Identification of Legionella pneumophila antigens and antibodies by immunoferritin electron microscopy.

Material from 18 lungs positive for Legionella pneumophila and 21 strains of legionella grown on bacteriological media or in the yolk sac of fertile hen's eggs were examined by direct negative stain and immunoferritin electronmicroscopy. The 18 lung samples and all preparations of cultivated organisms showed the presence of bacteria with the typical morphology of L. pneumophila. By immunoferritin electronmicroscopy, with specific antisera, it was possible to serogroup the organisms. The immunoferritin method in reverse made it possible to detect and titrate antibody in sera from patients. Direct and immunoferritin electronmicroscopy were as sensitive as immunofluorescent antibody tests for detecting the antigens and antibodies of Legionnaires' disease. Additional advantages of the ultrastructural technique are discussed.