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Fusobacterium novum in liquid culture
Scientific classification e
Domain: Bacteria
Phylum: Fusobacteriota
Class: Fusobacteriia
Order: Fusobacteriales
Family: Fusobacteriaceae
Staley and Whitman 2012
Genus: Fusobacterium
Knorr 1923
Type species
Fusobacterium nucleatum
Knorr 1923

Fusobacterium is a genus of obligate anaerobic, Gram-negative,[2] non-sporeforming bacteria[3] belonging to Gracilicutes. Individual cells are slender, rod-shaped bacilli with pointed ends.[4][5] Fusobacterium was discovered in 1900 by Courmont and Cade and is common in the flora of humans.[6][7]

Strains of Fusobacterium can cause several human diseases and infections, including periodontal diseases, Lemierre's syndrome,[8] oral, head, and neck infections, as well as colorectal cancer and topical skin ulcers.[9]

It has also been tied to HIV infection and suboptimal immune recovery.[10] Detection of Fusobacterium is typically through surgical retrieval of tissue as well as testing of fecal matter and blood given the patient is showing symptoms.[2] Early detection is preferred and best to avoid further development.[11]

Although older sources state that Fusobacterium is part of the normal flora of the human oropharynx, the current consensus is that Fusobacterium should always be treated as a pathogen.[12] Fusobacterium currently has 13 strains; the main one affecting humans is F. nucleatum[13] while F. necrophorum follows as well as affecting animals, mainly cattle.[14]


Fusobacterium is a anaerobic gram-negative bacteria, which is also nonmotile and nonsporulating; whose most common species are F. nucleatum, as well as, F. necrophorum[7][15]

Pathogenic species

F. nucleatum is found in humans more so than any other species of Fusobacterium.[13] It is commonly found in the oral cavity as well as in the intestinal tract.[9] Some of its pathogenic ties include its extraction from amniotic fluid sourced from spontaneous premature labor without reason/a given source.[13] A few additional sources of its pathogenic nature inclue its association with oral inflammation diseases, cancers such as pancreatic, oral, and colorectal, as well as infections of the head and neck. This association is due to the high increase in the prevalence of F. nucleatum in those infected areas. F. nucleatum can worsen or initiate colorectal cancer by stimulating other Gram-negative bacteria such as Streptococcus, Campylobacter spp. and Leptotrichia as well as cancerous gene expression from Beta-catenin signaling. F. nucleatum can be detected in tissues, genomic DNA, and feces using methods such as (FQ, q, and dd) polymerase chain reaction and fluorescence in situ hybridization. However, these are limited because tissues can only be tested after surgery and fecal matter can return false positive results.[9]

F. necrophorum has been found as a common pathogen in the diagnostic of peritonsillar abscess and is more prevalent than other bacteria regarding this infection. It is also the most frequent leading cause associated with Lemierre Syndrome and is not proven to be a normal part of the human oral bacterium population.[8] F. necrophorum commonly infects animals, causing liver abscesses and necrodic diseases, and can combine with other pathogenic bacteria to cause various infections such as foot rot[14] and uterine infections.[16]

Sources of other species of Fusobacterium [13]

  • F. ulcerans is very similar to F. varium and is commonly extracted from tropical ulcers.
  • F. necrogenes is also closely related to F. ulcerans and F. varium and has been found in chickens and ducks.
  • F. perfoetans is sourced from fecal matter. (F. perfoetans and F. necrogenes have not been sourced from any infections in humans or animals)
  • F. gonidiaformans is typically found in the intestines of humans and is not found orally like the other Fusobacterium.
  • F. russi is a common bacteria in canine and feline oral cavities and can lead to the infection of puncture wounds if transferred to humans from bites.
  • F. simae which can be sourced from monkeys.


Current species

Fusobacterium is divided into 13 different species, two of which each have their own set of subspecies (F. nucleatum and F. necrophorum).[13]

  • F. nucleatum
  • F. necrophorum
  • F. periodonticumm
  • F. naviforme
  • F. simae
  • F. gonidiaformans
  • F. aequinum
  • F. ulcerans
  • F. varium
  • F. mortiferum
  • F. necrogenes
  • F. russii
  • F. perfoetans

Reclassified species

Other previously declared species of Fusobacterium such as F. symbiosum, F. praecutum, F. plauti, F. alocis, F. sulci, and F. prausnitzii have since been reclassified due to containing different characteristics from the other Fusobacterium members. F. alocis has been reclassified into Filifactor alocis while F. sulci has been reclassified as Eubacterium sulci. F. prausnitzii is a part of the Clostridium leptum subgroup under Eubacterium-like organisms.[13] A few strains F. prausnitzii, a gut commensal associated with healthy patients, was completely reclassified as Faecalibacterium (Clostridiales:Ruminococcaceae) in 2002.

Phylogenic tree

16S rRNA based LTP_12_2021[17][18][19] GTDB 07-RS207 by Genome Taxonomy Database[20][21][22]

F. perfoetens

F. gonidiaformans

F. equinum Dorsch et al. 2001

F. necrophorum

F. n. funduliforme Hallé 1898 ex Shinjo et al. 1991

F. n. necrophorum (Flügge 1886) Shinjo et al. 1991

F. ulcerans

F. varium

F. mortiferum

F. necrogenes

F. gastrosuis De Witte et al. 2017

F. russii

F. periodonticum

F. polymorphum

F. naviforme (Jungano 1909) Moore & Holdeman 1970

F. vincentii

F. canifelinum

F. nucleatum

F. simiae Slots and Potts 1982

Filifactor alocis (Cato et al. 1985) Jalava and Eerola 1999

F. animalis

F. watanabei Tomida et al. 2021

Fusobacterium perfoetens (Tissier 1905) Moore and Holdeman 1973

Cetobacterium Foster et al. 1996


F. ulcerans Adriaans and Shah 1988

F. varium (Eggerth and Gagnon 1933) Moore and Holdeman 1969

"Ca. F. pullicola" Gilroy et al. 2021

F. mortiferum (Harris 1901) Moore and Holdeman 1970

F. necrogenes (Weinberg et al. 1937) Moore and Holdeman 1970

F. gonidiaformans (Tunnicliff and Jackson 1925) Moore and Holdeman 1970

F. necrophorum (Flügge 1886) Shinjo et al. 1991

F. russii (Hauduroy et al. 1937) Moore and Holdeman 1970

"F. massiliense" Mailhe et al. 2017

F. periodonticum Slots et al. 1984

"F. pseudoperiodonticum" Park et al. 2019

F. animalis (Gharbia & Shah 1992) Kook et al. 2022

F. vincentii (Dzink, Sheenan & Socransky 1990) Kook et al. 2022

F. nucleatum Knorr 1922 (type sp.)

F. canifelinum corrig. Conrads et al. 2004

"F. hwasookii" Cho et al. 2014

F. polymorphum (Dzink, Sheenan & Socransky 1990) Kook et al. 2022

Clinical relevance

Fusobacterium is often associated with ulcerative colitis.[23] Research of colon cancer has also shown an overrepresentation of Fusobacterium, both in feces of patients[24] and tumor issue itself.[25] Fusobacterium has also been seen increased in individuals infected with HIV as well as in individuals with suboptimal immune recovery as compared to patients who were not infected and had optimal responses.[10]

Symptoms and signs

Fusobacterium infections often cause clinical symptoms such as a fever, inflammation, and a diseased appearance.[citation needed]


a,b)Representative fluorescence in situ hybridization targeting Fusobacterium sp. in colorectal mucosal biopsy sections using bacterial 16S rRNA probes

Diagnosis can confirm suspicions of Fusobacterium infection through blood testing or culturing the tissue. Upon diagnosing the infection, action to treat it involves the application of antibiotics over a 2-week period which could be in the form of penicillin or other variants as well as using anaerobic antibiotics like clindamycin and metronidazole which work when the Fusobacterium can break down the Beta-lactams. Leaving Fusobacterium untreated could lead to more severe developments of the infection and early testing is recommended.[2] By testing early, fatal diseases such as Lemierre syndrome can be avoided. However, this requires the family physician to be conscious of the danger as infections such as Lemierre syndrome affects younger populations and especially those of male gender.[11]


The bacterium is a big anchor for biofilms.[26][27] It is usually susceptible to clindamycin,[28] while approximately 20% of the clinical strains are resistant to penicillin.[29] In contrast to Bacteroides spp., Fusobacterium has a potent lipopolysaccharide.


Courmont and Cade discovered Fusobacterium in 1900.[6] However, the first documented infection of Fusobacterium was in 1898 by Veillon and Zuber, which included a human systemic infection of a young child.[30] However, the genus was not proposed until Knorr in 1923.[31] Fusobacterium is not alien and is actually a normal part of every human's oral, gastrointestinal, and (female) genital flora which is why infections are not commonly seen.[7]

See also


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  2. 2.0 2.1 2.2 Arane, Karen; Goldman, Ran (October 2016). "Fusobacterium infections in children". National Library of Medicine. Archived from the original on 2 May 2023. Retrieved 1 May 2023.
  3. Broadley, Marissa; Schweon, Steven J. (May 2017). "Get the facts about Fusobacterium". Nursing2023. 47 (5): 64. doi:10.1097/01.NURSE.0000515524.23032.d5. ISSN 0360-4039. Archived from the original on 2023-05-14. Retrieved 2023-05-31.
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  7. 7.0 7.1 7.2 Garcia-Carretero, Rafael; Lopez-Lomba, Marta; Carrasco-Fernandez, Blanca; Duran-Valle, Maria Teresa (October 2017). "Clinical Features and Outcomes of Fusobacterium Species Infections in a Ten-Year Follow-up". National Library of Medicine. Archived from the original on May 14, 2023. Retrieved May 13, 2023.
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  9. 9.0 9.1 9.2 Shang, Fu-Mei; Liu, Hong-Li (15 March 2018). "Fusobacterium nucleatum and colorectal cancer: A review". World Journal of Gastrointestinal Oncology. 10 (3): 71–81. doi:10.4251/wjgo.v10.i3.71.
  10. 10.0 10.1 Lee, Soo Ching; Chua, Ling Ling; Yap, Siew Hwei; Khang, Tsung Fei; Leng, Chan Yoon; Raja Azwa, Raja Iskandar; Lewin, Sharon R.; Kamarulzaman, Adeeba; Woo, Yin Ling; Lim, Yvonne Ai Lian; Loke, P’ng; Rajasuriar, Reena (2018-09-24). "Enrichment of gut-derived Fusobacterium is associated with suboptimal immune recovery in HIV-infected individuals". Scientific Reports. 8 (1): 14277. doi:10.1038/s41598-018-32585-x. ISSN 2045-2322. Archived from the original on 2023-05-04. Retrieved 2023-05-31.
  11. 11.0 11.1 Cheung, Winson (September 2007). "Fusobacterium". National Library of Medicine. Archived from the original on 2 May 2023. Retrieved 1 May 2023.
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  13. 13.0 13.1 13.2 13.3 13.4 13.5 Citron, Diane (September 2002). "Update on the Taxonomy and Clinical Aspects of the Genus Fusobacterium". Clinical Infectious Diseases. 35 (s1): S22–S27. doi:10.1086/341916. Archived from the original on 24 April 2023. Retrieved 5 May 2023.
  14. 14.0 14.1 Tadepalli, S.; Narayanan, S. K.; Stewart, G. C.; Chengappa, M. M.; Nagaraja, T. G. (2009-02-01). "Fusobacterium necrophorum: A ruminal bacterium that invades liver to cause abscesses in cattle". Anaerobe. Foodborne and Gastrointestinal Pathogen Ecology and Control in the Intestinal Tract. 15 (1): 36–43. doi:10.1016/j.anaerobe.2008.05.005. ISSN 1075-9964.
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