Gram negative bacilli
Reservoir is water. Aerosolization by cooling towers, spas, shower heads, etc.
Occurs in outbreaks.
Person-to-person transmission not documented.
Legionella pneumophila is a rare cause of community-acquired pneumonia but can be associated with significant morbidity and mortality if unrecognized or improperly treated. Risk factors include immunocompromised patient, smoking, co-morbidities.
Given that Legionella pneumophila is difficult to detect in culture, a Legionella urinary antigen or PCR testing can assist in diagnosis.