Fatal Legionella pneumonia: retrospective examination of lung tissue using direct and indirect fluorescent-antibody methods.

Lung tissue sections of patients who died of pneumonia within one year were screened retrospectively for Legionnaires' disease bacteria using simultaneously a direct fluorescent antibody test (DFA) and an indirect fluorescent antibody system (IFA). The IFA has shown to provide a rapid screen for the increasing number of known Legionella species and serogroups recently. In 10/168 (6%) of our cases legionellae were the pneumonia causing agents detected with both methods. Although we should have been able to detect 25 serological variants of Legionella species and serogroups with the IFA, we found Legionella pneumophila serogroup 1 only. The IFA test has proven to be a reliable means for the screening of lung tissue sections.