Pneumonia caused by Legionella pneumophila serogroup 6 after drowning in a home bathtub: A case report.

Legionella pneumophila infections are typically caused by exposure to contaminated water. Herein, we report a case of L. pneumophila pneumonia that likely resulted from the aspiration of contaminated bathwater after the patient drowned in a bathtub at home, rather than from exposure in a public bathhouse or circulating system. A 71-year-old man was brought to our hospital after drowning in a bathtub (day 1). The patient presented with severe respiratory failure and impaired consciousness. Chest radiography revealed extensive infiltrative opacities in the lung fields, and a rapid diagnostic test revealed positivity for influenza antigens. Aspiration and influenza pneumonia were initially suspected, and systemic management including intensive care was consequently initiated. Despite this treatment, the patient's clinical course remained poor. On Day 7 of illness, the patient's urinary antigen test was positive for Legionella, leading to a diagnosis of Legionella pneumonia. Legionella pneumoniae can be caused by aspiration after drowning. Diagnostic difficulties due to nonspecific clinical presentation and poor general condition after drowning should be considered. In cases of drowning that do not respond to standard treatments, L. pneumophila infection should be considered in the differential diagnosis.