Case 69. Legionella pneumonia (neonate M)
         
   
Fatal hospital-acquired pneumonia seen in a premature infant
   
         
   
Key words : Legionella pneumophila, hospital-acquired infection
   
     
 
     
The lung is massively infiltrated by macrophages (HE). This nosocomial infection was transmitted through moist air supplied to the couveuse.   Numerous short rods are seen in the cytoplasm of alveolar macrophages (Warthin-Starry's silver).
     
 
     
Relationship between Legionella pneumophila and free-living ameba in warm water
The free-living ameba likes 42℃ (hot spring water), and L. pneumophila requires the ameba for replication. L. pneumophila belongs to the obligate intracellular bacteria, so that ameba or macrophages are definitely needed for them to grow. Hot spring bathing is a risk factor of Legionella pneumonia in the aged.
  Reference case 69A
Open lung biopsy specimen of legionnaire's disease in a 65 y-o male. The bacteria are mainly phagocytized by self-replicable macrophages and not by short-lived neutrophils.