Case 70. Lobar pneumonia (88 y-o M)
Fatal lobar pneumonia in the aged (four-day clinical course)
Key words : Lobar pneumonia, Legionella pneumophila
The alveolar space is massively and diffusely infiltrated by neutrophils and macrophages (HE, low power).   Both neutrophils and macrophages are seen in the exudates (HE, high power). Legionella pneumonia is strongly suspected both clinically and histologically.
Numbers of argyrophilic rods are phagocytized by macrophages (Warthin-Starry's silver). E. coli antigens were negative.   Giemsa-stained touch smear prepared at autopsy gives us valuable information. Rods are clearly seen in the cytoplasm of macrophages (Giemsa). However, culture for L. pneumophila using a BCYEα culture agar was negative in this case.
Electron micrograph of the cytoplasm of an alveolar macrophage demonstrates rods with vacuolated change.