Infectious disease · USMLE Step 1 and Step 2

Streptococcus pneumoniae song

Streptococcus pneumoniae - Diagnosis & Vaccination, as a song. Hear the short teaser here. The full song is on YouTube and Spotify.

Streptococcus pneumoniae

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Key points in this song10

Streptococcus pneumoniae is an alpha-hemolytic, gram-positive diplococcus that is optochin-sensitive and bile-soluble, distinguishing it from viridans streptococci.
It is the most common cause of community-acquired pneumonia, bacterial meningitis, and otitis media in adults, and the most common cause of meningitis in adults and the elderly.
The polysaccharide capsule is its key virulence factor, enabling evasion of phagocytosis; anticapsular antibodies are the primary mechanism of host defense.
Asplenic patients (including those with sickle cell disease) are at highest risk for overwhelming S. pneumoniae sepsis due to impaired opsonization and loss of splenic phagocytosis.
Pneumococcal pneumonia classically presents with a single rigor, rust-colored sputum, lobar consolidation on chest X-ray, and fever — distinguishing it from atypical pneumonia.
S. pneumoniae meningitis classically shows CSF with low glucose, high protein, and neutrophilic pleocytosis; empiric treatment is ceftriaxone plus vancomycin plus dexamethasone.
The quellung reaction — capsular swelling upon exposure to type-specific antisera — is the classic identification test for S. pneumoniae.
Penicillin resistance in S. pneumoniae is mediated by mutations in penicillin-binding proteins (PBPs), not beta-lactamase production.
Two vaccines are available: PCV15/PCV20 (conjugate, T-cell dependent, preferred for children and immunocompromised) and PPSV23 (polysaccharide, T-cell independent, used in adults ≥65 and high-risk groups).
S. pneumoniae is the most common cause of secondary bacterial pneumonia following influenza virus infection.