''Fusobacterium'' is a genus of obligate

anaerobic Anaerobic means "living, active, occurring, or existing in the absence of free oxygen", as opposed to aerobic which means "living, active, or occurring only in the presence of oxygen." Anaerobic may also refer to: *Adhesive#Anaerobic, Anaerobic ad ...

Gram-negative Gram-negative bacteria are bacteria that, unlike gram-positive bacteria, do not retain the crystal violet stain used in the Gram staining method of bacterial differentiation. Their defining characteristic is that their cell envelope consists ...

, non-sporeforming bacteria belonging to

Gracilicutes Gracilicutes (Latin: ''gracilis'', slender, and ''cutis'', skin, referring to the cell wall) is a clade in bacterial phylogeny. Traditionally gram staining results were most commonly used as a classification tool, consequently until the advent o ...

. Individual

cell Cell most often refers to: * Cell (biology), the functional basic unit of life * Cellphone, a phone connected to a cellular network * Clandestine cell, a penetration-resistant form of a secret or outlawed organization * Electrochemical cell, a de ...

s are slender, rod-shaped

bacilli Bacilli is a Taxonomy (biology), taxonomic Class (biology), class of bacteria that includes two orders, Bacillales and Lactobacillales, which contain several well-known pathogens such as ''Bacillus anthracis'' (the cause of anthrax). ''Bacilli'' ...

with pointed ends. ''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 disease Periodontal disease, also known as gum disease, is a set of inflammatory conditions affecting the tissues surrounding the teeth. In its early stage, called gingivitis, the gums become swollen and red and may bleed. It is considered the main c ...

Lemierre's syndrome Lemierre's syndrome is infectious thrombophlebitis of the internal jugular vein. It most often develops as a complication of a bacterial sore throat infection in young, otherwise healthy adults. The thrombophlebitis is a serious condition and may ...

, oral, head, and neck infections, as well as

colorectal cancer Colorectal cancer (CRC), also known as bowel cancer, colon cancer, or rectal cancer, is the development of cancer from the Colon (anatomy), colon or rectum (parts of the large intestine). Signs and symptoms may include Lower gastrointestinal ...

and topical

skin ulcers An ulcer is a sore on the skin or a mucous membrane, accompanied by the disintegration of tissue. Ulcers can result in complete loss of the epidermis and often portions of the dermis and even subcutaneous fat. Ulcers are most common on the skin o ...

. It has been tied to

HIV infection The human immunodeficiency virus (HIV) is a retrovirus that attacks the immune system. Without treatment, it can lead to a spectrum of conditions including acquired immunodeficiency syndrome (AIDS). It is a preventable disease. It can ...

and suboptimal immune recovery. Detection of ''Fusobacterium'' is typically through surgical retrieval of tissue, fecal tests, or blood tests in patients showing symptoms. Early detection is preferred and helps to prevent further disease progression. Although older sources state that ''Fusobacterium'' is part of the normal flora of the human

oropharynx The pharynx (: pharynges) is the part of the throat behind the mouth and nasal cavity, and above the esophagus and trachea (the tubes going down to the stomach and the lungs respectively). It is found in vertebrates and invertebrates, though its ...

, the current consensus is that ''Fusobacterium'' should always be treated as a pathogen. There are thirteen described ''Fusobacterium'' strains; the predominant one affecting humans is '' F. nucleatum'', followed by '' F. necrophorum'', which also affects animals, mainly cattle.

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. ''Fusobacterium'' 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 Ulcerative colitis (UC) is one of the two types of inflammatory bowel disease (IBD), with the other type being Crohn's disease. It is a long-term condition that results in inflammation and ulcers of the colon and rectum. The primary sympto ...

. Research of

colon cancer Colorectal cancer (CRC), also known as bowel cancer, colon cancer, or rectal cancer, is the development of cancer from the colon or rectum (parts of the large intestine). Signs and symptoms may include blood in the stool, a change in bowel ...

has also shown an overrepresentation of ''Fusobacterium'', both in feces of patients and tumor tissue itself. ''Fusobacterium'' has also been seen increased in individuals infected with

HIV The human immunodeficiency viruses (HIV) are two species of '' Lentivirus'' (a subgroup of retrovirus) that infect humans. Over time, they cause acquired immunodeficiency syndrome (AIDS), a condition in which progressive failure of the im ...

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 The amniotic fluid is the protective liquid contained by the amniotic sac of a gravid amniote. This fluid serves as a cushion for the growing fetus, but also serves to facilitate the exchange of nutrients, water, and biochemical products betwee ...

sourced from spontaneous

premature labor Preterm birth, also known as premature birth, is the Childbirth, birth of a baby at fewer than 37 weeks Gestational age (obstetrics), gestational age, as opposed to full-term delivery at approximately 40 weeks. Extreme preterm is less than 28 ...

without reason/a given source. A few additional sources of its pathogenic nature include its association with oral inflammation diseases, cancers such as

pancreatic The pancreas (plural pancreases, or pancreata) is an organ of the digestive system and endocrine system of vertebrates. In humans, it is located in the abdomen behind the stomach and functions as a gland. The pancreas is a mixed or heterocrine ...

oral The word oral may refer to: Relating to the mouth * Relating to the mouth, the first portion of the alimentary canal that primarily receives food and liquid **Oral administration of medicines ** Oral examination (also known as an oral exam or ora ...

, and

colorectal The large intestine, also known as the large bowel, is the last part of the gastrointestinal tract and of the digestive system in tetrapods. Water is absorbed here and the remaining waste material is stored in the rectum as feces before being rem ...

, 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

by stimulating other bacteria such as ''

Streptococcus ''Streptococcus'' is a genus of gram-positive spherical bacteria that belongs to the family Streptococcaceae, within the order Lactobacillales (lactic acid bacteria), in the phylum Bacillota. Cell division in streptococci occurs along a sing ...

, 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 The polymerase chain reaction (PCR) is a method widely used to make millions to billions of copies of a specific DNA sample rapidly, allowing scientists to amplify a very small sample of DNA (or a part of it) sufficiently to enable detailed st ...

and

fluorescence in situ hybridization Fluorescence ''in situ'' hybridization (FISH) is a molecular cytogenetic technique that uses fluorescent probes that bind to only particular parts of a nucleic acid sequence with a high degree of sequence complementarity. It was developed by ...

. 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. '' 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 Foot rot, also known as foul-in-the-foot, interdigital necrobacillosis or infectious pododermatitis, is a hoof infection commonly found in sheep, goats, and cattle. As the name suggests, it rots away the foot of the animal, more specifically the ...

and

uterine infection Endometritis is inflammation of the inner lining of the uterus (endometrium). Symptoms may include fever, lower abdominal pain, and abnormal vaginal bleeding or discharge. It is the most common cause of infection after childbirth. It is also pa ...

Sources of other species of ''Fusobacterium''

Source: * ''F. ulcerans'' is very similar to ''F. varium'' and is commonly extracted from

tropical ulcer Tropical ulcer, more commonly known as jungle rot, is a chronic ulcerative skin lesion thought to be caused by polymicrobial infection with a variety of microorganisms, including mycobacteria. It is common in tropical climates. Ulcers occur on ...

s. * ''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.

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 Penicillins (P, PCN or PEN) are a group of beta-lactam antibiotic, β-lactam antibiotics originally obtained from ''Penicillium'' Mold (fungus), moulds, principally ''Penicillium chrysogenum, P. chrysogenum'' and ''Penicillium rubens, P. ru ...

or other variants as well as using anaerobic antibiotics like

clindamycin Clindamycin is a lincosamide antibiotic medication used for the treatment of a number of bacterial infections, including osteomyelitis (bone) or joint infections, pelvic inflammatory disease, strep throat, pneumonia, acute otitis media (mi ...

and

metronidazole Metronidazole, sold under the brand name Flagyl and Metrogyl among others, is an antibiotic and antiprotozoal medication. It is used either alone or with other antibiotics to treat pelvic inflammatory disease, endocarditis, and bacterial vagino ...

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. 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

, while approximately 20% of the clinical strains are resistant to

. In contrast to ''

Bacteroides ''Bacteroides'' is a genus of Gram-negative, obligate anaerobic bacteria. ''Bacteroides'' species are non endospore–forming bacilli, and may be either motile or nonmotile, depending on the species. The DNA base composition is 40–48% GC. Un ...

'' spp., ''Fusobacterium'' has a potent

lipopolysaccharide Lipopolysaccharide (LPS), now more commonly known as endotoxin, is a collective term for components of the outermost membrane of the cell envelope of gram-negative bacteria, such as '' E. coli'' and ''Salmonella'' with a common structural archit ...

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 ''Filifactor alocis'' is a bacterium from the family Peptostreptococcaceae. ''F. alocis'' is an important oral organism that is associated with periodontal disease Periodontal disease, also known as gum disease, is a set of inflammatory co ...

'' while ''F. sulci'' has been reclassified as ''Eubacterium sulci. F. prausnitzii'' is a part of the '' Clostridium leptum'' subgroup under ''

Eubacterium ''Eubacterium'' is a genus of Gram-positive bacteria in the family Eubacteriaceae. These bacteria are characterised by a rigid cell wall. They may either be motile or nonmotile. If motile, they have a flagellum. A typical flagellum consists of ...

-''like organisms. A few strains ''F. prausnitzii'', a gut commensal associated with healthy patients, was completely reclassified as ''

Faecalibacterium ''Faecalibacterium'' is a genus of bacteria. The genus contains several species including ''Faecalibacterium prausnitzii'', ''Faecalibacterium butyricigenerans'', ''Faecalibacterium longum'', ''Faecalibacterium duncaniae'', ''Faecalibacterium ha ...

'' (''Clostridiales'':''Ruminococcaceae'') in 2002.

Phylogenic tree

References

External links

''Anaerobic Gram-Negative Bacilli'' chapter
in Baron's ''Medical Microbiology'' (online at the

NCBI The National Center for Biotechnology Information (NCBI) is part of the National Library of Medicine (NLM), a branch of the National Institutes of Health (NIH). It is approved and funded by the government of the United States. The NCBI is loca ...

br>bookshelf
.
''Fusobacterium''
From MicrobeWiki, the student-edited microbiology resource {{Authority control Gut flora bacteria Fusobacteriota Bacteria genera