MedCompanion

Streptococcus pneumoniae

Pneumococcus

Morphology: Lancet-shaped diplococci, alpha-hemolytic, optochin-sensitive, bile-soluble.

StrepGramPosOther

Typical drugs

  1. #1Amoxicillin— Outpatient CAP.
  2. #2Ceftriaxone— Hospitalized CAP / meningitis.
  3. #3Azithromycin— Combo with β-lactam in severe CAP.

Empiric therapy when resistant

Macrolide-resistance is rising — avoid azithromycin monotherapy for severe CAP. PCN-resistant strains usually still susceptible to ceftriaxone; meningitis dose adds vancomycin until susceptibilities back.

Resistance mechanisms

  • Target alteration

    Altered penicillin-binding proteins (PBPs)

    Example: PCN-resistant pneumococcus

Resistance notes

Vaccine (PCV13/PCV20) reduced invasive disease; non-vaccine serotypes emerging.

Common syndromes

Pearls

Most common cause of bacterial CAP. Splenectomy / sickle cell — encapsulated organism risk.

References

  • IDSA/ATS CAP (2019)