This case report presents a rare type I idiopathic necrotizing lower extremity infection from
Fusobacterium necrophorum: Gram-negative, obligate anaerobe, non-spore forming, pleomorphic bacillus [
8]. It has been isolated from the normal flora in the oral cavity, gastrointestinal tract, and genitourinary tract [
9]. When involved in disease and infection, necrotic lesions and deep abscess formation can occur, and bacteremia is not uncommon [
10].
Fusobacterium necrophorum is a well-established agent of disease above the diaphragm: it is commonly associated with Lemierre’s syndrome, a septic infection caused by thrombose formation within the jugular vein after colonization of a peritonsillar abscess [
11‐
13]. In recent epidemiological surveillance studies,
Fusobacterium has been determined to be the predominant organism causative of pharyngitis in a university clinic with 21% of the cases [
11]. Much more rarely though,
Fusobacterium necrophorum has been described as a potential causative agent of infections below the diaphragm. Beldman
et al. described a case of septic arthritis of the hip caused by
Fusobacterium necrophorum following a tonsillectomy [
14] and Patel
et al. also reported in an abstract a case of necrotizing fasciitis and pyomyositis in the thigh caused by
Fusobacterium necrophorum in a healthy adult [
15]. To the best of our knowledge, no other reports have been described directly linking
Fusobacterium necrophorum as the causative organism for necrotizing infections below the knee in the literature. Early diagnosis and treatment is critical due to the rapid extensive tissue destruction that ensues with these infections, and thus maintaining a high index of suspicion is vital for the survival of these patients. A high index of suspicion is required when choosing antibiotic coverage for necrotizing fasciitis and pyomyositis, and additional case reports of this occurrence may define a pattern of risk factors that should prompt
Fusobacterium coverage.
Our patient did not have any of the described risk factors for necrotizing fasciitis: diabetes mellitus, documented instances of recent and chronic intravenous drug abuse, age greater than 50, hypertension, and malnutrition/obesity [
16]. There were no obvious entrance wounds; thus, hematogenous spread of the infection from a possible pneumonic source or from oropharyngeal foci could not be ruled out, and has been described before [
17,
18].