FIG. 3.

Time course of infection, as detected by microscopic examination of peritoneal lavage fluids. Cytospin preparations were prepared from peritoneal lavage fluid samples collected from saline-pretreated mice retaining native macrophage populations (S) and mice that had been depleted of macrophages by administration of clodronate liposomes (C). Samples were examined at 1 h, 3 h, 5 h, 7 h, and 9 h after i.p. challenge with approximately 1.8 × 10⁷ B. anthracis Ames strain spores. The 1-h samples were concentrated approximately fourfold before being mounted on the slide to visualize spores (arrows). In both the S 1-h and the C 1-h samples, ungerminated and germinated spores were observed, as determined by malachite green/Diff-Quik staining. The magnification was ×60, except for the 1-h samples, which were observed at ×100 to visualize spores.