[Detection of legionellas in clinical samples using FITC-marked antibodies]

Using serogroup/species specific FITC-conjugates against Legionella (L.) pneumophila serogroups (SG) 1 to 6, L. micdadei, L. bozemanii and L. jordanis 186 sputum samples, 43 pleural fluids and bronchial washings and 39 lung tissue samples from 251 pneumonia patients were checked for Legionellae with the direct fluorescent antibody technique (DFAT). In samples from 201 patients which were negative if tested for antibodies and for urinary antigen and/or using culture methods, the DFAT was negative, too. One Pseudomonas strain isolated from a bronchial washing showed crossreactions. In 19 out of 49 patients with legionellosis L. pneumophila SG 1 (3x), SG 2 (1x), SG 3 (4x), SG 4 (1x), SG 5 (5x), L. micdadei (3x) and L. bozemanii (2x) were found. Positivity of the DFAT was significant higher in specimens, taken in early stages of illness (p less than 0.01). DFAT can be used for specific detection of Legionellae in clinical specimens, but the relative low sensitivity (39%) does not allow to exclude legionellosis. Further diagnostic tests like detection of antibodies and urinary antigen and culture are necessary to diagnose legionellosis.