A 70-year-old man was admitted to the emergency room with complaints of fever and diarrhoea for 6 days. Chest radiograph films showed high-density infiltration mainly in the right lung field. His symptoms worsened and he developed somnolence and acute respiratory distress despite treatment with latamoxef. Bronchoscopy was performed and bronchoalveolar lavage fluid was collected for rapid respiratory pathogen detection using quantitative Loop-mediated isothermal amplification assay, with a positive result for Legionella pneumophila after 4 h. Intravenous moxifloxacin (400 mg/day) was added to therapy and the patient was extubated successfully after 11 days. The colonies cultured from the bronchoalveolar lavage fluid were identified as L. pneumophila serogroup 1, which confirmed the diagnosis of L. pneumophila pneumonia. This strain was characterized as sequence type 59. After review of the published literature, we found that sequence type 59 was wildly distributed throughout the world, being isolated equivalently from environmental samples (3.05%, 57/1868) and clinical samples (1.81%, 54/2984); this was the first clinical isolate in China. Further study to investigate the relationship between its unique distribution pattern and its capacity to cause disease in humans is warranted.