Fusobacterium is a genus of obligate anaerobic, Gram-negative,[Taber's Cyclopedic Medical Dictionary, 22nd Edition, , (2009)n p.983] Fusobacterium was discovered in 1900 by Courmont and Cade and is common in the flora of humans.
Strains of Fusobacterium can cause several human diseases and infections, including periodontal diseases,
Lemierre's syndrome,
It has been tied to HIV infection and suboptimal immune recovery.
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.
Background
History
Although the genus was not discovered until 1900 by Courmont and Cade,
the first documented
Fusobacterium infection was reported in 1898 by Veillon and Zuber, who described a case of systemic infection in a young child.
The genus was proposed by Knorr in 1923.
has been classically considered a normal part of the human oral, gastrointestinal, and female genital flora, which is why infections are not commonly seen.
Clinical relevance
Fusobacterium is often associated with ulcerative colitis.
Research of
colon cancer has also shown an overrepresentation of
Fusobacterium, both in feces of patients
and tumor tissue itself.
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.
Prevalent pathogenic species
F. nucleatum is found in humans more so than any other species of
Fusobacterium.
It is commonly found in the oral cavity as well as in the intestinal tract.
Some of its pathogenic ties include its extraction from
amniotic fluid sourced from spontaneous
Preterm birth without reason/a given source.
A few additional sources of its pathogenic nature include its association with oral inflammation diseases, cancers such as pancreatic,
Oral cancer, 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 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.
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.
Sources of other species of Fusobacterium
Source:
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F. ulcerans is very similar to F. varium and is commonly extracted from .
-
F. necrogenes is also closely related to F. ulcerans and F. varium and has been found in chickens and ducks.
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F. perfoetans is sourced from fecal matter. ( F. perfoetans and F. necrogenes have not been sourced from any infections in humans or animals)
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F. gonidiaformans is typically found in the intestines of humans and is not found orally like the other Fusobacterium.
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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.
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F. simae which can be sourced from monkeys.
Symptoms and treatment
Fusobacterium infections often cause clinical symptoms such as a fever, inflammation, and a diseased appearance. Further 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
. Leaving
Fusobacterium untreated could lead to more severe developments of the infection and early testing is recommended.
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.
The bacterium is a big anchor for biofilms.
It is usually susceptible to
clindamycin,
while approximately 20% of the clinical strains are resistant to
penicillin.
In contrast to
Bacteroides spp.,
Fusobacterium has a potent lipopolysaccharide.
Taxonomy
Current species
Fusobacterium is divided into 13 different species, two of which each have their own set of subspecies (
F. nucleatum and
F. necrophorum).
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.
A few strains
F. prausnitzii, a gut commensal associated with healthy patients, was completely reclassified as
Faecalibacterium (
Clostridiales:
Ruminococcaceae) in 2002.
Phylogenic tree
See also
-
Altered Schaedler flora
-
List of bacteria genera
-
List of bacterial orders
External links
