Nosocomial and Community Acquired Legionella Pneumophila Pneumonia.

Legionnaire's disease (LD) is a major cause of both community acquired and nosocomial pneumonia, with Legionella pneumophila serogroup A (Lp1) being the most virulent and the greatest cause of disease. Sample culture of low respiratory tract is considered the gold standard in the diagnosis of LD, however its sensitivity seems to be poor and its performance is technically demanding. The introduction of urinary antigen detection testing (LUA) brought a major advance in LD diagnosis, with upt to 95% of cases in Europe being diagnosed with this method. Despite the high sensitivity of LUA for Lp1, ranging from 80-90%, its negative predictive value is low in other serogroup than Lp1 and therefore, Legionella may be unrecognized as agent of pneumonia. Although underdiagnosed and underreported, LD represents the second most common cause of pneumonia requiring admission in intensive care unit (ICU). Average fatality rate of LD in Europe reaches 10%, but its mortality is considered to be even higher in nosocomial patients.

Despite the higher fatality rate in hospitalized LD patients, poor is the knowledge on the risk factors that could induce disease and that increase mortality in the hospitalized population affected by LD. In order to shed more light on this topic a cohort of patients diagnosed with LD in the last 3 years will be retrospectively examined.