USMLE

Pseudomonas aeruginosa: Overview

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Bacteria - Gram Negative
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  2. Neisseria gonorrhoeae
  3. Neisseria meningitidis
  4. Haemophilus influenzae
  5. Bordetella pertussis
  6. Brucella
  7. Legionella pneumophila
  8. Pseudomonas aeruginosa: Overview
  9. Pseudomonas aeruginosa: Disease
  10. Salmonella Overview
  11. Salmonella typhi
  12. Salmonella enteritidis
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  15. Escherichia coli: Overview
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  21. Helicobacter pylori
  22. Borrelia burgdorferi (Lyme Disease)
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  25. Treponema pallidum: Diagnosis
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  30. Rickettsia rickettsii
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  32. Anaplasma vs. Ehrlichia
  33. Coxiella burnetii (Q fever)

Summary

Pseudomonas aeruginosa are gram-negative, rod-shaped, and encapsulated bacteria, with colonies that have a grape-like odor. Pseudomonas is also catalase and oxidase positive. Virulence factors of this bacteria include its production of Exotoxin A, which inhibits elongation factor 2 via ADP ribosylation. Another virulence factor produced by Pseudomonas aeruginosa are pyoverdine and pyocyanin, blue-green pigments that help the bacteria scavenge iron from its local environment.

Key Points

  • Pseudomonas aeruginosa overview 
    • Characteristics
      • Gram negative rod
        • Have a motile appearance on microscopy
      • Oxidase +
      • Encapsulated
        • Higher risk of severe infection in asplenic patients (prior surgery, sickle cell)
      • Catalase +
      • Non-lactose fermenting
      • Has a grape-like odor
      • Aerobic
      • Biofilm formation may contribute to pneumonia in cystic fibrosis
    • Virulence Factors
      • Exotoxin A
        • inactivates EF-2 (elongation factor) via ADP ribosylation
        • inhibits protein synthesis at the ribosome, since EF-2 is needed to translocate tRNA to allow peptide elongation
        • Similar mechanism to diphtheria toxin (Corynebacterium diphtheriae)
      • Pyoverdine and pyocyanin
        • blue-green pigment often seen on microscopy
        • Generates reactive oxygen species
      • Phospholipase C
        • Breaks down phospholipids to degrade cell membranes
      • Endotoxin
        • Causes fever, shock, and DIC in patients
        • Seen in all gram-negative bacteria due to LPS in the bacterial membrane
      • Elastase
        • Breaks down elastin
        • Important for blood vessel and connective tissue destruction (e.g. ecthyma gangrenosum)