viridans group – consists of two subgroups:
      • Enterococcus/ intestinal streptococci
      • Nonenterococcal/oral streptococci

Hemolytic Patterns on Blood Agar Plate

  1. Hemolytic streptococci or green streptococci – Produce a substance called ?-hemolysin that recudes haemoglobin (red coloring pigment of the blood) to methemoglobin (green); this reduction causes a greenish zone to surround the colony.
  2. Haemolytic streptococci – produce a hemolysin that forms a clear zone of hemolysis on blood agar. Species producing this pattern is the streptococcus pyogenes or Group A streptococcus considered as the most pathogenic.
  3. Haemolytic streptococci – produce no apparent effect on red blood cells. It is also known as non-haemolytic streptococci or streptococcus non-hemolyticus

Biochemical (physiologic) Properties

  1. Streptococcus pyogenes
  2. S. Agalactiae
  3. S. Equisimilis
  4. Enterococcus faecalis
  5. E. Faecium
  6. S. Bovis
  7. S. Milleri group
  8. S. Pneumoniae
  9. S. Salivarius
  10. S. Sanguis
  11. S. Mutans
  12. S. Acidominimus
  13. S. Uberis
  14. S. Mitis

Pathogenic Species:

These are medically important.

  1. Streptococcus pneumonia
  2. Streptococcus pyogenes
  3. Streptococcus agalactiae
  4. Viridans streptococci

Daisy Jane Antipuesto RN MN

Currently a Nursing Local Board Examination Reviewer. Subjects handled are Pediatric, Obstetric and Psychiatric Nursing. Previous work experiences include: Clinical instructor/lecturer, clinical coordinator (Level II), caregiver instructor/lecturer, NC2 examination reviewer and staff/clinic nurse. Areas of specialization: Emergency room, Orthopedic Ward and Delivery Room. Also an IELTS passer.

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