BACKGROUND: Despite rigorous investigations, the etiology of community-acquired pneumonia remains unknown in about 50% of hospitalized patients. The diagnosis of the etiological agent is becoming more challenging and more critical as number of newer pathogens have been recognized in recent years. In the 3-year period prospective study we investigated adult patients with community-acquired pneumonia for Legionella, Leptospira, Hantaan virus and Orientia tsutsugamushi as potential etiologic agents. METHODS: A prospective multicenter study was performed from May 1997 to April 2000. A total of 431 patients with community-acquired pneumonia under the inclusion criteria were examined for specific microbial diagnosis; sputum culture and PCR, and serologic teats including indirect immunofluorescence antibody (IFA) test for Legionella, and hemagglutination tests for Leptospira, Hantaan virus and O. tsutsugamushi. Etiologic diagnosis was determined on the basis of the review of case record forms and specific laboratory diagnostic criteria. RESULT: During the study period a total of 385 sputum and 283 serum samples were examined. Legionella pneumonia was diagnosed in 2.3% (10/431) of the cases examined: 1.4% cases with PCR-positive (5/ 367) and 2.1% with positive IFA test (6/283). Leptospirosis and scrub typhus were diagnosed in 0.4% (1/ 252) and 2.0% (5/252), respectively. All 5 cases diagnosed as scrub typhus occurred in late fall, and rash or eschar was not found. None of cases was Hantaan virus infection. CONCLUSION: The results suggest that Legionella, Leptospira, and O. tsutsugamushi should be considered in the etiologic diagnosis and in empirical antibiotic therapy of community-acquired pneumonia.
Adult* ; Diagnosis ; Exanthema ; Fluorescent Antibody Technique, Indirect ; Hantaan virus* ; Hemagglutination Tests ; Humans ; Legionella* ; Leptospira* ; Leptospirosis ; Orientia tsutsugamushi* ; Pneumonia* ; Polymerase Chain Reaction ; Prospective Studies* ; Scrub Typhus ; Sputum