[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Microbiology](https://durgical.com/en/microbiology/) › [Other Gram-negative rods](https://durgical.com/en/microbiology/groups/other-gram-negative-rods/) › Francisella tularensis

[Microbiology](https://durgical.com/en/microbiology/) · [Other Gram-negative rods](https://durgical.com/en/microbiology/groups/other-gram-negative-rods/)

# Francisella tularensis

- Bacterium
- Gram-negative
- For completeness

A bacterium of rabbits, hares and rodents spread by ticks, deer flies, contact or air; it causes tularemia and is very infectious in the lab.

Updated 2026-11-01

## Key points

- Hunter skinning a rabbit, an ulcer and large nodes: ulceroglandular tularemia.
- Ticks and deer flies as vectors.
- Needs cysteine to grow; a lab infection hazard.
- Treated with aminoglycosides (streptomycin or gentamicin).
- Facultative intracellular, like Brucella and Yersinia.

## At a glance

**Gram**
Gram-negative

**Shape**
Very small coccobacillus

**Oxygen**
Strict aerobe

**Family**
Francisellaceae

**Stain**
Gram: tiny, faintly staining red coccobacilli

## Morphology

- Tiny Gram-negative coccobacillus
- Facultative intracellular: macrophages
- Needs cysteine to grow (chocolate agar or cysteine-enriched media)

## Transmission

- Tick and deer fly bites
- Skin contact with infected animals, especially rabbits, hares and rodents (hunters)
- Contaminated water, inhaled dust or aerosols
- No person-to-person spread; high risk in the laboratory

**Reservoir:** Rabbits, hares, rodents and ticks

**Vector:** Ticks and deer flies.

### Isolation precautions

What the care team adds to standard precautions.

- Standard

## Virulence factors

- Very low infectious dose
- Survives and multiplies in macrophages after escaping the phagosome
- Capsule that resists complement
- Considered a possible bioterrorism agent

## Diseases it causes

- Tularemia [Tularaemia →](https://durgical.com/en/conditions/tularaemia/)

## Clinical picture

- Ulceroglandular, the most common form: an ulcer at the entry site and large regional nodes
- Glandular, oculoglandular and oropharyngeal
- Pneumonic, from inhalation, the most severe
- Typhoidal: fever without a clear focus

## Diagnosis

- Serology
- Culture on cysteine media; warn the lab so it is handled at high biosafety level
- PCR

## Treatment

Aminoglycosides (streptomycin or gentamicin) for moderate or severe disease; alternatives: fluoroquinolones (ciprofloxacin) or doxycycline.

Drug class only; doses and regimens are set by the clinician from the current guideline.

In Pharmacology:

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

## Prevention

- Repellent and protective clothing against ticks and deer flies
- Gloves when handling sick or dead animals
- Biosafety precautions in the laboratory

## In Colombia

Tularemia occurs mainly in the Northern Hemisphere and is not a known problem in Colombia; it appears in international exams such as the USMLE.

## Memory aid

"Francisella rides rabbits and ticks": the hunter who skins the hare takes home an ulcer and a swollen node as souvenirs.

## Test yourself

Think of the answer, then tap the question to see it.

## What is the most common clinical form of tularemia?

Ulceroglandular: an ulcer at the entry site and enlarged regional nodes.

## Which animals and vectors transmit Francisella tularensis?

Rabbits, hares and rodents, and vectors such as ticks and deer flies.

## Which special nutrient does Francisella need to grow in culture?

Cysteine.

## Which antibiotic class is preferred for severe tularemia?

Aminoglycosides, such as streptomycin or gentamicin.

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## Related

- [Yersinia](https://durgical.com/en/microbiology/yersinia/)
- [Brucella](https://durgical.com/en/microbiology/brucella/)

## Related conditions

- [Tularaemia](https://durgical.com/en/conditions/tularaemia/)

## 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: Other Gram-negative rods](https://durgical.com/en/microbiology/groups/other-gram-negative-rods/)

Educational content on microorganisms; not a treatment guide and no substitute for a health professional's advice. No doses are given.

Sources: [About Tularemia](https://www.cdc.gov/tularemia/about/index.html) (CDC, 2026); [Tularemia](https://www.msdmanuals.com/professional/infectious-diseases/gram-negative-bacilli/tularemia) (MSD Manual Professional Edition, 2026).

## **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/francisella-tularensis/
License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/microbiology/francisella-tularensis/