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Fusobacterium USMLE Notes & Mnemonics contains all the high-yield points you need to know.


  • Fusobacterium: A genus of anaerobic, non-spore-forming, Gram-negative bacteria, implicated in various human infections.

Pathogenic Species:

  • Fusobacterium necrophorum: Often associated with Lemierre’s syndrome.
  • Fusobacterium nucleatum: Linked to periodontal diseases, and also found in other infections.

Clinical Associations:

  1. Lemierre’s Syndrome:
    • Caused by Fusobacterium necrophorum.
    • Begins as oropharyngeal infection. (Ref)
    • Leads to thrombophlebitis of the internal jugular vein and septic emboli.
    • Presents with sore throat, fever, and swelling in the neck.
    • Can lead to metastatic infections, particularly in the lungs.
  2. Periodontal Disease:
    • Fusobacterium nucleatum is a key pathogen in gingivitis and periodontitis.
    • Contributes to plaque formation and gum disease.
  3. Other Infections:
    • Abdominal infections.
    • Skin and soft tissue infections.
    • Pulmonary infections.


  • Culture: Grows in anaerobic conditions.
  • PCR: Can be used for specific identification.
  • Imaging: For Lemierre’s syndrome, ultrasound or CT scan to detect jugular vein thrombosis.


  • Antibiotics: Effective against anaerobes (e.g., metronidazole, clindamycin, carbapenems).
  • Lemierre’s Syndrome: Prolonged antibiotic therapy; sometimes anticoagulation.
  • Dental Infections: Oral hygiene improvement, specific dental treatments, and antibiotics.

Mnemonic: “FUSO

  • Fusobacterium
  • Unusual (anaerobic, Gram-negative)
  • Sore throat progressing to Lemierre’s
  • Oral cavity (periodontal disease association)

Chart: Key Features of Fusobacterium Infections

FeatureLemierre’s SyndromePeriodontal Disease
Causative AgentFusobacterium necrophorumFusobacterium nucleatum
Clinical PresentationSore throat, neck swelling, sepsisGum inflammation, plaque formation
ComplicationsSeptic emboli, mainly in lungsTooth loss, systemic effects
DiagnosisCulture, imaging (CT, ultrasound)Clinical examination, dental X-rays
TreatmentProlonged antibiotics, sometimes anticoagulationOral hygiene, antibiotics

Note: For the USMLE, focus on the clinical syndromes associated with Fusobacterium, particularly Lemierre’s syndrome, and their management. Understanding the anaerobic nature of these bacteria and their role in specific infections can also be tested.

Check other important USMLE Notes

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