Fusobacterium species are anaerobic Gram-negative bacilli, strongly associated with Vincent’s angina (acute necrotising ulcerative gingivitis) and Lemierre’s syndrome (post-anginal septic thrombophlebitis of the internal jugular vein).
Although part of the normal oral and gut flora, they can become highly pathogenic under favourable conditions (poor oral hygiene, immunosuppression, throat infections).

🔬 Characteristics

Slender Gram-negative rods with tapered/pointed ends.
Strict anaerobes, thriving in low-oxygen environments.
Often foul-smelling due to production of volatile fatty acids.

🧾 Types

F. necrophorum – classic cause of Lemierre’s syndrome in adolescents and young adults following tonsillitis/pharyngitis.
F. nucleatum – implicated in periodontal disease, dental sepsis, and occasionally intra-abdominal abscesses.

🌍 Source

Normal commensals of the oropharynx, GI tract, and genital tract.
Opportunistic pathogens when mucosal barriers are breached.

⚔️ Pathogenicity

Vincent’s angina (Trench mouth): Acute necrotising gingivitis with painful bleeding gums, halitosis, fever, and ulceration. Often co-infection with spirochaetes.
Lemierre’s syndrome: Begins as pharyngitis → spreads to peritonsillar tissue → septic thrombophlebitis of the internal jugular vein → septic emboli (esp. lungs, liver, brain). Mortality up to 10% even with treatment.
Abscess formation: Frequently causes head, neck, and chest abscesses (pleural empyema, liver abscess).
Septicaemia: May progress rapidly, especially in immunocompromised patients.

🧪 Investigations

Blood cultures – may take time as they are slow-growing strict anaerobes.
Imaging (CT neck/chest) – crucial in suspected Lemierre’s syndrome to identify IJV thrombosis and pulmonary septic emboli.
Oral exam – necrotic, ulcerated gingivae with halitosis in Vincent’s angina.

💊 Resistance

Usually susceptible to most beta-lactams, but some strains produce beta-lactamases (→ penicillin resistance).
Metronidazole remains reliably effective against anaerobes.

🩺 Management

Antibiotics:
- First-line: Metronidazole.
- Alternatives: Clindamycin or amoxicillin–clavulanate.
- Severe/systemic disease: Piperacillin–tazobactam or Carbapenems.
Surgical drainage – indicated for abscesses or empyema.
Lemierre’s syndrome: Requires early recognition, IV antibiotics (often prolonged), surgical drainage if abscess, and consideration of anticoagulation for internal jugular thrombosis (controversial).

📌 Key Facts

Exam pearl: A previously healthy young adult with sore throat → recovers → 1 week later develops septic shock + cavitating pulmonary lesions → think Lemierre’s syndrome (F. necrophorum).
Vincent’s angina is strongly linked to poor oral hygiene, malnutrition, and stress (“trench mouth” of WWI).

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Fusobacterium

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