Detection of acute infection due to Legionella pneumophila in patients with community-acquired pneumonia in Buenos Aires city

Community-acquired pneumonia (CAP) is caused by different microorganisms, their frequency varying in each community. Legionella pneumophila has been reported as etiologic agent of CAP. The aim of our study was to determine the incidence of acute infection due to Legionella pneumophila in a group of adult patients in Buenos Aires city. Adults of both sexes with CAP diagnosis were included and two serum samples, acute and convalescence (2-4 weeks apart from each other), were tested to detect antibodies against Legionella pneumophila by indirect immunofluorescence (IFI) (Organon Teknica, NC, USA). Ninety-two of the enrolled patients were evaluable, average age 56 years, 55% men (males), 52.2% did not require hospitalization. Three patients (3.3%) fulfilled the serologic diagnostic criteria for Legionella pneumophila acute infection. None of them were confirmed by microorganism isolation. The actual incidence of CAP caused by Legionella pneumophila in Argentina has not yet been established. It will require studies including larger numbers of patients and the use of simple and sensitive tests, such as Legionella pneumophila urinary antigen detection, to establish the exact role of this pathogen in our community.