Pseudomonas Aeruginosa

Characteristics/Epidemiology

Pseudomonas aeruginosa - primary human pathogen

Widely distributed in nature

Colonise healthy humans without causing disease

Also opportunistic pathogen, major cause of nosocomial infections

 

Pathogenesis/Transmission

Pili - attachment

Glycocalyx capsule - Antiphagocytic

Also produce

• Extracellular protease (elastase, alkaline protease)
• Cytotoxin (aka leukocidin)
• Hemolysin (phospholipase C, rhamnolipid)
• Pyocyanin
• Endotoxin
• Exotoxin A (inhibit elongation factor)
• Exotoxin S (ADP-ribosylates specific GTP-binding proteins)

Clinical significance

Localised infections

Potential to lead to systemic infections

Can lead to infections in eye, ear, skin, urinary tract, respiratory tract, GIT, CNS.

Systemic infections

• Bacteremia
• Secondary pneumonia (hematologic malignancies)
• Bone and joint infection (IV user,
• Endocarditis (IV user, prosthetic heart valve)
• Skin/soft tissue infections
  Ecthyma gangrenosum (erythematous necrotic lesion)

 

Laboratory identification

Motile (polar flagella)

Encapsulated

Obligately aerobic

Oxidises but does not ferment carbohydrate

Minimal nutritional requirement

Produce diffusible green (pyoverdin) and blue (pyocyanin) pigment

Cultured on MacConkey agar or standard blood agar.

Treatment

Rapid development of resistance

First line: Combination of tobramycin + antipseudomonal penicillin

Antipseudomonal

• Piperacillin
• Ticarcillin
• Ticarcillin + clavulanic acid
• Piperacillin + Taxobactam

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Things to revise/add later:

Bibliography:

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