[Community-acquired pneumonia: pathogens and course in patients admitted to a general hospital]

To determine prognostic factors and the significance of (non-invasive) microbiological tests for the clinical course of patients admitted to one general hospital with community-acquired pneumonia (CAP).

Prospective observational study.

Patients admitted to one location of a general hospital with symptoms of CAP during the period January 1998-December 1999 were included. Data from the anamnesis, physical examination and laboratory tests were recorded and samples were taken for diagnosis of the possible pathogens. Cultures were made of sputum and blood, serum and sputum were examined for infection with viral and atypical microorganisms, and the urine was screened for Streptococcus pneumoniae and Legionella antigens.

Of the 157 patients studied, 28 (18%) died as a direct result of CAP. In a stepwise multivariate analysis, age > or = 65 years, increased serum-creatinine levels and hypercapnia were independent predictors of mortality. Streptococcus pneumoniae and Haemophilus influenzae were detected 53 and 19 times, respectively, and were the bacterial pathogens most frequently found. Among the nonbacterial pathogens, Mycoplasma pneumoniae was found 37 times and serologic tests for influenza A or B virus were positive in 34 cases. In 62 patients (39%), extensive microbiological tests revealed signs of a combined infection and in 20 patients (13%) no microorganism could be detected. An elevated serum-procalcitonin level was associated with bacterial infections. As a consequence of their retrospective nature, the results of the extensive serological tests did not contribute to reaching a diagnosis in daily clinical practice. In comparison with the literature, there was a markedly high number of subclinical or atypical infections with Legionella (8%) and Bordetella (18%) and a high incidence of viral and atypical microorganisms as the cause of CAP.