Microbiology & infectious diseases

Gram negative bacteria

Fusobacterium necrophorum

Deputy Editor-in-Chief: Patricia Tsang, M.D., M.B.A.
Thomas Cotter, D.O.
Hasan Samra, M.D.

Last author update: 24 May 2022
Last staff update: 24 May 2022

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PubMed Search: Fusobacterium necrophorum

Thomas Cotter, D.O.
Hasan Samra, M.D.
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Cite this page: Cotter T, Samra H. Fusobacterium necrophorum. PathologyOutlines.com website. http://www.pathologyoutlines.com/topic/microbiologyfnecrophorum.html. Accessed June 16th, 2024.
Definition / general
  • Gram negative anaerobe; common oropharyngeal pathogen
  • Taxonomy: genus Fusobacterium, species necrophorum, subspecies necrophorum / fundiliforme (GMS Infect Dis 2018;6:Doc03)
Essential features
  • Gram negative, rod shaped, obligate anaerobe; nonspore forming, nonmotile
  • Most common causal agent of Lemierre syndrome; oropharyngeal infection leads to septic thrombophlebitis of the internal jugular vein
  • Debated if commensal or exogenous invader of orophopharynx (Anaerobe 2006;12:165, Anaerobe 2015;34:120)
  • Lemierre syndrome: invasive F. necrophorum disease, postanginal sepsis, necrobacillosis
  • Historical: nekrosebazillus (Anaerobe 2006;12:165)
  • Postanginal: following a purulent pharyngitis or peritonsillar abscess
  • Oropharyngeal: acute tonsillitis, peritonsillar abscess
    • Tonsillitis, historically called angina tonsillaris, hence postanginal sepsis
  • Head and neck: acute otitis
    • Spread to meninges / meningitis
  • Female urogenital tract
  • Metastasis from septic thrombophlebitis of the internal jugular vein
    • Lungs: pneumonia from septic pulmonary emboli
    • Joints: septic arthritis
    • Heart: endocarditis (mortality: 75%) (Anaerobe 2015;34:120)
  • Lemierre syndrome:
    • F. necrophorum invades into adjacent internal jugular vein and causes nidus of septic thrombophlebitis (leukotoxin induces thrombosis by aggregating platelets) (Infect Immun 2002;70:4609)
    • Thromboemboli travel hematogenously, causing pneumonia / pleural empyema / distant metastatic lesions (J Microbiol Immunol Infect 2020;53:513)
  • Virulence factors:
    • Endotoxins: lipopolysaccharide (LPS) in the cell wall, coagulase enzyme
    • Exotoxins: leukotoxin, hemolysin, lipase (Anaerobe 2006;12:165)
Diagrams / tables

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Lemierre syndrome pathophysiology

Lemierre syndrome pathophysiology

Clinical characteristics of Lemierre syndrome

Clinical characteristics of Lemierre syndrome

Clinical features
  • Lemierre syndrome: multistep disease progression
    • Pharyngitis / tonsillitis: sore throat, cervical lymphadenopathy
    • F. necrophorum local invasion of tissue / internal jugular vein (IJV): tender neck, high fever, rigors
    • IJV thromboemboli seed other organs: cavitating pulmonary infarcts, septic arthritis, soft tissue infection / abscesses, endocarditis, meningitis
    • Thrombocytopenia, sepsis / septic shock (J Clin Microbiol 2017;55:1147, Clin Microbiol Infect 2020;26:1089.e7)
  • Invasive infections:
  • Criteria for Lemierre syndrome:
    • Tonsillitis / pharyngitis in the preceding 4 weeks
    • Metastatic lesions in lungs or another site
    • Internal jugular vein thrombophlebitis or isolation of F. necrophorum or Fusobacterium sp. from a normally sterile site
  • Imaging: CT / MRI / US internal jugular vein thrombophlebitis
  • Anaerobic growth in routine culture conditions, 37 °C
  • Fastidious anaerobe agar (FAA) or blood agar / vitamin K / hemin / menadione
  • Pale yellow, round, smooth colonies, fluoresce green-yellow under long wave UV
  • Produces butyric acid from glucose: smells like overcooked cabbage or rancid butter (Anaerobe 2006;12:165)
  • Beta hemolytic
  • Positive: indole, lipase
  • Negative: catalase, hydrogen sulfide, esculin
  • MALDI TOF mass spectrometry, 16S rDNA sequencing, PCR targeting rpoB gene (Anaerobe 2016;42:89)
Case reports
  • Antibiotics: beta lactam agents (penicillins), metronidazole
  • Surgery: debridement and drainage of abscesses (Cureus 2021;13:e18436)
Clinical images

Contributed by Hasan Samra, M.D.
Culture media

Culture media

Microscopic (histologic) description
Microscopic (histologic) images

Contributed by Hasan Samra, M.D.
Gram stain

Gram stain

Board review style question #1
A 22 year old woman presented to the emergency department with a sore throat. She now has pain with swallowing and was found to have a left tonsillar abscess. PCR for group A strep (Streptococcus pyogenes) was negative. The abscess was drained and sent for aerobic and anaerobic bacterial cultures. Culture grew Fusobacterium necrophorum. What is true about this organism?

  1. Associated with Lemierre syndrome
  2. Gram positive cocci on Gram stain
  3. Indole negative
  4. The organism is obligate aerobe
Board review style answer #1
A. Associated with Lemierre syndrome. Fusobacterium necrophorum is a strict anaerobic, pleomorphic, gram negative bacillus. The organism is catalase negative and indole positive.

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Reference: Fusobacterium necrophorum
Board review style question #2

The clinical microbiology laboratory has isolated a gram negative rod from the blood culture of a young patient admitted with suspected septic thrombophlebitis. The isolate forms a pale yellow colony with slight level of hemolysis on complete blood count agar and produces a blue spot when placed on filter paper and treated with indole. Which of the following is the organism?

  1. Bacteroides fragilis
  2. Fusobacterium necrophorum
  3. Klebsiella pneumoniae
  4. Streptococcus pyogenes
Board review style answer #2
B. Fusobacterium necrophorum. The patient presentation is consistent with that of Lemierre syndrome. Fusobacterium necrophorum is strict anaerobic and indole positive. While Bacteroides fragilis is an anaerobic gram negative bacillus, it is indole negative. Streptococcus pyogenes is a gram positive coccus and Klebsiella pneumoniae is a facultative anaerobe.

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Reference: Fusobacterium necrophorum
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