First Case of Fusobacterium necrophorum Endocarditis To Have Presented after the 2nd Decade of Life

Abstract

Fusobacterium necrophorum, an obligate, anaerobic, filamentous, gram-negative rod, is thought to be a normal inhabitant of the mucous membranes in human beings. Fusobacterium species have been implicated in cases of Lemierre syndrome and other pathologic conditions. Their reported association with infective endocarditis is extremely rare.

We describe the case of a previously healthy 34-year-old man who emergently presented with flu-like symptoms and dyspnea on exertion. He had recently undergone a dental procedure. Empiric antibiotic therapy was initiated. Blood cultures were positive for metronidazole-resistant F. necrophorum. A transesophageal echocardiogram revealed 2 mobile vegetations on the mitral valve. Despite the antibiotic therapy, the patient's respiratory status worsened and, after 3 weeks, he died. On the basis of the organism's pathophysiology and the patient's recent dental procedure, the oral cavity was the likely source of the bacteremia.

Our patient's case underscores the importance of recognizing Fusobacterium bacteremia as a possible cause of endocarditis. To our knowledge, this is the first reported case of monomicrobial F. necrophorum endocarditis to have presented in a patient after the 2nd decade of life. In addition, it is apparently only the 4th report of F. necrophorum mitral valve endocarditis with case results derived from modern culture techniques.

Fusobacterium necrophorum is an obligate, anaerobic, filamentous, gram-negative rod that frequently colonizes the human respiratory tract, gastrointestinal tract, and mouth. Fusobacterium species have been implicated in cases of Lemierre syndrome, meningitis, orbital cellulitis, necrotizing pneumonia, septic arthritis, and systemic infections.^1,2 We describe what appears to be the first reported case of monomicrobial F. necrophorum endocarditis in a patient 30 years of age or older. In addition, we list the documented cases of monomicrobial Fusobacterium endocarditis.

Case Report

A previously healthy 34-year-old man emergently presented with a one-week history of fever, chills, myalgias, abdominal pain, and dyspnea on exertion. He had been evaluated at a local clinic one week earlier for a presumed upper respiratory tract infection, and azithromycin had been prescribed. He had recently undergone an elective dental procedure. Despite the oral antibiotic therapy, his flu-like symptoms had progressed. Upon his admission to the emergency department, 4 blood cultures were obtained, and empiric therapy with intravenous vancomycin, ceftriaxone, and metronidazole was begun. After he was admitted to the hospital, all 4 blood cultures were reported to be positive for metronidazole-resistant F. necrophorum. The patient was continued on ceftriaxone therapy for gram-negative rod sepsis. Computed tomograms of his neck revealed an incidental parietal-lobe hypodensity without other acute pathologic indications. Subsequent images showed a subacute infarct involving the left occipital and parietal lobes. A transesophageal echocardiogram revealed 2 mobile vegetations on the mitral valve, and the diagnosis was F. necrophorum infective endocarditis.

The patient's fever and bacteremia persisted despite maximal antibiotic therapy, and his course was complicated by acute respiratory distress syndrome that necessitated intubation. His respiratory status worsened, and after 3 weeks, he died.

Discussion

Our review of the medical literature revealed 15 prior verifiable cases of monomicrobial Fusobacterium infective endocarditis (Table I).^1,4–17 To our knowledge, ours is the first documented case of F. necrophorum endocarditis to have presented after the 2nd decade of life.

TABLE I. Summary of Reported Cases of Fusobacterium Endocarditis

TABLE I, continued. Summary of Reported Cases of Fusobacterium Endocarditis

In reports of presumed gram-negative anaerobic endocarditis from before 1950 or so, the culprit organisms could not always be reliably identified. The chief reasons were inadequate microbiological detail and confusion pertaining to nomenclature.¹⁸ The comparatively unsophisticated anaerobic culture methods of earlier eras led to misattributed causation by streptococci and other organisms¹⁸; and, historically, F. necrophorum has probably been known by more than 50 names.¹⁹ Accordingly, ours is apparently only the 4th report of F. necrophorum endocarditis with case results derived from modern culture techniques.

Fusobacterium septicemia, a rare form of gram-negative sepsis, characteristically presents with high fever, pharyngitis, and submandibular adenopathy.² Fusobacterium necrophorum is classically associated with Lemierre syndrome (ipsilateral jugular vein thrombosis) after oropharyngeal trauma.² Very infrequently, the pathogen has been implicated in clinical cases of endocarditis. In a review of 48 cases of endocarditis caused by gram-negative anaerobic organisms (reported from 1940 through 1996), Bisharat and colleagues²⁰ determined that dental caries were implicated in 12 of the 35 cases in which an infection source was suggested. The results of our patient's physical examination and imaging studies were not consistent with an acute oropharyngeal pathologic condition. Nevertheless, on the basis of the known pathophysiology of the organism and the patient's recent dental procedure, it is reasonable to implicate the oral cavity as the source of the bacteremia.

Regardless of its source, Fusobacterium bacteremia is best treated by means of combination therapy consisting of a 3rd-generation cephalosporin and additional anaerobic coverage. In our patient, the unsuccessful response to therapy was attributed to an increased resistance to metronidazole. This case underscores the importance of recognizing Fusobacterium bacteremia as a possible cause of endocarditis after disruption of the oropharyngeal mucosa.