Necrobacillosis: causes, symptoms, diagnosis, and treatment

Necrobacillosis, also known as Lemierre syndrome, is an infectious disease mostly caused by Fusobacterium necrophorum.


Causes

Fusobacterium necrophorum is widely distributed in the natural world and can be found in animal farms, contaminated swamps, and soil, as well as in the mouth, intestines, and external genitals of healthy animals. The secretions, excretions, and contaminated environment of infected animals are important sources of infection. The pathogen mainly invades the tissue through the wounded skin and mucous membrane and is disseminated to other tissues or organs through bloodstream, forming secondary necrotic lesions. The disease is more common in veterinarians, laboratory workers, and butchers who are exposed to the infected animals, but sporadic cases can also be preceded by trauma or surgery, such as abdominal surgery, tonsillectomy, and dental extraction, mostly in young adults. The disease is often sporadic or endemic.


Signs and Symptoms

Early manifestations are tonsil and throat pain, bullae, abscess, gum pain, gingival ulceration, or mandibular swelling or necrosis. Some patients may have otitis media and meningitis. Subsequently, the bacteria disseminate through bloodstream, causing septicopyemia and metastatic abscess, resulting in characteristic Lemierre syndrome, that is, systemic suppurative infection mainly manifested by septic thrombophlebitis of the internal jugular vein. Patients may develop fever, fatigue, and hepatosplenomegaly. Blood clots infected by the bacteria pass through the lung tissue, obstructing the pulmonary artery, causing circulatory disorders. If not treated promptly, the mortality rate can be as high as 60% or more.


Diagnosis

Diagnosis is mainly based on the pathogen found in the pus smear or pus and blood culture.

Diagnostic considerations include:

  • Oropharyngeal primary infection
  • Septicopyemia
  • Clinical or imaging manifestation of septic thrombophlebitis of the internal jugular vein
  • At least one distant suppurative focus

When the clinical manifestations of septic thrombophlebitis of the internal jugular vein are not obvious, computed tomography (CT) examination can be used.


Treatment

Antibiotic treatment should be given prior to available bacterial culture results. Antibiotics sensitive to Fusobacterium necrophorum and able to penetrate the abscess, such as penicillin plus metronidazole, should be selected, and the duration of treatment is at least 2 weeks. Macrolide antibiotics are not effective against this disease. If thrombosis is present, heparin or low molecular weight heparin can be used for antithrombotic therapy. Incision and drainage is necessary for the abscess.