Updated: 1/21/2019

Streptococcus pneumoniae

Topic
Review Topic
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Questions
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Evidence
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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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Questions (7)
Lab Values
Blood, Plasma, Serum Reference Range
ALT 8-20 U/L
Amylase, serum 25-125 U/L
AST 8-20 U/L
Bilirubin, serum (adult) Total // Direct 0.1-1.0 mg/dL // 0.0-0.3 mg/dL
Calcium, serum (Ca2+) 8.4-10.2 mg/dL
Cholesterol, serum Rec: < 200 mg/dL
Cortisol, serum 0800 h: 5-23 μg/dL //1600 h:
3-15 μg/dL
2000 h: ≤ 50% of 0800 h
Creatine kinase, serum Male: 25-90 U/L
Female: 10-70 U/L
Creatinine, serum 0.6-1.2 mg/dL
Electrolytes, serum  
Sodium (Na+) 136-145 mEq/L
Chloride (Cl-) 95-105 mEq/L
Potassium (K+) 3.5-5.0 mEq/L
Bicarbonate (HCO3-) 22-28 mEq/L
Magnesium (Mg2+) 1.5-2.0 mEq/L
Estriol, total, serum (in pregnancy)  
24-28 wks // 32-36 wks 30-170 ng/mL // 60-280 ng/mL
28-32 wk // 36-40 wks 40-220 ng/mL // 80-350 ng/mL
Ferritin, serum Male: 15-200 ng/mL
Female: 12-150 ng/mL
Follicle-stimulating hormone, serum/plasma Male: 4-25 mIU/mL
Female: premenopause: 4-30 mIU/mL
midcycle peak: 10-90 mIU/mL
postmenopause: 40-250
pH 7.35-7.45
PCO2 33-45 mmHg
PO2 75-105 mmHg
Glucose, serum Fasting: 70-110 mg/dL
2-h postprandial:<120 mg/dL
Growth hormone - arginine stimulation Fasting: <5 ng/mL
Provocative stimuli: > 7ng/mL
Immunoglobulins, serum  
IgA 76-390 mg/dL
IgE 0-380 IU/mL
IgG 650-1500 mg/dL
IgM 40-345 mg/dL
Iron 50-170 μg/dL
Lactate dehydrogenase, serum 45-90 U/L
Luteinizing hormone, serum/plasma Male: 6-23 mIU/mL
Female: follicular phase: 5-30 mIU/mL
midcycle: 75-150 mIU/mL
postmenopause 30-200 mIU/mL
Osmolality, serum 275-295 mOsmol/kd H2O
Parathyroid hormone, serume, N-terminal 230-630 pg/mL
Phosphatase (alkaline), serum (p-NPP at 30° C) 20-70 U/L
Phosphorus (inorganic), serum 3.0-4.5 mg/dL
Prolactin, serum (hPRL) < 20 ng/mL
Proteins, serum  
Total (recumbent) 6.0-7.8 g/dL
Albumin 3.5-5.5 g/dL
Globulin 2.3-3.5 g/dL
Thyroid-stimulating hormone, serum or plasma .5-5.0 μU/mL
Thyroidal iodine (123I) uptake 8%-30% of administered dose/24h
Thyroxine (T4), serum 5-12 μg/dL
Triglycerides, serum 35-160 mg/dL
Triiodothyronine (T3), serum (RIA) 115-190 ng/dL
Triiodothyronine (T3) resin uptake 25%-35%
Urea nitrogen, serum 7-18 mg/dL
Uric acid, serum 3.0-8.2 mg/dL
Hematologic Reference Range
Bleeding time 2-7 minutes
Erythrocyte count Male: 4.3-5.9 million/mm3
Female: 3.5-5.5 million mm3
Erythrocyte sedimentation rate (Westergren) Male: 0-15 mm/h
Female: 0-20 mm/h
Hematocrit Male: 41%-53%
Female: 36%-46%
Hemoglobin A1c ≤ 6 %
Hemoglobin, blood Male: 13.5-17.5 g/dL
Female: 12.0-16.0 g/dL
Hemoglobin, plasma 1-4 mg/dL
Leukocyte count and differential  
Leukocyte count 4,500-11,000/mm3
Segmented neutrophils 54%-62%
Bands 3%-5%
Eosinophils 1%-3%
Basophils 0%-0.75%
Lymphocytes 25%-33%
Monocytes 3%-7%
Mean corpuscular hemoglobin 25.4-34.6 pg/cell
Mean corpuscular hemoglobin concentration 31%-36% Hb/cell
Mean corpuscular volume 80-100 μm3
Partial thromboplastin time (activated) 25-40 seconds
Platelet count 150,000-400,000/mm3
Prothrombin time 11-15 seconds
Reticulocyte count 0.5%-1.5% of red cells
Thrombin time < 2 seconds deviation from control
Volume  
Plasma Male: 25-43 mL/kg
Female: 28-45 mL/kg
Red cell Male: 20-36 mL/kg
Female: 19-31 mL/kg
Cerebrospinal Fluid Reference Range
Cell count 0-5/mm3
Chloride 118-132 mEq/L
Gamma globulin 3%-12% total proteins
Glucose 40-70 mg/dL
Pressure 70-180 mm H2O
Proteins, total < 40 mg/dL
Sweat Reference Range
Chloride 0-35 mmol/L
Urine  
Calcium 100-300 mg/24 h
Chloride Varies with intake
Creatinine clearance Male: 97-137 mL/min
Female: 88-128 mL/min
Estriol, total (in pregnancy)  
30 wks 6-18 mg/24 h
35 wks 9-28 mg/24 h
40 wks 13-42 mg/24 h
17-Hydroxycorticosteroids Male: 3.0-10.0 mg/24 h
Female: 2.0-8.0 mg/24 h
17-Ketosteroids, total Male: 8-20 mg/24 h
Female: 6-15 mg/24 h
Osmolality 50-1400 mOsmol/kg H2O
Oxalate 8-40 μg/mL
Potassium Varies with diet
Proteins, total < 150 mg/24 h
Sodium Varies with diet
Uric acid Varies with diet
Body Mass Index (BMI) Adult: 19-25 kg/m2
Calculator

(M1.MC.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? Review Topic

QID: 106715
FIGURES:
1

Monosaccharide conjugate

24%

(4/17)

2

Polysaccharide

53%

(9/17)

3

Inactivated

6%

(1/17)

4

Live attenuated

12%

(2/17)

5

Toxoid

0%

(0/17)

M1

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PREFERRED RESPONSE 2
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(M1.MC.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? Review Topic

QID: 106701
FIGURES:
1

IgA protease

22%

(25/115)

2

Exotoxin production

6%

(7/115)

3

M-protein

15%

(17/115)

4

Polysaccharide capsule

51%

(59/115)

5

Lipopolysaccharide

5%

(6/115)

M1

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(M1.MC.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? Review Topic

QID: 106709
FIGURES:
1

Catalase positive, alpha hemolytic, optochin sensitive

8%

(13/172)

2

Catalase positive, beta hemolytic, optochin sensitive

6%

(11/172)

3

Catalase negative, alpha hemolytic, optochin sensitive

64%

(110/172)

4

Catalase negative, beta hemolytic, optochin sensitive

14%

(24/172)

5

Catalase negative, alpha hemolytic, optochin resistant

7%

(12/172)

M1

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(M1.MC.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? Review Topic

QID: 101467
1

Bile solubility

5%

(1/21)

2

Optochin sensitivity

19%

(4/21)

3

Quellung reaction

33%

(7/21)

4

Hemolytic reaction when grown on sheep blood agar

19%

(4/21)

5

Motility

10%

(2/21)

M1

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