[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Microbiology](https://durgical.com/en/microbiology/) › [Other clinically important bacteria](https://durgical.com/en/microbiology/groups/other-clinically-important-bacteria/) › Fusobacterium, Prevotella and Porphyromonas

# Fusobacterium, Prevotella and Porphyromonas

- Bacterium

## Gram-negative?

Thin wall with an outer membrane: stains pink.

- Exam priority: high

Anaerobes of the mouth and throat behind gum disease, foul-smelling lung abscesses and Lemierre syndrome, a throat infection that clots the neck vein.

Updated Nov 13, 2026

Also called: Fusobacterium necrophorum, Fusobacterium nucleatum, Prevotella melaninogenica, Porphyromonas gingivalis, Lemierre syndrome agent

## Quick facts

**Type**
Bacterium · [Other clinically important bacteria](https://durgical.com/en/microbiology/groups/other-clinically-important-bacteria/)

**Gram / shape**
Gram-negative · Fusobacterium

**Spread**
Endogenous · Aspiration of oral secretions

**Causes**
Lemierre syndrome · Peritonsillar abscess · F

On this page

- The basics Key points
- At a glance
- Morphology
- Transmission
- In Colombia
- Memory aid
- What the colours mean

- Clinical Virulence factors
- Diseases it causes
- Clinical picture
- Diagnosis

- Treatment Treatment
- Prevention

- Study Test yourself

- Connections Connections

## Key points

- Sore throat, then sepsis, neck vein thrombosis and septic lung emboli in a young adult: Lemierre syndrome (F. necrophorum).
- Aspiration lung abscess with foul sputum: oral anaerobes (Fusobacterium, Prevotella, Peptostreptococcus).
- Black-pigmented anaerobes: Prevotella melaninogenica and Porphyromonas.
- Porphyromonas gingivalis is a key periodontitis pathogen.
- Prevotella makes beta-lactamase: use a beta-lactam/inhibitor, metronidazole, a carbapenem or clindamycin.

## At a glance

**Gram**
Gram-negative

**Shape**
Fusobacterium: long thin rods with tapered ends; Prevotella and Porphyromonas: short pleomorphic rods

**Oxygen**
Obligate anaerobes

**Family**
Fusobacteriaceae, Prevotellaceae, Porphyromonadaceae

## Morphology

- Gram-negative anaerobic rods; Fusobacterium nucleatum has pointed, spindle-shaped ends
- Prevotella melaninogenica and Porphyromonas form brown to black pigmented colonies
- Grow only in anaerobic conditions; pus smells foul

## Transmission

- Endogenous: they come from the patient's own mouth, throat, gut or genital tract
- Aspiration of oral secretions, dental infection, sore throat or human bites
- Not spread from person to person

**Reservoir:** Gingival crevices, tonsils and oropharynx; also gut and vagina

### Isolation precautions

What the care team adds to standard precautions.

- Standard

## Virulence factors

- F. necrophorum: leukotoxin and haemagglutinin; it aggregates platelets and promotes septic thrombophlebitis
- Fusobacterium lipopolysaccharide is a potent endotoxin (shock, disseminated intravascular coagulation)
- P. gingivalis: gingipain proteases that destroy periodontal tissue
- Many Prevotella strains make beta-lactamase, so penicillin alone fails

## Diseases it causes

- Lemierre syndrome: pharyngitis, septic thrombophlebitis of the internal jugular vein and septic emboli [Deep neck infection and Ludwig angina →](https://durgical.com/en/conditions/deep-neck-infection-and-ludwig-angina/)
- Peritonsillar abscess and severe pharyngitis in adolescents and young adults [Peritonsillar abscess →](https://durgical.com/en/conditions/peritonsillar-abscess/)
- Aspiration pneumonia [Aspiration pneumonia and pneumonitis →](https://durgical.com/en/conditions/aspiration-pneumonia-and-pneumonitis/)
- Lung abscess and empyema [Lung abscess →](https://durgical.com/en/conditions/lung-abscess/)
- Periodontitis and necrotizing gingivitis (Vincent angina, with spirochetes) [Periodontitis →](https://durgical.com/en/conditions/periodontitis/)
- Brain abscess from dental, sinus or ear infection [Brain abscess →](https://durgical.com/en/conditions/brain-abscess/)
- F. nucleatum is found in colorectal tumours; its causal role is still under study [Colorectal cancer →](https://durgical.com/en/conditions/colorectal-cancer/)

## Clinical picture

- Lemierre: a healthy young adult with a sore throat who days later has rigors, tender swelling along the neck and multiple cavitating lung nodules
- Septic emboli may also reach joints, liver and brain
- Aspiration lung abscess in people with alcohol use, seizures or poor dentition; foul-smelling sputum
- Vincent angina: painful ulcerated tonsils or gums with grey pseudomembrane and very bad breath

## Diagnosis

- Anaerobic blood cultures; growth can be slow
- Contrast-enhanced CT of the neck shows internal jugular vein thrombosis; chest CT shows septic emboli
- Pus aspirated and sent in anaerobic transport; Gram stain shows mixed Gram-negative rods
- PCR detects F. necrophorum when cultures fail

## Treatment

Drainage of pus plus antibiotics active against anaerobes: metronidazole (combined with a beta-lactam for streptococci), a beta-lactam/beta-lactamase inhibitor (ampicillin-sulbactam, amoxicillin-clavulanic acid, piperacillin-tazobactam), a carbapenem, or clindamycin for oral infections. Penicillin alone is unreliable because of beta-lactamase; anticoagulation in Lemierre syndrome is debated.

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

In Pharmacology:

- [Metronidazole](https://durgical.com/en/pharmacology/metronidazole/)
- [Ampicillin + sulbactam](https://durgical.com/en/pharmacology/ampicillin-sulbactam/)
- [Amoxicillin + clavulanic acid](https://durgical.com/en/pharmacology/amoxicillin-clavulanic-acid/)
- [Clindamycin](https://durgical.com/en/pharmacology/clindamycin/)
- [Piperacillin + tazobactam](https://durgical.com/en/pharmacology/piperacillin-tazobactam/)
- [Meropenem](https://durgical.com/en/pharmacology/meropenem/)

## Prevention

- Oral hygiene and regular dental care
- Aspiration precautions: upright position and swallowing assessment in at-risk patients
- Early review of a sore throat that worsens with rigors or neck pain

## In Colombia

These infections are not an individual notifiable event in Colombia; Lemierre syndrome is rare and is recognised by clinical suspicion in young people with a severe sore throat followed by sepsis.

## Memory aid

Lemierre follows the «throat-neck-lung» staircase: first the tonsil, then the jugular vein, then the lungs fill with little cavities.

## Test yourself

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

## Which organism causes most cases of Lemierre syndrome?

Fusobacterium necrophorum, an anaerobic Gram-negative rod.

## Which vein is involved in Lemierre syndrome?

The internal jugular vein, with septic thrombophlebitis.

## Why may penicillin alone fail in oral anaerobic infections?

Many Prevotella and some Fusobacterium strains produce beta-lactamase.

## Which anaerobes form black-pigmented colonies?

Prevotella melaninogenica and Porphyromonas species.

## Which imaging test confirms internal jugular vein thrombosis in Lemierre syndrome?

Contrast-enhanced CT of the neck (ultrasound is less sensitive).

[Add to my cards (5)](https://durgical.app/estudiar/?add=/en/microbiology/fusobacterium-prevotella-and-porphyromonas/)

## 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.

## Connections

## Related 5

- [Bacteroides fragilis](https://durgical.com/en/microbiology/bacteroides-fragilis/)
- [Anaerobic Gram-positive cocci](https://durgical.com/en/microbiology/anaerobic-gram-positive-cocci/)
- [Streptococcus anginosus group](https://durgical.com/en/microbiology/streptococcus-anginosus-group/)
- [Actinomyces israelii](https://durgical.com/en/microbiology/actinomyces-israelii/)
- [Epstein–Barr virus](https://durgical.com/en/microbiology/epstein-barr-virus/)

## Related conditions 7

- [Deep neck infection and Ludwig angina](https://durgical.com/en/conditions/deep-neck-infection-and-ludwig-angina/)
- [Peritonsillar abscess](https://durgical.com/en/conditions/peritonsillar-abscess/)
- [Aspiration pneumonia and pneumonitis](https://durgical.com/en/conditions/aspiration-pneumonia-and-pneumonitis/)
- [Lung abscess](https://durgical.com/en/conditions/lung-abscess/)
- [Periodontitis](https://durgical.com/en/conditions/periodontitis/)
- [Brain abscess](https://durgical.com/en/conditions/brain-abscess/)
- [Colorectal cancer](https://durgical.com/en/conditions/colorectal-cancer/)

[← Back to the group: Other clinically important bacteria](https://durgical.com/en/microbiology/groups/other-clinically-important-bacteria/)

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

Sources: [Lemierre's Syndrome in the 21st Century: A Literature Review](https://pmc.ncbi.nlm.nih.gov/articles/PMC10505273/) (Cureus, 2023); [Mixed Anaerobic Infections - Infectious Disease - MSD Manual Professional Edition](https://www.msdmanuals.com/professional/infectious-diseases/anaerobic-bacteria/mixed-anaerobic-infections) (MSD Manual Professional Edition, 2025).

## **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.

---
Source: https://durgical.com/en/microbiology/fusobacterium-prevotella-and-porphyromonas/
License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/microbiology/fusobacterium-prevotella-and-porphyromonas/