Comparative Study of Pneumonia Caused by Streptococcus pneumonia and Legionella pneumophila

Abstract

Background: Legionella pneumophila has been recognized as an important cause of pneumonia. However, limited data are available in the literature regarding legionella pneumonia in Korea. The objective of this study was to compare epidemiological data and clinical presentation of legionella pneumonia and pneumococcal pneumonia. Methods: We retrospectively compared clinical, radiological, and laboratory data, antimicrobial treatment, and treatment outcomes between 28 cases of legionella pneumonia and 56 cases of pneumococcal pneumonia. Diagnoses of both legionella and pneumococcal pneumonia were based on commercial urinary antigen tests. Results: Legionella pneumonia patients included 23 men and 5 women, with a mean age of 61.6 years (range 36∼88). Fifteen were smokers and 26 had some underlying diseases. Legionella pneumonia occurred more frequently in healthcare-associated settings than pneumococcal pneumonia (42.9% vs 21.4%, respectively, p=0.040). There were no significant differences in clinical signs and symptoms. Compared to patients with pneumococcal pneumonia, patients with legionella pneumonia presented more frequently with anemia (39.3% vs 8.9%, p=0.001), increased C-reactive protein (57.1% vs 30.4%, p=0.018) and increased alkaline phosphatase (46.4% vs 16.1%, p=0.003). Also, legionella pneumonia patients more often showed pleural effusion on simple chest X-rays (50.0% vs 12.5%, p＜0.001). Conclusion: Legionella pneumonia and pneumococcal pneumonia can not be distinguished by clinical manifestations alone. However, legionella pneumonia occurred as a healthcare-associated pneumonia more frequently and was more often associated with anemia and increased CRP and alkaline phosphatase levels.