Cureus. 2025 Oct 31;17(10):e95860. doi: 10.7759/cureus.95860. eCollection 2025 Oct.

A 66-year-old man with no relevant medical history developed pneumonia. Urine antigen tests for pneumococcus and Legionella serotype 1 (the most common serotype) were negative, but sputum culture was positive for methicillin-susceptible Staphylococcus aureus (MSSA) and β-lactamase-negative Haemophilus influenzae (BLNAR). The patient was treated with meropenem and azithromycin, but an aerobic blood culture became positive on day 4, and mass spectrometry analysis indicated the presence of Legionella species. Subculture on buNrNL charcoal yeast extract (BCYE)-α agar identified Legionella pneumophila serotype 3. The patient was diagnosed with pneumonia caused by MSSA and BLNAR, as well as pneumonia/bacteremia due to Legionella pneumophila serotype 3. Despite changing the antibiotics to meropenem plus lascufloxacin and adding hydrocortisone and venovenous extracorporeal membrane oxygenation (V-V ECMO), the patient died. In patients with severe pneumonia, co-infection with Legionella species, including rare serotypes, should be considered, and universal rapid antigen tests are necessary to ensure rapid diagnosis and appropriate treatment.

PubMed:41333955 | PMC:PMC12665617 | DOI:10.7759/cureus.95860