S. Pneumoniae

  1. Morphology
    • Gram positive oval cocci arranged in pairs (lancet/bullet shape)
    • Surface capsule -> polysaccharide polymers (unique for each serotype)
    • Grows on blood agar with alpha-hemolysis
    • bile solubility test
    • Pneumolysin: pore forming toxin
  2. Epidemiology
    • Leading cause of pneumonia, acute purulent meningitis, bacteremia
    • Otitis media
    • Usually in young and older person
    • Usually present in nasopharynx
  3. Pathogenesis
    • Aspiration of respiratory secretions containing the bacteria
    • COPD, respiratory dysfunction from alcoho, narcotics, trauma, etc increase the risk of infection
    • Alveolar infection: surface capsule blocks phagocytosis via complement inhibition; pneumolysin damages tissue
    • Capsule: Major determinant of virulence
    • Pneumolysin: destroys respiratory epi cells which aids in reaching the alveolus
    • Immunity: type specific
  4. Clinical manifestations
    • Pneumonia: Shaking chill and high fever, cough with rusty sputum, pleurotic chest pain; lobar consolidation
    • meningitis: most common at advanced age
    • Does not cause pharyngitis or tonsillitis
  5. Diagnosis
    • Routine culture
    • Susceptibility Optochin
    • Bile solution
    • Blood cultures valuable
  6. Treatment
    • Penicillin G
    • Resistance via changes in transpeptidases
    • Penicillinase not produced
  7. Prevention
    • Conjugate vaccine
    • Adult: 23 serotypes
    • Kids: 13 (below 2 YO)
Card Set
S. Pneumoniae
S. Pneumoniae