Fusobacterium infection is rare, but possibly life-threatening infection characterized by sepsis and thrombophlebitis of the internal jugular veins, also known as termed Lemièrre's syndrome. A range of other clinical manifestations exist and various complications may arise. The diagnosis cannot be made without high clinical suspicion and proper microbiological studies.
Fusobacterium spp. (F. necrophorum and F. nucleatum) are gram-negative anaerobic bacterial microorganisms that normally reside in the human oropharynx as commensal flora  . For still unknown reasons, the infection can develop in young and healthy adults (F. necrophorum) and in the elderly population with various risk factors, most important being dialysis of neoplastic disease (F. nucleatum)  . Fusobacterium infection is most commonly encountered in the form of Lemièrre's syndrome - initial infection of the oropharynx (angina and/or tonsillitis) is followed by thrombophlebitis of the internal jugular vein and septic dissemination of the bacteria through this venous vessel   . Fusobacteria is able to reach the internal jugular vein through the lateral pharyngeal space, triggering the formation of platelet aggregates and an intense inflammatory reaction . Approximately 7 days pass from throat infection to the formation of septic emboli, which travel to the lungs and the larger joints in most cases  . Patients complain of a sore throat, pain in the neck, fever, lethargy, and poor general condition  . The infection is known to be life-threatening in the absence of early antibiotic therapy     . In addition to Lemièrre's syndrome, other infections of the head and neck (mastoiditis, sinusitis, abscess formation, and otitis, commonly seen in in the pediatric population), as well as meningitis are possible manifestations of fusobacterium infection, and organ-related signs and symptoms are noted  .
The diagnosis of fusobacterium infection is difficult to make without a thorough clinical investigation that might lead the physician toward this pathogen as the underlying cause. A detailed patient history is perhaps a pivotal step, as the initial signs and symptoms of a sore throat and subsequent deterioration can be indicative of fusobacterium infection. After a complete physical examination, imaging and microbiological studies should be employed to solidify the diagnosis. Computed tomography (CT) is recommended, as it is able to detect multiple septic emboli and confirm inflammatory lesions in the sinuses, the mastoid processes and in other organs  . Conversely, microbiological examination, principally in the form of blood cultures, is advised, but because several weeks are necessary for fusobacterium growth, more advanced methods are necessary  . For this reason, polymerase chain reaction (PCR), a procedure that detects bacterial deoxyribonucleic acid (DNA) in patient samples, should be performed whenever possible, as it carries a very good rate of diagnosis in a much faster manner than blood cultures    . Its price and the need for advanced laboratory requirement, however, limits the use of this procedure in many parts of the world in daily practice  . In spite of the challenges faced in confirming fusobacterium infection, reports have emphasized the perhaps critical role of the physician's awareness of this bacterial microorganism in the differential diagnosis, suggesting that clinical findings seen in these patients must include fusobacterium as a possible cause  .