Microbiology · Gram-positive rods
Bacillus anthracis !
- Bacterium
- Gram-positive
- For completeness
A spore-forming bacterium of soil and livestock that causes skin, lung or gut anthrax; it does not spread between people.
Updated 2026-11-01
Also called: anthrax
At a glance
- Gram
- Gram-positive
- Shape
- Large rods in chains (bamboo cane)
- Oxygen
- Aerobe or facultative anaerobe
- Family
- Bacillaceae
- Stain
- Gram positive; spore former
Morphology
- Large Gram-positive rods in chains
- Protein capsule (poly-D-glutamic acid), a rare exception to the usual polysaccharide capsule
- Medusa-head colonies; non-motile
Transmission
- Contact with infected animals or animal products (hides, wool)
- Inhaling spores
- Eating contaminated meat
- Not spread from person to person
Isolation precautions
What the care team adds to standard precautions.
- Standard
Virulence factors
- Poly-D-glutamic acid capsule: antiphagocytic
- Edema toxin (edema factor + protective antigen): adenylate cyclase
- Lethal toxin (lethal factor + protective antigen): a protease that wrecks signalling pathways
Diseases it causes
- Cutaneous, inhalation, gastrointestinal and injection anthrax Anthrax →
Clinical picture
- A papule that becomes an ulcer with a painless black eschar and oedema
- Inhalation: flu-like illness that progresses to shock with mediastinal widening
- Haemorrhagic meningitis in disseminated disease
Diagnosis
- Gram stain and culture of the lesion, blood or pleural fluid
- X-ray or CT: widened mediastinum and pleural effusion
- PCR and lethal factor detection in reference labs
Treatment
Antibiotics such as ciprofloxacin or doxycycline for treatment and post-exposure prophylaxis; systemic disease combines several antibiotics with antitoxins (monoclonal antibodies) and intensive support.
Drug class only; doses and regimens are set by the clinician from the current guideline.
In Pharmacology:
Prevention
- Vaccinating livestock where cases have occurred
- Human vaccine for high-risk work
- Antibiotic prophylaxis and vaccine after spore exposure
Test yourself
Think of the answer, then tap the question to see it.
What is special about the B. anthracis capsule?
It is made of protein (poly-D-glutamic acid), not polysaccharide like other encapsulated bacteria.
Which imaging finding suggests inhalation anthrax?
A widened mediastinum, often with pleural effusion.
What does the cutaneous anthrax lesion look like?
An ulcer with a painless black eschar surrounded by oedema.
Related
Related conditions
← Back to the group: Gram-positive rods
Educational content on microorganisms; not a treatment guide and no substitute for a health professional's advice. No doses are given.
Sources: About Anthrax (CDC, 2024); Clinical Overview of Anthrax (CDC, 2024).
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Representative model, for educational purposes only.