Makindo Medical Notes

📖 About

• Pseudomonas aeruginosa → an opportunistic pathogen mainly affecting immunocompromised patients (HIV/AIDS, chemotherapy, transplant, cystic fibrosis).
• Important cause of nosocomial infections worldwide.

🔬 Characteristics

• Gram-negative, strictly aerobic bacillus (rod).
• Motile (flagella), but usually non-capsulated.
• Grows easily on simple media; produces pigments (e.g. pyocyanin → blue-green colour and fruity odour).

🧬 Virulence Factors

• Elastases → break down elastin, damaging tissues & blood vessels.
• IgA protease → degrades mucosal IgA, evading immune defences.
• Biofilm formation (esp. in CF patients) → antibiotic resistance & chronic infection.
• Exotoxin A → inhibits protein synthesis, leading to host cell death (similar to diphtheria toxin).

🏠 Source

• Environmental organism: found in water, soil, sinks, humidifiers, and hospital surfaces.
• Spread in hospitals 🏥 via contaminated equipment, catheters, or poor hygiene practices.

⚠️ Pathogenicity

• Skin infections: Burn wounds, venous ulcers → necrotic, invasive infection.
• Respiratory infections: CF, bronchiectasis, COPD → chronic colonisation & pneumonia.
• Urinary tract infections: Associated with catheters in inpatients.
• Ear infections: Otitis externa, including “swimmer’s ear”.
• Eye infections: Keratitis, endophthalmitis after trauma/contact lenses.
• Sepsis: Can progress to bacteraemia with high mortality.

🔎 Investigations

• Microscopy & culture → characteristic colonies (blue-green pigment, fruity odour).
• Serotyping or PCR → epidemiology & outbreak tracking.

💊 Antibiotic Resistance

• Highly resistant to many antibiotics.
• Resistance via: β-lactamases, efflux pumps, porin mutations, biofilm protection.

🩺 Management

• Antibiotics: Combination therapy often needed, tailored to sensitivity testing.
  • Piperacillin–tazobactam
  • Meropenem
  • Ceftazidime (3rd-gen cephalosporin)
  • Ciprofloxacin (quinolone)
  • Aminoglycosides (gentamicin, tobramycin)
• Infection control: Early isolation & strict hygiene to prevent spread in hospital wards.

🛡️ Prevention

• Strict hand hygiene & sterilisation of equipment.
• Limit catheter use & remove promptly when no longer required.
• Use of PPE & isolation rooms in outbreaks.
• Regular cleaning of hospital water systems & sinks.

⚠️ Exam pearl: *Pseudomonas aeruginosa* → blue-green colonies, fruity odour, opportunistic infection (CF lungs, burns, catheter UTIs). Intrinsically resistant → requires sensitivity-guided, often combination therapy.