Pseudomonas aeruginosa
One-Sentence Definition
Pseudomonas aeruginosa is an oxidase-positive Gram-negative non-fermenter that thrives in moist environments and causes opportunistic infections with frequent MDR phenotypes and biofilm-associated disease.
Taxonomy & Morphology
- Gram-negative rod; non-lactose fermenter
- Grape-like odor; blue-green pigments (pyocyanin/pyoverdine) classic
- Gram Stain: pink rods
Virulence Highlights
- Biofilm (CF airways, devices)
- Exotoxins (ExoS/ExoT/ExoU via T3SS), elastases, pigments
- Intrinsic impermeability + efflux
Clinical Syndromes
- VAP, burn wound infection, otitis externa (malignant in diabetics)
- Bacteremia in neutropenic/hospitalized patients
- Chronic CF lung infection
Diagnosis
- Culture on standard media; oxidase-positive ID
- AST mandatory for therapy
- Molecular panels may include Pseudomonas targets
Treatment Notes (conceptual)
- Antipseudomonal β-lactams / fluoroquinolones / aminoglycosides per AST and syndrome
- Combination therapy sometimes used in severe disease — practice varies
- Biofilm/device infections need source control
AMR
- Intrinsic resistance high baseline
- Acquired: carbapenemases, upregulated efflux, porin (OprD) loss
- Difficult-to-treat resistance (DTR) category in modern stewardship language
Related Notes
- Biofilm · Bacterial Plasma Membrane · MOC - Antimicrobial Resistance (AMR)
- MOCs: MOC - Bacteriology · MOC - Clinical Microbiology · MOC - Antimicrobials
Active Recall
- Why is Pseudomonas often multidrug-resistant even before treatment?
- Name two classic clinical niches.
- How do biofilms change expected antibiotic response?