Germination of Bacillus anthracis spores within alveolar macrophages

The fatal character of the infection caused by inhalation of Bacillus anthr acis spores results from a complex pathogenic cycle involving the synthesis of toxins by the bacterium. We have shown using immunofluorescent staining , confocal scanning laser microscopy and image cytometry analysis that the alveolar macrophage was the primary site of B. anthracis germination in a m urine inhalation infection model. Bacillus anthracis germinated inside muri ne macrophage-like RAW264.7 cells and murine alveolar macrophages. Germinat ion occurred in vesicles derived from the phagosomal compartment. We have a lso demonstrated that the toxin genes and their trans-activator, AtxA, were expressed within the macrophages after germination.