II. Pathophysiology
- Pseudomonas Aeruginosa (previously P. Pyocyaneus)
- Aerobic, Gram Negative Rods
- Motile, non spore forming, non-lactose producing Bacteria
- Alginate polymer capsule shields P. aeruginosa from Phagocytosis by immune cells (e.g. Macrophages)
- Produces a fluorescent green pigment (pyorubin or pyoverdin) and a blue pigment (pyocyanin)
- Fluorescein stain used in Corneal Abrasion detection is derived from pyorubin
- Lends infected wounds a blue-green discharge and a sweet grape-like scent
- Blue-Green bandage discoloration first described by French pharmacist Carle Gessard in 1882
- Species name aeruginosa is derived from the latin word aerugo ("rusted Copper")
- Previously thought to be an obligate aerobe, but can survive also in anaerobic conditions
- Found in soil and water and has minimal nutrient requirements
- Grows in warm moist environments (esp. in contact with plastic or Rubber)
- Among skin flora in healthy patients
- However, P. Aeruginosa has weak invasive potential in the immunocompetent (without open wounds)
- Opportunistic, life threatening, multi-drug resistant infections in high risk patients
- Exotoxin A (PE)
- Inhibits Protein synthesis in cells (similar to Diphtheria toxin)
- Enters cells via receptor-mediated endocytosis
- Cellular protease breaks extotoxin A into 2 fragments
-
Antibiotic Resistance Mechanisms
- Permeability mutations
- Outer membrane porin loss
- Efflux pumps
- Beta Lactamase
- Primarily AmpC production
- Gyrase Mutations
- Fluoroquinolone resistance
- Permeability mutations
III. Associated Conditions
-
Pneumonia
- Ventilator-Associated Pneumonia
-
Cystic Fibrosis
Pneumonia
- Pseudomonas Aeruginosa colonizes the respiratory tract of Cystic Fibrosis patients
- Osteomyelitis
- Infected Burn Injury
-
Nosocomial Fever and Sepsis
- Associated with colonized tubes, Lines and catheters
- Ventilator-Associated Pneumonia
- Urinary Catheter associated Urinary Tract Infection (CAUTI)
- Intubation Associated Sinusitis
- Urinary Tract Infections
-
Bacterial Endocarditis
- Intravenous Drug Abuse (esp. right-sided Heart Valve endocarditis)
- Skin and Nail Infections
- Malignant Otitis Externa due to Pseudomonas aeruginosa
- Pseudomonas Folliculitis
- Pseudomonas Nail Infection
- Corneal Abrasion Infections (esp. Contact Lens wear)
- Ecthyma Gangrenosum
- Deep Skin Ulcers from hematogenous Pseudomonas seeding in neutropenic patients
IV. Management: Antipseudomonal Antibiotics
- Intravenous Empiric Pseudomonas Coverage (before culture and sensitivity available)
- Piperacillin-Tazobactam (Zosyn)
- Ceftazidime (Fortaz)
- Cefepime
- Meropenem
- Ceftolozane-Tazobactam
- Intravenous Empiric Antibiotics for Severe beta-lactam allergy (e.g. Anaphylaxis)
- Oral Antibiotics with Antipseudomonal Activity
V. References
- (2025) Sanford Guide, accessed 2/1/2025
- Gladwin, Trattler and Mahan (2014) Clinical Microbiology, Medmaster, Fl, p. 92-3
- Diggle (2020) Microbiology 166(1):30-3 +PMID: 31597590 [PubMed]
- Qin (2022) Signal Transduct Target Ther 7(1):199 +PMID: 35752612 [PubMed]