Legionella

Question 1

What is the cause of Legionnaire’s Disease?

Answer 1

Legionella pneumophilia (an intracellular bacterium)

Question 2

Where is it typically found?

Answer 2

In water tanks.

So questions will usually hint at air-conditioning systems or foreign holidays.

Question 3

What are some features of legionnaire’s disease?

Answer 3

• Flu-like symptoms including fever (present in > 95% of patients)
• Dry cough
• Relative bradycardia
• Confusion
• Lymphopaenia
• Hyponatraemia
• Deranged liver function tests
• Pleural effusion: seen in around 30% of patients

Question 4

How do you diagnose legionnaire’s disease?

Answer 4

Urinary antigen

Question 5

What is the treatment for legionnaire’s disease?

Answer 5

Erythromycin

Question 6

Answer 6

Chest x-ray features of legionella pnuemonia are non-specific but includes a mid-to-lower zone predominance of patchy consolidation. Pleural effusions are seen in around 30%.