Pseudomonas Aeruginosa

Aka: Pseudomonas Aeruginosa, Pseudomonas Pyocyaneus, Antipseudomonal Antibiotic, Anti-Pseudomonal Antibiotic

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II. Pathophysiology

  1. Pseudomonas Aeruginosa (previously P. Pyocyaneus)
    1. Aerobic, Gram Negative Rods
    2. Motile, non spore forming, non-lactose producing Bacteria
    3. Alginate polymer capsule shields P. aeruginosa from Phagocytosis by immune cells (e.g. Macrophages)
  2. Produces a fluorescent green pigment (pyorubin or pyoverdin) and a blue pigment (pyocyanin)
    1. Fluorescein stain used in Corneal Abrasion detection is derived from pyorubin
    2. Lends infected wounds a blue-green discharge and a sweet grape-like scent
    3. Blue-Green bandage discoloration first described by French pharmacist Carle Gessard in 1882
    4. Species name aeruginosa is derived from the latin word aerugo ("rusted Copper")
  3. Previously thought to be an obligate aerobe, but can survive also in anaerobic conditions
  4. Found in soil and water and has minimal nutrient requirements
    1. Grows in warm moist environments (esp. in contact with plastic or Rubber)
  5. Among skin flora in healthy patients
    1. However, P. Aeruginosa has weak invasive potential in the immunocompetent (without open wounds)
  6. Opportunistic, life threatening, multi-drug resistant infections in high risk patients
    1. Cystic Fibrosis
    2. Burn Injury
    3. Wound Infections
    4. Immunocompromised (e.g. Diabetes Mellitus)
    5. Nosocomial Infection
  7. Exotoxin A (PE)
    1. Inhibits Protein synthesis in cells (similar to Diphtheria toxin)
    2. Enters cells via receptor-mediated endocytosis
    3. Cellular protease breaks extotoxin A into 2 fragments
      1. Binding Protein (28 kDa fragment)
      2. Active Protein (37 kDA fragment)
        1. ADP-ribosylates elongation factor 2 (EF2) in conjunction with NAD+
        2. Halts peptide elongation
  8. Antibiotic Resistance Mechanisms
    1. Permeability mutations
      1. Outer membrane porin loss
      2. Efflux pumps
    2. Beta Lactamase
      1. Primarily AmpC production
    3. Gyrase Mutations
      1. Fluoroquinolone resistance

III. Associated Conditions

  1. Pneumonia
    1. Ventilator-Associated Pneumonia
    2. Cystic Fibrosis Pneumonia
      1. Pseudomonas Aeruginosa colonizes the respiratory tract of Cystic Fibrosis patients
  2. Osteomyelitis
    1. Diabetic Foot Infection
    2. Intravenous Drug Abuse (Vertebral Osteomyelitis, Clavicle Osteomyelitis)
    3. Pseudomonas Osteochondritis (Sweaty Tennis Shoe Syndrome)
  3. Infected Burn Injury
  4. Nosocomial Fever and Sepsis
    1. Associated with colonized tubes, Lines and catheters
    2. Ventilator-Associated Pneumonia
    3. Urinary Catheter associated Urinary Tract Infection (CAUTI)
    4. Intubation Associated Sinusitis
  5. Urinary Tract Infections
    1. Urinary Catheter associated Urinary Tract Infection (CAUTI)
  6. Bacterial Endocarditis
    1. Intravenous Drug Abuse (esp. right-sided Heart Valve endocarditis)
  7. Skin and Nail Infections
    1. Malignant Otitis Externa due to Pseudomonas aeruginosa
    2. Pseudomonas Folliculitis
    3. Pseudomonas Nail Infection
    4. Corneal Abrasion Infections (esp. Contact Lens wear)
    5. Ecthyma Gangrenosum
      1. Deep Skin Ulcers from hematogenous Pseudomonas seeding in neutropenic patients

IV. Management: Antipseudomonal Antibiotics

  1. Intravenous Empiric Pseudomonas Coverage (before culture and sensitivity available)
    1. Piperacillin-Tazobactam (Zosyn)
    2. Ceftazidime (Fortaz)
    3. Cefepime
    4. Meropenem
    5. Ceftolozane-Tazobactam
  2. Intravenous Empiric Antibiotics for Severe beta-lactam allergy (e.g. Anaphylaxis)
    1. Aztreonam
    2. Ciprofloxacin
    3. Levofloxacin
  3. Oral Antibiotics with Antipseudomonal Activity
    1. Ciprofloxacin
    2. Levofloxacin

V. References

  1. (2025) Sanford Guide, accessed 2/1/2025
  2. Gladwin, Trattler and Mahan (2014) Clinical Microbiology, Medmaster, Fl, p. 92-3
  3. Diggle (2020) Microbiology 166(1):30-3 +PMID: 31597590 [PubMed]
  4. Qin (2022) Signal Transduct Target Ther 7(1):199 +PMID: 35752612 [PubMed]

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