Detection of Legionella pneumophila serogroup 1 in blood cultures from a patient treated with tumor necrosis factor-alpha inhibitor

A 65-year-old man was admitted to our hospital with a temperature of 39.3 °C, cough, sputum, and pharyngeal discomfort that had persisted for 3 days. He had been treated with methotrexate and adalimumab (a tumor necrosis factor-alpha [TNF-α] inhibitor) for rheumatoid arthritis for 2 years, and he had also been treated with S-1 (tegafur, gimeracil, and oteracil potassium) for pancreatic metastasis of gastric cancer for 2 months. Regardless of the underlying pathologies, his general condition was good and he had worked as an electrician until 2 days before admission. However, his appetite had suddenly decreased from the day before admission, and high fever and hypoxia were also evident upon admission. A chest X-ray and computed tomography scan revealed left pleural effusion and consolidation in both lungs. The pneumonia severity index score was 165 and the risk class was V. Accordingly, we started to treat the pneumonia with a combination of levofloxacin and meropenem. Thereafter, we received positive urinary antigen test findings for Legionella pneumophila. After hospitalization, hypoxia was progressed and hypotension was emerged. Despite the application of appropriate antibiotics, vasopressors, and oxygenation, the patient died 8 h after admission. Even after his death, blood cultures were continued to consider the possibility of bacterial co-infection. Although no bacteria were detected from blood cultures, Gimenez staining revealed pink bacteria in blood culture fluids. Subsequent blood fluid culture in selective medium revealed L. pneumophila serogroup 1. Recently, TNF-α inhibitors have been described as a risk factor for Legionnaires’ disease. In consideration of the increased frequency of TNF-α inhibitors, we may need to recognize anew that L. pneumophila might be a pathogen of severe community-acquired pneumonia.