This episode examines Pseudomonas and related non-fermenting Gram-negative rods. Drawing from Murray’s Chapter 27, it focuses primarily on Pseudomonas aeruginosa, a metabolically versatile organism defined by environmental resilience and intrinsic antibiotic resistance.

The narrative begins with ecology: P. aeruginosa thrives in moist environments - soil, water, sinks, ventilator tubing - and exploits breaches in host defences. It is not typically a primary pathogen in healthy individuals; instead, it targets the immunocompromised, the critically ill, and those with structural lung disease.

Virulence factors include exotoxin A, elastases, quorum sensing, and robust biofilm formation. Its distinctive pigments (pyocyanin, pyoverdine) and characteristic odour become diagnostic cues. The episode highlights cystic fibrosis lung infection as a model of chronic biofilm persistence.

Resistance mechanisms - efflux pumps, beta-lactamases, permeability changes - are presented not as add-ons but as core biological traits.

Clinically, this chapter reinforces pattern recognition: ventilator-associated pneumonia, burn wound infection, catheter-associated bacteraemia, and difficult-to-treat chronic lung disease.

Conceptually, Pseudomonas represents opportunism amplified by adaptability.

Key Takeaways

* Pseudomonas aeruginosa is a non-fermenting Gram-negative rod

* It thrives in moist environments and hospital settings

* Biofilm formation enables chronic and device-associated infection

* Intrinsic and acquired resistance complicate therapy

* Disease primarily affects vulnerable hosts

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