Scanning electron micrograph (SEM) of anthrax cells in spleen. Anthrax bacteria (Bacillus anthracis) are rod-shaped,Gram-positive bacteria which are highly pathogenic. Commonly an infection of livestock, B. anthracis is transmitted to humans by contact with contaminated animal hair, hides or excrement. Two forms of the disease occur: pneumonia in the lungs (woolsorter's disease), and cutaneous anthrax, which causes a large boil at the sit of the bactera's entry. Antibiotic treatment, if prompt, may be effetive for the skin infection. Pulmonary anthrax is fatal in most cases. Enhanced DOD photo.