DurgicalDurgical
EN
Open the app

Microbiology · 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

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

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:

Prevention

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

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.

Add to my cards (4)

← Back to the group: 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 (CDC, 2026); 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.