Superficial exudates of neutrophils prevent invasion of Bacillus anthracis bacilli into abraded skin of resistant mice.

Skin window procedures in humans have shown rapid accumulation of neutrophils into the exuded fluids above abraded skin. The present study was undertaken to determine if similar epicutaneous neutrophil accumulation might explain the extreme resistance of HRS/J mice, both hairless (hr/hr) and haired (hr/+), to experimental cutaneous Bacillus anthracis Sterne infections on abraded skin. In this study, very early (6 h) biopsies demonstrated a lack of bacilli in skin from the HRS/J hr/hr mice, indicating that the organisms never did invade in these animals as opposed to early skin entry and then efficient clearance by host responses in the tissues.

Characteristics of spore germination in a mouse model of cutaneous anthrax.

Background: Cutaneous infection is the most common form of human anthrax, but little is known about Bacillus anthracis spore germination in these infections.

Methods: We used experimental inoculations of B. anthracis Sterne spores or vegetative bacilli onto intact or abraded mouse flank skin, followed by evaluation of the infections and enumeration of germinating spores and vegetative bacilli.

Experimental cutaneous Bacillus anthracis infections in hairless HRS/J mice.

Previous studies of experimental Bacillus anthracis cutaneous infections in mice have implicated hair follicles as a likely entry site. Hairless HRS/J mice were used to investigate this possibility because of their non-functional hair follicles that lack penetrating hair shafts. These mice also have diminished macrophage function, increased susceptibility to Listeria, and enhanced neutrophil responses.