Anthrax antibiotics research. Discs impregnated with antibiotic drugs being tested against Bacillus anthracis bacteria (silver). The bacteria have been cultured (grown) on nutrient agar. The exclusion zones around each disc demonstrate the effectiveness of that antibiotic. B. anthracis is the cause of anthrax. It can infect the skin (cutaneous anthrax), causing raised itchy lesions, the lungs (pulmonary anthrax), which is fatal unless treated quickly, and the digestive system (gastrointestinal anthrax), causing vomiting of blood and severe diarrhoea. All forms can be fatal if left untreated.