[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Microbiology](https://durgical.com/en/microbiology/) › [Gram-positive rods](https://durgical.com/en/microbiology/groups/gram-positive-rods/) › Bacillus anthracis

[Microbiology](https://durgical.com/en/microbiology/) · [Gram-positive rods](https://durgical.com/en/microbiology/groups/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

## Key points

- The classic bacterium with a protein capsule (poly-D-glutamate) instead of a polysaccharide one.
- Painless black eschar (cutaneous).
- Widened mediastinum (inhalation).
- Edema toxin = adenylate cyclase; lethal toxin = metalloprotease.
- Not contagious between people.

## 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 →](https://durgical.com/en/conditions/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:

- [Ciprofloxacin](https://durgical.com/en/pharmacology/ciprofloxacin/)
- [Doxycycline](https://durgical.com/en/pharmacology/doxycycline/)

## Prevention

- Vaccinating livestock where cases have occurred
- Human vaccine for high-risk work
- Antibiotic prophylaxis and vaccine after spore exposure

## Memory aid

Anthrax comes from the Greek for coal: an eschar black as coal that, oddly, does not hurt.

## 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.

[Add to my cards (3)](https://durgical.app/estudiar/?add=/en/microbiology/bacillus-anthracis/)

## Related

- [Bacillus cereus](https://durgical.com/en/microbiology/bacillus-cereus/)
- [Clostridium tetani](https://durgical.com/en/microbiology/clostridium-tetani/)

## Related conditions

- [Anthrax](https://durgical.com/en/conditions/anthrax/)

## What the colours mean

**Gram-positive**
Thick peptidoglycan wall: stains purple.

**Gram-negative**
Thin wall with an outer membrane: stains pink.

**Acid-fast**
Lipid-rich wall (mycobacteria): Ziehl–Neelsen stain.

[← Back to the group: Gram-positive rods](https://durgical.com/en/microbiology/groups/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](https://www.cdc.gov/anthrax/about/index.html) (CDC, 2024); [Clinical Overview of Anthrax](https://www.cdc.gov/anthrax/hcp/clinical-overview/index.html) (CDC, 2024).

## **Spotted a mistake?** We are always improving for the community. Tell us what is wrong and our team will review it. Report a mistake

Representative model, for educational purposes only.

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Source: https://durgical.com/en/microbiology/bacillus-anthracis/
License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/microbiology/bacillus-anthracis/