The hypothesis is that community-acquired pneumonia is usually a monomicrobial infection. Therefore, early detection of the etiology allows to select the most active, narrow-spectrum, and cheap, and less toxic antibiotic agent.

In community-acquired pneumonia, identification of the etiologic agent has theoretically important advantages. For individual patients, it facilitates the administration of a targeted, narrow-spectrum antibiotic therapy that may improve the efficacy of treatment, and reduces risks of antibiotic-related toxicity. For the community, microbiologic results contribute to understanding the local microbial epidemiology of community-acquired pneumonia and the antimicrobial resistance patterns of pathogens, information that is essential in the instauration or modification of empiric treatment regimens.

Guidelines recommend that all admitted patients with community-acquired pneumonia should have a collection of two sets of blood cultures, a good quality sputum sample for Gram stain and culture, a sample of pleural fuid if present and, for severe patients, an urine sample for antigen detection. In contrast, several prospective studies (usually without include urinary tests) concluded that these microbiological studies have limited value in the management of patients admitted with community-acquired pneumonia.

In addition, microbiological studies could provide erroneous or incomplete information. Thus, investigations has showed false-positive results from pneumococcal antigen detection in urine caused by a frequent persistence of positivity after infection or a nasopharyngeal or bronchial colonization. Other authors suggested that community-acquired pneumonia is a polymicrobial infection; consequently, despite the detection of a true microorganism, treatment needs to be also addressed against other potential pathogenic agents.

The purpose of the study is to assess the clinical and the economic derived from the initial microbiological studies, including antigen detection tests in urine for Streptococcus pneumoniae and Legionella pneumophila, in patients with community-acquired pneumonia.

The hypothesis is that community-acquired pneumonia is usually a monomicrobial infection. Therefore, early detection of the etiology allows to select the most active, narrow-spectrum, and cheap, and less toxic antibiotic agent.

Inclusion Criteria:

• Age: 18 years and above
• Clinical and radiological diagnosis of community-acquired pneumonia
• Informed consent of patient
• Hospital admission

Exclusion Criteria:

• Prior hospital admission (less than 15 days)
• Alternative diagnosis at the discharge
• Immunosuppression (HIV infection, immunosuppressive therapies, neutropenia)
• Risk factors for unusual etiologies
• Patient is pregnant