Streptococcus pneumoniae

Snapshot

• A 56-year-old man presents to the emergency department for a severe headache, generalized malaise, and fatigue. Her symptoms are associated with neck stiffness and nausea. Physical examination is significant for nuchal rigidity and an inability to extend at the knee while the hips are flexed at 90°. A lumbar puncture is performed and cerebral spinal fluid studies demonstrate an elevated opening pressure, elevated protein, decreased glucose, and a leukocytosis. Gram stain of the cerebral spinal fluid demonstrates lancet-shaped, gram-positive cocci.

Introduction

• Classification
  • lancet-shaped, gram-positive cocci that are
    • α-hemolytic
    • encapsulated
    • optochin sensitive  
    • quellung reaction positive  
    • contain IgA protease
• Epidemiology
  • incidence
    • adults
      • the most common cause of pneumonia and meningitis
    • children
      • the most common cause of otitis media
• Pathogenesis
  • contains a polysaccharide capsule that protects it from phagocytosis
    • contains the ability to adhere and form a robust biofilm in the nasopharynx, sinuses, and inner ear
      • after epithelial invasion, an inflammatory host immune response ensues
• Associated conditions
  • meningitis
  • otitis media 
  • pneumonia
• sepsis

Presentation

• Symptoms
  • meningitis
    • headache
    • neck stiffness
  • otitis media
    • inner ear pain
  • pneumonia
    • shortness of breath
    • productive cough
    • pleuritic chest pain
• Physical exam
  • meningitis
    • nuchal rigidity
    • Bruzinski sign
      • neck flexion leads to flexing of the knees while the patient is supine
    • Kernig sign
      • extension of the knee while the hips are flexed at 90° causes pain/discomfort
  • otitis media
    • fever
    • irritability
    • ear-tugging/rubbing
  • pneumonia 
    • decreased breath sounds
    • increased fremitus
    • dullness to percussion
• rales

Studies

• Gram stain and culture
  • sputum
  • cerebral spinal fluid
• blood

Differential

• Other causes of meningitis
  • N. meningitidis
    • gram-negative diplococci
  • L. monocytogenes
    • gram-positive rods
• Other causes of otitis media 
  • M. catarrhalis
    • gram-negative diplococci
• Other causes of pneumonia
• respiratory viruses

Treatment

• Preventative
  • pneumococcal vaccine 
    • indication
      • pneumococcal polysaccharide vaccine (PPV) 
      • pneumococcal capsular vaccine (PCV)
• Medical
  • penicillin, a penicillin derivative, or a 3rd generation cephalosporin
    • indication
      • in penicillin-susceptible pneumococci causing pneumonia
    • comments
      • penicillin-resistant strains are treated with vancomycin
  • amoxicillin or amoxicillin-clavulanate
    • indication
      • in acute otitis media
  • ceftriaxone and vancomycin
    • indication
• to cover S. pneumonia, N. meningitidis, and H. influenzae as a cause of meningitis

Complications

• Septic shock