What is the clinical significance of Fusobacterium (a genus of bacteria)?

From the Guidelines

Fusobacterium is a genus of anaerobic, gram-negative bacteria that can cause serious infections, particularly in immunocompromised patients, and is associated with high morbidity and mortality rates, emphasizing the need for prompt and effective treatment. The clinical significance of Fusobacterium lies in its ability to cause a range of infections, including periodontal disease, pharyngitis, abscesses, and inflammatory bowel disease, as well as its link to adverse pregnancy outcomes and colorectal cancer 1.

Key Characteristics of Fusobacterium Infections

• Fusobacterium species, particularly F. nucleatum and F. necrophorum, are opportunistic pathogens that thrive in oxygen-poor environments, making deep tissue infections challenging to treat.
• These bacteria can cause serious infections when they spread beyond their normal habitats in the human oral cavity, gastrointestinal tract, and female genital tract.
• The bacteria's pathogenicity stems from its ability to adhere to host tissues, produce toxins, and evade immune responses.

Treatment of Fusobacterium Infections

• Clinicians typically prescribe antibiotics such as metronidazole (500mg three times daily for 7-14 days), clindamycin (300-450mg four times daily), or amoxicillin with clavulanic acid (875/125mg twice daily) to treat Fusobacterium infections.
• For severe infections, combination therapy or intravenous antibiotics may be necessary, highlighting the importance of prompt and effective treatment to reduce morbidity and mortality rates.
• The choice of antibiotic therapy should be guided by the severity of the infection, the patient's immune status, and the potential for antibiotic resistance, as noted in the guidelines for the diagnosis and management of skin and soft tissue infections 1.

Importance of Prompt Treatment

• The incidence of invasive candidiasis and other fungal infections can be reduced with prompt and effective treatment, emphasizing the need for aggressive systemic antifungal therapy in patients with suspected or confirmed fungal infections 1.
• The sensitivity of a single serum fungal antigen test is low, particularly in patients receiving antifungal agents, highlighting the importance of combining blood cultures, serial antigen detection, nucleic acid amplification techniques, radiographic imaging, and biopsy or aspiration of the abnormal skin or soft tissue lesion to increase the recovery of the offending pathogen and direct pathogen-specific antimicrobial therapy 1.

Clinical Manifestations and Diagnosis

• Dermatologic manifestations in patients with fever and neutropenia include erythematous maculopapular lesions, focal or progressive cellulitis, cutaneous nodules, and necrotizing fasciitis or myonecrosis, which can be caused by a range of pathogens, including Fusobacterium, highlighting the importance of prompt diagnosis and treatment 1.
• Ecthyma gangrenosum, a cutaneous vasculitis caused by invasion of the media and adventitia of the vessel wall by bacteria, can be a presenting feature of Fusobacterium infection, emphasizing the need for aggressive treatment and close monitoring of patients with suspected or confirmed infections.

From the FDA Drug Label

Metronidazole has been shown to be active against most isolates of the following bacteria both in vitro and clinical infections as described in the INDICATIONS AND USAGE section. Gram negative anaerobes: • Bacteroides fragilis group (B. fragilis, B distasonis, B. ovatus, B. thetaiotaomicron, B vulgatus) • Fusobacterium species

The clinical significance of Fusobacterium is that it is a gram-negative anaerobe that is susceptible to metronidazole, an antibiotic that is effective against most obligate anaerobes. This means that metronidazole can be used to treat infections caused by Fusobacterium. 2 3

From the Research

Clinical Significance of Fusobacterium Infections

The clinical significance of Fusobacterium infections can be understood by examining the various studies that have investigated the epidemiology, clinical outcomes, and treatment of these infections.

• Fusobacterium infections can lead to severe and life-threatening conditions, including Lemierre syndrome, septicemia, and bacteremia 4, 5.
• The bacteria can cause infections in various parts of the body, including the head and neck, soft tissues, and vertebral bodies 4, 6.
• Patients with Fusobacterium infections can be categorized into different groups based on the site of primary infection, with those having head and neck or soft tissue infections generally exhibiting more favorable outcomes than those with bacteremia 4.
• Surgical intervention coupled with antibiotic therapy is often the cornerstone of management for patients with head and neck or other soft tissue infections 4.
• The treatment of Fusobacterium infections typically involves the use of antibiotics, such as penicillin, cephalosporin, metronidazole, and clindamycin, and in some cases, surgical intervention may be required 4, 6, 5.
• Delayed treatment of Fusobacterium infections can lead to serious complications, including high mortality rates, particularly in patients with underlying comorbidities or those who are immunocompromised 4, 7.

Epidemiology and Outcomes

• The epidemiology of Fusobacterium infections has been studied in various settings, including tertiary care medical centers and district general hospitals 4, 7.
• The incidence of Fusobacterium species infections has been reported to be around 0.76 cases/100,000/year, with an overall death rate of 29% 7.
• The clinical spectrum of Fusobacterium infections can vary widely, ranging from mild to severe and life-threatening conditions, and the outcomes can depend on various factors, including the site of infection, underlying comorbidities, and timely treatment 4, 7.

Treatment and Management

• The treatment of Fusobacterium infections typically involves the use of antibiotics, and the choice of antibiotic can depend on the severity of the infection and the susceptibility of the bacteria 4, 6, 5.
• Surgical intervention may be required in some cases, particularly for patients with head and neck or other soft tissue infections 4, 6.
• Close monitoring and follow-up are essential for patients with Fusobacterium infections, particularly those who are immunocompromised or have underlying comorbidities 5, 7.