++
For further information, see CMDT Part 35-15: Legionnaires Disease
++
An important cause of community-acquired pneumonia
Classically, Legionnaires disease is caused by Legionella pneumophila, though other Legionella species can cause identical disease
Occurs more commonly in immunocompromised persons, in smokers, and in those with chronic lung disease
Outbreaks have been associated with contaminated water sources, such as shower heads and faucets in patient rooms and air conditioning cooling towers
++
Many features of typical pneumonia, with high fevers, a toxic appearance, pleurisy, and grossly purulent sputum
Nausea, vomiting and diarrhea may be prominent
There may be relative bradycardia
++
There may be hyponatremia, hypophosphatemia, elevated liver enzymes, and elevated creatine kinase
Testing sputum samples using polymerase chain reaction is a highly sensitive method for diagnosing Legionella
Culture of Legionella species has up to 80% sensitivity
Culture onto charcoal-yeast extract agar or similar enriched medium
Dieterle silver staining of tissue, pleural fluid, or other infected material is also a reliable method for detecting Legionella species
Direct fluorescent antibody sputum stains may also be performed
Legionella serology and urinary antigen are less sensitive diagnostic methods; the latter will detect only L pneumophila serotype 1
++