A Case of Legionella Pneumonia in an Older Patient Without Typical Exposure to a Susceptive Environment

Legionella pneumonia is a potentially fatal form of pneumonia that causes various clinical symptoms and is often difficult to diagnose. For the diagnosis, it is important to inquire about the patient's history of exposure to sewage or soil, although there are rare cases of Legionella pneumonia with no history of exposure. In this study, we present a case of Legionella pneumonia in a 72-year-old man with no history of wastewater exposure from public baths or other sources. The patient presented to our emergency department with fever, chills, and shivering. The antigen test of the urine for Legionella was negative, and chest radiography showed patchy infiltrates in the right lower lung field that was suspicious for pneumonia. The patient was treated with intravenous ceftriaxone (2 g/day) for right-sided pneumonia and was intubated on day 1 due to poor oxygenation and a tendency towards exacerbation to acute respiratory distress syndrome. The fever resolved after day 3 (36.4-36.9°C), and the patient was extubated on day 6. A positive sputum polymerase chain reaction (PCR) test for Legionella deoxyribonucleic acid (DNA) (type 1) was performed on day 6, and levofloxacin and dexamethasone therapy was administered. After completing a 10-day course of levofloxacin, the patient's symptoms were cured. Although it is important to note the patient’s background, symptoms, and information on the clinical course, including laboratory values, to include a diagnosis of Legionella pneumonia, it is impractical to suspect Legionella pneumonia in all patients admitted to the hospital with pneumonia and to administer new quinolone antimicrobials. However, it is important to re-evaluate the diagnosis and intervene in treatment when β-lactam antimicrobials are ineffective or when extrapulmonary symptoms are present, as in this case.