Legionella pneumophila was first isolated in 1976 and is now recognized to be a common cause of community-acquired and nosocomial pneumonia. Legionella pneumophila serogroup 1 causes the majority (80-85%) of cases of Legionnaires Disease. The disease presents with broad spectrum symptoms, from a mild cough, fever and gastrointestinal involvement to complete respiratory and multiorgan failure. Disease can be acquired by the inhalation of aerosols associated with air handling systems, respiratory therapy equipment, and whirlpool baths. The most susceptible patient groups include the elderly, children and neonates. Rapid diagnosis and early initiation of appropriate antimicrobial therapy can significantly reduce the mortality associated with Legionella pneumonia (up to 25% in untreated immunocompetent patients).


With the limitations of traditional specimen types (sputum, bronchial washing, transtracheal aspirate, lung biopsy and serum), urine being non-invasive is now preferred. The soluble Legionella antigen (LUA) excreted in approximately 80% of Legionella pneumonia patients presented an identifiable antigen for easy and rapid detection of Legionella in urine. Both ELISA and ICT have been adapted for effective detection of the LUA in patients with Legionella pneumophila serogroup 1 infection. Diagnosis is confirmed using culture methods.

Monitoring therapy effectiveness (serum) and specie/subgroup identification (respiratory sample) may be done using antibody ELISA or IFA/DFA respectively.