Pseudomonas aeruginosa

It is sometimes said that those who know pseudomonas know bacteriology. There is an element of truth in this. It is a fascinating pathogen with many defence and attack determinants. This tutorial does not attempt to teach comprehensively the bacteriology of Pseudomonas. For this you should refer to the section on Pseudomonas aeruginosa in Todar’s textbook on bacteriology. It is an excellent summary of the bacteriology of Pseudomonas.

Rather I want to share with you specific points (mostly clinical) I have learnt about Pseudomonas aeruginosa while working in the laboratory:


1)      It is usually an opportunistic pathogen but otitis externa and spa pool folliculitis are examples of it causing infection in healthy tissue.

2)      Pseudomonas aeruginosa can infect almost any organ system.

3)      When Pseudomonas aeruginosa causes a UTI it is usually associated with an indwelling catheter

4)      When pseudomonas is found in a sputum sample, it usually indicates architectural lung disease, e.g. CF, bronchiectasis, severe COPD. When it is found in the sputum of a child, it should prompt further investigation for CF/bronchiectasis.

5)      Pseudomonas aeruginosa carries one of the highest, if not the highest mortality of all organisms when it causes bacteraemia, approximately 35% mortality at 30 days.

6)      Pseudomonas aeruginosa can be very resistant, and in particular in CF patients where it often is found in the mucoid form, minimising antibiotic penetration.

7)      Pseudomonas aeruginosa sometimes colonises chronic ulcers. In this clinical setting it only rarely causes infection. Even when it does, anti-septic dressings may be as effective as systemic antimicrobials in this setting.



Here are some MCQs on the basic bacteriology of Pseudomonas aeruginosa.



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