[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].

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.