Bacillus anthracis

Background

Microbiology

• Gram-positive bacillus that is distinguished from other Bacillus species by being non-motile and non-hemolytic
• Colonies are gray, flat, and may have a "Medusa head" or "comet" appearance
• The main toxin has subunits A and B
  • A subunit may be either EF (edema factor) or LF (lethal factor)
  • B subunit is the protective antigen, against which antibodies react
• Lives in soil
• Wild and farm animals that have contact with contaminated soil is a common exposure, including to wool and animal hides
• Can also be acquired by inhalation of spores

Clinical Manifestations

Cutaneous Anthrax

• Caused by inoculation of spores into soft tissue
• Incubation period of 2 to 5 days
• Lesion develops at site of inoculation, starting as erythemaous papule, then ulceration, then eschar
• May progress to sepsis

Pulmonary Anthrax

• Caused by inhalation of spores
• Also known as woolsorter's disease
• Start with malaise, fever, and nonproductive cough, followed by respiratory distress, severe pulmonary edema, and death

Gastrointestinal Anthrax

• Caused by ingestion of spores
• Infects oropharynx or abdomen
• Causes sepsis