Aetiology and risk factors of community‐acquired pneumonia in hospitalized patients in N orway

Background and Aims In N orway, data on the aetiology of community‐acquired pneumonia ( CAP ) in hospitalized patients are limited. The aims of this study were to investigate the bacterial aetiology of CAP in hospitalized patients in N orway, risk factors for CAP and possible differences in risk factors between patients with L egionnaire's disease and pneumonia because of other causes. Methods Adult patients with radiologically confirmed CAP admitted to hospital were eligible for the study. Routine aerobic and L egionella culture of sputum, blood culture, urinary antigen test for L egionella pneumophila and S treptococcus pneumoniae , polymerase chain reaction detection of C hlamydophila pneumoniae , M ycoplasma pneumoniae and B ordetella pertussis from throat specimens, and serology for L . pneumophila serogroup 1–6 were performed. A questionnaire, which included demographic and clinical data, risk factors and treatment, was completed. Results We included 374 patients through a 20‐month study period in 2007–2008. The aetiological agent was detected in 37% of cases. S . pneumoniae (20%) was the most prevalent agent, followed by H aemophilus influenzae (6%) and L egionella spp. (6%). Eight L egionella cases were diagnosed by urinary antigen test, of which four also had positive serology. In addition, 13 L egionella cases were diagnosed by serology. The degree of comorbidity was high. An increased risk of hospital‐diagnosed L egionella pneumonia was found among patients with a diagnosis of chronic congestive heart failure. Conclusion Our results indicate that S . pneumoniae is the most common bacterial cause of pneumonia in hospitalized patients, and the prevalence of L egionella pneumonia is probably higher in N orway than recognized previously.