Clinical, laboratory, and imaging data were recorded for each patient including: i) clinical presentation; ii) body temperature, iii) arterial blood gas, iv) peripheral blood cell counts, v) gram stains and cultures of all biological fluids obtained (blood, sputum, bronchial secretions, BAL, and pleural fluid); vi) imaging findings, vii) antigen serology (Legionella spp and Streptococcus pneumonia urinary antigen, serological testing for Legionella pneumophila, Mycoplasma pneumoniae, Chlamydia pneumoniae) and viii) in-hospital mortality. The severity of illness was assessed by calculating Acute Physiology and Chronic Health Evaluation (APACHE) II, Sequential Organ Failure Assessment (SOFA) and Clinical Pulmonary Infection (CPIS) scores at admission [23] .