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Legionella Antigen Serogroup 1 Only — SCE Infectious Diseases MCQ

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HardRespiratory InfectionLegionella Antigen Serogroup 1 OnlySCE Infectious Diseases

An immunosuppressed patient has severe hospital-acquired pneumonia with a negative Legionella urinary antigen. Which statement most accurately guides further testing?

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Correct answer: B — Send lower-respiratory PCR and culture to detect non-serogroup-1 Legionella

Urinary antigen testing is valuable but predominantly detects L. pneumophila serogroup 1. It can miss non-serogroup-1 strains and other species, a particular concern in healthcare-associated and immunocompromised patients. Lower-respiratory PCR and culture broaden detection, and culture also enables reference typing and source comparison.

Reference: UKHSA: Legionellosis in residents of England and Wales 2024: https://www.gov.uk/government/statistics/legionellosis-in-residents-of-england-and-wales-2024/legionellosis-in-residents-of-england-and-wales-2024