Abstract: Objective  To summarize the clinical characteristics and outcomes associated with Legionella pneumophila pneumonia, thereby enhancing clinicians' understanding of this disease. Methods  A retrospective analysis of the clinical characteristics and prognostic outcomes of patients diagnosed with Legionella pneumophila pneumonia at The First Hospital of Changsha from October 2021 to July 2024. Results  The study included 50 male and 21 female participants, with an average age of (62.6±15.9) years. Common symptoms included cough (n =58), expectoration (n= 51), Dyspnea (n=34), fever (n=33), headache (n =13), fatigue (n= 9), and myalgia (n=8). Dyspnea was the only clinical symptom that showed a significant difference between the severe and non-severe pneumonia groups. The levels of procalcitonin (PCT), C-reactive protein (CRP), D-dimer, creatine kinase (CK), and CK-myocardial band (CK-MB) were significantly higher in the severe pneumonia group compared to the non-severe group. Conversely, lymphocyte count, platelet (PLT) count, and albumin levels were significantly lower in the severe group (P<0.05). Common computed tomography (CT) manifestations included flake-like high-density shadows (n = 62, 87.3%), small pulmonary nodules (n = 23, 32.4%), pleural effusion (n=18, 25.4%). Common complications included electrolyte disorders (n=26), type I respiratory failure (n=22), acute liver injury (n=20), sepsis (n=13), acute renal impairment (n=11), septic shock (n=6), multiple organ dysfunction syndrome (MODS) (n=4), and acute respiratory distress syndrome (ARDS) (n=2). The rate of intensive care unit (ICU) admission was 22.5% and the overall mortality rate during hospital was 4.2%(n=3). The majority of patients received treatment with quinolones (59 out of 71, 83.1%). Specifically, 38 patients were treated exclusively with quinolones, while 3 patients received azithromycin alone. A total of 7 patients received invasive ventilation treatment, while 11 patients were treated with non-invasive ventilation. Unfortunately, 3 patients in the severe pneumonia group died due to sepsis and multiple organ failure. Conclusion  If Legionella pneumophila infections are not diagnosed promptly, patients may experience severe pneumonia, multiple organ failure, or even fatal outcomes. The early initiation of quinolones or combination therapy with other medications has shown significant therapeutic benefits for patients suffering from Legionella pneumophila pneumonia.

Key words: Legionella pneumophila, pneumonia, clinical characteristics, treatment strategies, quinolone, azithromycin.