Typical Pneumonia

Question 1

Compare the features of “typical” and “atypical” pneumonias.

Answer 1

• Typical: high fever, shaking chills, chest pain
  
  • lobar consolidation on X-ray
• Atypical: less severe illness (“walking pneumonia”)
  
  • Dry cough, headache, and other systemic complains,
  • X-ray -diffuse pattern, looks worse than illness suggests.

Question 2

Cite the major causes of acute, community-acquired “typical” pneumonia and acute “hospital acquired” pneumonia.

Answer 2

Typical: 
-Streptococcus pneumoniae (most common cause of acute community acquired pneumonia or CAP)
-Staphylococcus aureus-CAP
-Haemophilus influenzae-CAP
-Gram-negative enterics (hospital acquired) 
Atypical: 
-Mycoplasma pneumoniae
-Chlamydia pneumoniae, psittaci
-Legionella pneumophila
-Influenza and other viruses
-Coxiella burnetti

Question 3

microbiological characteristics of Streptococcus pneumoniae.
How is the organism is identified in the laboratory?

Answer 3

Morphology/growth:

• alpha hemolytic (not true lysis; rather, green color is due to due to breakdown of hemoglobin by pneumolysin)
• Colonies are mucoid due to capsule
• Gram positive lancet shaped cocci
• Catalase negative
• best growth on media with 5-10% blood;
• autolytic enzymes cause lysis of colony in bile salts (“bile solubility”)
• susceptibility to optochin

Question 4

Name the major virulence determinant of Streptococcus pneumoniae

Answer 4

Capsular Polysaccharides:
-Capsule interferes with the deposition of C3b on the bacterial surface
-Therefore, no recognition of C3b-coated organisms by the complement receptors on phagocytes
~90 serotypes;
-anti-capsular antibody provides type-specific immunity
-Loss of capsule=loss of virulence
Surface proteins:
-prevent the activation of complement
Pili:
-Enable S. pneumoniae to attach to epithelial cells in the upper respiratory tract

Question 5

Streptococcus pneumoniae Clinical manifestations

Answer 5

-sudden onset of chills
-fever
-pleuritic pain
-rusty sputum/positive blood cultures in 30% of cases.
Possible complications:
-Direct – lung abscess
-Via blood:
-empyema
-pericarditis
-meningitis
-intrapleural abscess
-septic arthritis

Question 6

Therapy for S. pneumonia ND Pneumococccal Infections

Answer 6

• Many isolates of S. pneumoniae are now penicillin resistant.
• Guidelines for empiric treatment change over time.
• Different regimens are recommended for different types of pneumococcal infections.

Question 7

Composition of the two major types of pneumococcal vaccines and the intended recipients of each.

Answer 7

-Conjugate Vaccine (PCV13)
-PCV13 was approved for use among children aged 6 weeks–71 months and succeeds PCV7, which was licensed by FDA in 2000
-Older vaccine: polysaccharide only vaccine (23 PS)
-Contains capsular polysaccharide from each of 23 serotypes.
-Currently recommended for everyone at 65
≥19 years immunocompromising conditions, functional or anatomic asplenia, CSF leaks, or cochlear implants
should receive a dose of PCV13 first, followed by a dose of PPSV23 at least 8 weeks later