Updated: 10/12/2019

Streptococcus pneumoniae

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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
 

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(M1.MC.15.75) A 70-year-old male presents with signs and symptoms consistent with community acquired pneumonia. A sputum sample is obtained, and the Gram stain is shown in Figure A. What type of vaccine could have been administered to prevent this patient's illness? Tested Concept

QID: 106715
FIGURES:
1

Monosaccharide conjugate

20%

(13/66)

2

Polysaccharide

55%

(36/66)

3

Inactivated

3%

(2/66)

4

Live attenuated

12%

(8/66)

5

Toxoid

5%

(3/66)

L 3 D

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(M1.MC.15.74) An 84-year-old female presents to the emergency department from her nursing home with complaints of fever and a productive cough with rust-colored sputum that has developed over the last 2 days. She also endorses shortness of breath and severe fatigue. Her vital signs are as follows: T 38.5 C, HR 98, BP 110/66, RR 18, SpO2 94% on room air. Physical examination is significant for decreased breath sounds and crackles over the the right middle and lower lobes on auscultation. A chest radiograph is obtained and is shown in Figure A. A sputum sample is also collected for gram stain and culture, with the results of the gram stain shown in Figure B. Which of the following is the primary virulence factor of the infecting pathogen in this patient's presentation? Tested Concept

QID: 106701
FIGURES:
1

IgA protease

19%

(32/168)

2

Exotoxin production

8%

(13/168)

3

M-protein

14%

(24/168)

4

Polysaccharide capsule

53%

(89/168)

5

Lipopolysaccharide

4%

(6/168)

L 1 D

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(M1.MC.15.75) A 60-year-old man presents with fever and cough productive of rust-colored sputum and is diagnosed with community acquired pneumonia. The causative organism is isolated, and a Gram stain is shown in Figure 1. Which of the following most correctly describes additional features of the most likely causative organism? Tested Concept

QID: 106709
FIGURES:
1

Catalase positive, alpha hemolytic, optochin sensitive

8%

(18/236)

2

Catalase positive, beta hemolytic, optochin sensitive

6%

(15/236)

3

Catalase negative, alpha hemolytic, optochin sensitive

66%

(156/236)

4

Catalase negative, beta hemolytic, optochin sensitive

12%

(28/236)

5

Catalase negative, alpha hemolytic, optochin resistant

6%

(15/236)

L 1 D

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(M1.MC.12.8) While testing various strains of Streptococcus pneumoniae, a researcher discovers that a certain strain of this bacteria is unable to cause disease in mice when deposited in their lungs. What physiological test would most likely deviate from normal in this strain of bacteria as opposed to a typical strain? Tested Concept

QID: 101467
1

Bile solubility

6%

(5/77)

2

Optochin sensitivity

19%

(15/77)

3

Quellung reaction

48%

(37/77)

4

Hemolytic reaction when grown on sheep blood agar

10%

(8/77)

5

Motility

10%

(8/77)

L 1 B

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