Bacillus anthracis is a gram-positive, spore-forming rod that produces anthrax toxin (an exotoxin consisting of protective antigen, lethal factor, and edema factor). Has a polypeptide capsule (poly d-glutamate). Colonies show a halo of projections, sometimes referred to as a “medusa head” appearance.

It presents as a cutaneous anthrax and a pulmonary anthrax:

• Cutaneous: Painless papule surrounded by vesicles -> ulcer with black eschar (painless, necrotic) -> uncommonly progresses to bacteremia and death.
• Pulmonary: Inhalation of spores, most commonly from contaminated animals or animal products, although also potential bioweapons -> flu-like symptoms that rapidly progress to fever, pulmonary hemorrhage, mediastinitis (CXR may show widened mediastinum), and shock. Also called woolsorter’s disease.