Streptococcus Pneumoniae

Aka: Streptococcus Pneumoniae, Pneumococcus, Diplococcus Pneumoniae

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II. Pathophysiology

  1. Characteristics
    1. No Lancefield Group assigned
    2. Gram Positive Cocci in Pairs (Diplococcus)
    3. Alpha-hemolytic Streptococcus
  2. Virulence Factors
    1. Polysaccharide Capsule protects it from Phagocytosis
    2. With infection, antibodies develop to capsule, but only protect against one of 84 serotypes
      1. Vaccines are polyvalent (21 of the most virulent serotypes as of 2024)
  3. Infections
    1. Penicillin Resistant Pneumococcus
    2. Bacterial Pneumonia (Pneumococcal Pneumonia)
    3. Bacterial Meningitis (Pneumococcal Meningitis)
    4. Otitis Media

III. Labs

  1. Microscopy
    1. Gram Positive Cocci in Pairs
    2. Alpha-hemolytic Streptococcus (like Viridans Streptococcus)
      1. Green coloration on Blood agar plate (BAP)
  2. Differentiated from Viridans Streptococcus (also Alpha-hemolytic Streptococcus)
    1. Quellung Reaction (Neufeld reaction)
      1. Bacterial slide mixed with capsular antibodies and methylene blue
      2. Pneumococcal capsule swells in response to specific antibodies
    2. Bile solubility (10% deoxycholate)
      1. Streptococcus Pneumoniae dissolves in bile acids, while Viridans remains intact
    3. Optochin or "P" disc susceptibility (ethylhydrocupreine hydrochloride impregnated plate)
      1. Streptococcus Pneumoniae growth is inhibited by Optochin

IV. Prevention

  1. See Pneumococcal Vaccine

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