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Get the facts about Fusobacterium

Broadley, Marissa MPH, MSEd, RN, CIC; Schweon, Steven J. MSN, MPH, RN, CIC, HEM, FSHEA, FAPIC

doi: 10.1097/01.NURSE.0000515524.23032.d5

Marissa Broadley is an infection prevention practitioner at Saratoga Hospital in Saratoga Springs, N.Y. Steven J. Schweon is an infection prevention consultant in Saylorsburg, Pa.

The authors have disclosed no financial relationships related to this article.

A RECENT CASE REPORT describes a 57-year-old man without a significant medical history who underwent a routine dental cleaning and examination.1 His oral health was unremarkable, and no invasive dental procedures were performed. Two weeks later, he presented to the hospital with tachycardia and a low-grade fever of 100.9° F (38.3° C). He had hypoactive bowel sounds and complained of right upper quadrant tenderness. Lab tests revealed leukocytosis with bandemia (“left shift”), an indication of significant inflammation and possible infection.

After blood culture specimens were obtained, I.V. metronidazole and ceftriaxone were administered. Magnetic resonance imaging demonstrated a hepatic abscess, and the patient underwent computed tomography-guided percutaneous drainage. Thirty-five milliliters of purulent fluid was obtained and sent to the lab for culture and sensitivity, which revealed Fusobacterium necrophorum (F. necrophorum), an anaerobic Gram-negative bacterium.

After receiving the culture and sensitivity test results, antibiotic therapy was changed to metronidazole and piperacillin/tazobactam. The patient responded well and was subsequently discharged. A follow-up evaluation revealed complete resolution of the hepatic abscess. The authors speculated that the oral cleaning in the dentist's office may have resulted in mucosal trauma that allowed this organism to enter the bloodstream.1

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The genus Fusobacterium is a bacilli-shaped bacterium that doesn't form spores. Because the organism is rod-shaped, with tapered ends, its name stems from the word “fusiform,” which means spindle-shaped.2Fusobacterium species are part of the normal flora of the oropharyngeal, gastrointestinal, and genital tracts.3

Modes of transmission include mucous membrane contact, accidental inoculation, and contact with infected body fluids. Person-to-person transmission has occurred from bite wounds. Infection can occur after surgery, trauma, anoxia, tissue destruction, and animal bites.3 The incubation period hasn't been conclusively determined. This organism can also be found in mud, water, and decaying animal carcasses.4 Horses, cattle, sheep, goats, pigs, and fowl may also host this organism.3

Within the genus Fusobacterium are other pathogenic species, including F. nucleatum, F. canifelinum, and F. gonidiaformans. F. necrophorum is the most virulent species.3

Fusobacterium infections occur worldwide but are infrequent, with one study identifying 5.5 cases per 1 million people per year.5 Infection with this organism isn't nationally reportable to the CDC.6

Even though it's commonly considered part of the normal flora in some areas of the body, Fusobacterium should always be treated as a pathogen because it can cause various infections. For example, fusobacterium can be responsible for periodontal disease, jugular vein suppurative thrombophlebitis, skin ulcers, intraabdominal abscesses, neck space infections, polymicrobial infections, and peritonsillar abscesses. Fusobacterium has also recently been associated with ulcerative colitis.7

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Possible role in carcinogenesis

The pathogenicity of Fusobacterium isn't well-known, and the role of this microbe and its function in carcinogenesis is very poorly understood. However, a different type of species of Fusobacterium, F. nucleatum cells have been found in colon cancer cells.7 In 2011, researchers found that colorectal carcinomas were filled with F. nucleatum.7 Despite the apparent link between this microbe and colon cancer, F. nucleatum's role in carcinogenesis is still unclear.

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One major factor in the treatment of an infection with Fusobacterium depends on where the infection occurs in the body.

Fusobacteria are known to have a high resistance to macrolides, and penicillin may not be effective.3 (See Antibiotic therapy for Fusobacterium for recommended drugs and drug combinations.) In some cases, surgical drainage of an abscess is indicated. No vaccine is currently available to prevent Fusobacterium infections.

Use standard precautions when caring for patients with Fusobacterium infections.8 Teach patients with the infection to complete the prescribed course of antibiotic therapy and to promptly report potential adverse drug reactions and worsening signs and symptoms to their healthcare provider.

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Looking ahead

It's important for nurses to recognize patients who may be at risk for a Fusobacterium infection. As illustrated in the case study, even a noninvasive, routine procedure such as a dental cleaning can turn a microbe that's part of normal human flora into an organ system infection.1 As we learn more about the bacterium, the next challenge is to elucidate how this microorganism influences carcinogenesis.

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The following antibiotics can be used to treat Fusobacterium:3

  • metronidazole
  • piperacillin/tazobactam
  • ticarcillin/clavulanate
  • amoxicillin/sulbactam
  • ampicillin/sulbactam
  • ertapenem
  • imipenem
  • meropenem
  • clindamycin
  • cefoxitin
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1. Bytyci F, Khromenko E. Hepatic abscess caused by Fusobacterium necrophorum after a trip to the dentist. BMJ Case Rep. 2016.
2. The University of Alabama. Bacteria shapes and arrangement.
3. Public Health Agency of Canada. Fusobacterium spp. 2011.
4. Brooks K. Ready Reference for Microbes. 3rd ed. Washington, DC: APIC; 2012.
5. Afra K, Laupland K, Leal J, Lloyd T, Gregson D. Incidence, risk factors, and outcomes of Fusobacterium species bacteremia. BMC Infect Dis. 2013;13:264.
6. Centers for Disease Control and Prevention. 2017 Nationally notifiable conditions. 2017.
7. Castellarin M, Warren RL, Freeman JD, et al Fusobacterium nucleatum infection is prevalent in human colorectal carcinoma. Genome Res. 2012;22(2):299–306.
8. The Centers for Disease Control and Prevention. Isolation guidelines.
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