[Etiology of community-acquired pneumonia in ambulatory patients. Usefulness of a diagnostic investigation protocol using detection of Streptococcus pneumoniae and Legionella pneumophila antigens in urine samples]

Abstract

Background: To determine the etiology of community-acquired pneumonia (CAP) in ambulatory patients and to assess the efficiency of a diagnostic protocol by using tests to detect bacterial antigens in urine samples.

Patients and method: One-year prospective study that included blood and sputum cultures, serologic studies, and detection of Legionella pneumophila and Streptococcus pneumoniae urinary antigens.

Results: 49 patients were recruited and an etiological diagnosis was attained in 34 (69%). Microorganisms most frequently isolated were S. pneumoniae (12 cases), Mycoplasma pneumoniae (7), Haemophilus influenzae (4), respiratory viruses (4) and Coxiella burnetii (3 cases).

Conclusions: By means of a non-invasive protocol with urinary antigen tests, a microbial etiology can be established in two thirds of patients with mild CAP. S. pneumoniae is the main cause of mild CAP.