Fusobacterium

Overview
Fusobacterium is a genus of filamentous, anaerobic, Gram-negative bacteria, similar to Bacteroides. Fusobacterium contribute to several human diseases, including periodontal diseases, Lemierre's syndrome, and tropical skin ulcers. Although older resources have stated that Fusobacterium is a common occurrence in the human oropharynx, the current consensus is that Fusobacterium should always be treated as a pathogen.

F. Necrophorum
Fusobacterium necrophorum is the species of Fusobacterium that is responsible for Lemierre's syndrome, and appears to be responsible for 10% of all acute sore throats and 21% of all recurring sore throats, with the remainder being caused by Group A streptococci or viruses.

Other complications from F. necrophorum include meningitis, complicated by thrombosis of the cerebral veins, and infection of the urogenital and the gastrointestinal tracts.

F. necrophorum infection usually responds to treatment with penicillin or metronidazole, but penicillin treatment for persistent pharyngitis appears anecdotally to have a higher relapse rate, although the reasons for that are unclear. This bacterium is also considered the cause of the foot disease thrush in horses.

Although this infection is rare, researchers agree that this diagnosis should be considered in a septicaemic patient with thrombosis in an unusual site, and underlying malignancy should be excluded in cases of confirmed F. necrophorum occurring at sites caudal to the head.

F. Nucleatum
Fusobacterium Nucleatum is an oral bacterium, indigenous to the human oral cavity, that plays a role in periodontal disease. This organism is commonly recovered from different monomicrobial and mixed infections in humans and animals. It is a key component of periodontal plaque due to its abundance and its ability to coaggregate with other species in the oral cavity.

F. Polymorphum
Fusobacterium Polymorphum is a bacterium that has been isolated from the gingival crevice in humans, and has been implicated in the immunopathology of periodontal disease. It has also been isolated in guinea pigs in research studies.