2.4. Sample and clinical data collection

Respiratory samples included sputum or nasopharyngeal swab collected at inpatient admission or at the outpatient setting at the time patients were diagnosed of asthma attacks. Clinical data were also obtained at the same time. Respiratory samples for PCR-based detection of respiratory viruses, M. pneumoniae, and Chlamydophila pneumoniae were collected separately from those intended for bacterial cultures and were stored at -80°C until use. Gram stain was performed on a purulent portion of each sputum specimen and examined by trained personnel. Sputum samples were considered as good quality for evaluation if they were classified as Geckler 4 or 5. Positive bacterial culture was based on acceptable sputum samples with predominant species and compatible results from Gram staining.