Legionella is a type of bacterium found naturally in freshwater environments, like lakes and streams. It can become a health concern when it grows and spreads in human-made water systems such as building premise plumbing and cooling towers (structures that contain water and a fan as part of centralized air-cooling systems for building or industrial processes). Legionella can continue to persist in the water system unless proper steps are taken to prevent the growth of bacteria.
Outbreaks of Legionnaires’ disease are often associated with large or complex potable water systems.
Urine antigen testing via immunochromatography is a widely available, quick diagnostic test with a > 85% sensitivity and > 99% specificity for Legionella pneumophila. However, the available assay only tests for L pneumophila serogroup 1
Antimicrobial therapy is dictated by the severity of the infection, underlying conditions or allergies, antimicrobial resistance, and medication availability. Some guidelines and studies suggest that macrolides may be superior to fluoroquinolones. Parenteral therapy is the preferred initial treatment modality; patients should be transitioned to oral therapies with clinical improvement.