Blood cultures were done in each patient before therapy was started. Invasive techniques such as bronchoscopy with broncho-alveolar washing were performed only in those patients with severe respiratory failure or with poor evolution. Serum samples, obtained in the acute stage of illness and four weeks later, were tested for antibodies to Mycoplasma pneumonia (enzyme-linked immunoab-sorbent assay), L pneumophila (indirect immunofluorescence), Cox-iella bumeti (indirect immunofluorescence) and Chlamydia psittaci (enzyme-linked immunoabsorbent assay).
Respiratory failure was considered when blood gas value levels showed hypoxemia with a partial pressure of oxygen value of less than 60 mm Hg without oxygen administration.
Legionnaires* disease was diagnosed in all patients who fullfilled currently accepted criteria: (1) isolation of the microorganism in respiratory specimens, (2) a fourfold or greater rise in specific antibody titer, or (3) a single titer of at least 1/256. Only in 24 of 30 patients with Legionnaires’ disease were serum samples obtained in the acute and convalescent stages of the disease. The remaining six patients (three who died and three who did not achieve control of the disease) were diagnosed by culture (five cases) and by a single titer of 1/256 (one case).