MRCP revision battle 17.4: Legionella

Legionella is a gram negative bacteria which causes legionella disease/pneumonia and in MRCP questions is most likely found living in a cruise ship/hotel's water tank or airconditioning system.



The symptoms of legionella disease are:

• flu-like
• dry cough
• dypnoea
• GI upset

Complications of legionella which may show up in the blood results include:

• SIADH - low sodium
• hepatitis - deranged LFTs

Legionella is killed above 60c, cannot multiply between 50 and 60c and are happiest between roughly 35 to 45 c


Males are more affected than females, 3:1


CXR may show bibasal consolidation.


Treatment is with antibiotics which achieve a high intracellular concentration, such as clarithromycin, rifampicin or fluroquinolone.


Legionella has a 10% mortality.



Lets now trot on to pleural calcification...