Pseudomonas infection (Pseudomonas aeruginosa)
๐ About
- Pseudomonas aeruginosa โ an opportunistic pathogen mainly affecting immunocompromised patients (HIV/AIDS, chemotherapy, transplant, cystic fibrosis).
- Important cause of nosocomial infections worldwide.
๐ฌ Characteristics
- Gram-negative, strictly aerobic bacillus (rod).
- Motile (flagella), but usually non-capsulated.
- Grows easily on simple media; produces pigments (e.g. pyocyanin โ blue-green colour and fruity odour).
๐งฌ Virulence Factors
- Elastases โ break down elastin, damaging tissues & blood vessels.
- IgA protease โ degrades mucosal IgA, evading immune defences.
- Biofilm formation (esp. in CF patients) โ antibiotic resistance & chronic infection.
- Exotoxin A โ inhibits protein synthesis, leading to host cell death (similar to diphtheria toxin).
๐ Source
- Environmental organism: found in water, soil, sinks, humidifiers, and hospital surfaces.
- Spread in hospitals ๐ฅ via contaminated equipment, catheters, or poor hygiene practices.
โ ๏ธ Pathogenicity
- Skin infections: Burn wounds, venous ulcers โ necrotic, invasive infection.
- Respiratory infections: CF, bronchiectasis, COPD โ chronic colonisation & pneumonia.
- Urinary tract infections: Associated with catheters in inpatients.
- Ear infections: Otitis externa, including โswimmerโs earโ.
- Eye infections: Keratitis, endophthalmitis after trauma/contact lenses.
- Sepsis: Can progress to bacteraemia with high mortality.
๐ Investigations
- Microscopy & culture โ characteristic colonies (blue-green pigment, fruity odour).
- Serotyping or PCR โ epidemiology & outbreak tracking.
๐ Antibiotic Resistance
- Highly resistant to many antibiotics.
- Resistance via: ฮฒ-lactamases, efflux pumps, porin mutations, biofilm protection.
๐ฉบ Management
- Antibiotics: Combination therapy often needed, tailored to sensitivity testing.
- Piperacillinโtazobactam
- Meropenem
- Ceftazidime (3rd-gen cephalosporin)
- Ciprofloxacin (quinolone)
- Aminoglycosides (gentamicin, tobramycin)
- Infection control: Early isolation & strict hygiene to prevent spread in hospital wards.
๐ก๏ธ 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.
โ ๏ธ Exam pearl: *Pseudomonas aeruginosa* โ blue-green colonies, fruity odour, opportunistic infection (CF lungs, burns, catheter UTIs). Intrinsically resistant โ requires sensitivity-guided, often combination therapy.
