Fusobacterial Pyogenic Arthritis in Two School-Aged Children

Pyogenic arthritis can occur after hematogenous inoculation, direct extension from adjoining structures, or penetrating trauma. Staphylococcus aureus and group A streptococci are the major etiologic agents that cause septic arthritis in school-aged children. Reports of anaerobic bacteria causing such infections are exceedingly rare. We report two previously healthy children who developed pyogenic arthritis caused by Fusobacterium nucleatum.

Case Report

Patient 1.

A previously healthy 10-year-old Caucasian boy presented with left hip pain and a limp. Ten days before his admission, he developed upper respiratory infection symptoms without complaints of fever or sore throat. Two days before admission, he developed left hip pain and a limp. The hip pain gradually worsened, and on the day of admission, he became febrile and was unable to walk. There was no history of trauma or recent travel, and his immunizations were up to date. He presented to an outlying institution, where a bone scan revealed diffusely increased uptake in the left hip. He was then transferred to our institution. His examination revealed a fever to 39.80°C, tachycardia, with normal blood pressure and respiratory rate. He had exquisite tenderness, marked limitation, and internal rotation of the left hip and was not able to walk. The remainder of his examination, including the oral cavity and dentition, was unremarkable. He was taken to the operating room, where 15 cc of grossly purulent material was aspirated from the left hip joint. He then underwent open irrigation and debridement. The hip capsule was redundant and edematous, and a capsulotomy was made. The joint was irrigated copiously, and a drain was placed into the hip capsule. Gram stain on the purulent material revealed many polymorphonuclear cells but no organisms. Culture yielded F. nucleatum (beta-lactamase negative) after 5 days of incubation. Blood culture was negative. Admission laboratory results revealed a normal complete blood count and an erythrocyte sedimentation rate of 70 mm/h. The patient was treated initially with intravenous administration of oxacillin (150 mg/kg·day). Although there was clinical improvement postdebridement, he continued to have low-grade fever and hip pain for several days. After culture results became available, he was treated with intravenous administration of ticarcillin-clavulanate. He quickly became afebrile and regained full range of motion of his left hip over the next several days; he was discharged home on a treatment regimen of intravenous administrations of ticarcillin-clavulanate, with which he completed a 6-week course. He has remained well for 2 years after completion of his antimicrobial course.

Patient 2.

A previously healthy 8-year-old Caucasian boy presented with a 5-day history of right thigh, hip, and lower back pain. He was treated with analgesics but because of progressive pain and an inability to walk, he was referred to the orthopedic service at our children's hospital. There was no history of fever or recent upper respiratory symptoms, but he did manifest intermittent chills and night sweats in the days before admission. Two weeks before his presentation, he recalled having right hip and thigh pain associated with trauma (karate kick), which lasted 1 day and completely resolved. His immunizations were up to date, and there was no history of recent travel. Physical examination revealed an afebrile, diaphoretic child, a pulse of 120 beats per minute, a respiratory rate of 24/min, and blood pressure of 127/80 mmHg. He had exquisite tenderness over his right hip and right buttocks, decreased range of motion of his right hip and thigh, and he could not walk. Psoas and obturator signs were difficult to interpret because of his apprehension and diffuse tenderness. There were no obvious neurologic deficits. The remainder of his examination, including the oral cavity and dentition, was normal. Admission laboratory values revealed a normal complete blood count and an erythrocyte sedimentation rate of 52 mm/h. A bone scan revealed increased uptake in the right sacroiliac joint. A magnetic resonance imaging study revealed an area of enhancement in the right ileum and sacroiliac joint, without abscess or osteomyelitis. The patient underwent aspiration of the sacroiliac joint under fluoroscopic guidance. Cultures from three separate aspirations from the joint and surrounding areas revealed F. nucleatum (beta-lactamase negative) after 5 days of incubation. Gram staining of the material obtained from these aspirations, as well as blood cultures, failed to reveal an organism. The patient was treated empirically with intravenous administration of oxacillin. He continued to have right hip and thigh pain for several days after aspiration of his sacroiliac joint and refused to walk. When culture results became known, intravenous administration of ticarcillin-clavulanate was substituted for oxacillin. His symptoms improved gradually over the next several days, and he completed a 4-week course of intravenous administration of antibiotics at home. At the completion of his antibiotic course, he was walking without difficulty, had a normal erythrocyte sedimentation rate, and has remained well over the past 2 years.

Discussion

Fusobacteria are gram-negative, obligate anaerobic bacteria that are part of the normal flora of the oral cavity and gastrointestinal and female genital tracts. Pediatric infections that have been associated with these organisms include head, neck, and central nervous system infections, intra-abdominal infections, and septicemia. These organisms most commonly are isolated as part of polymicrobial infections and most commonly cause infections in adolescents and young adults [¹]. Because these are anaerobic organisms, their recovery in the laboratory depend on collection, transportation, and incubation in appropriate anaerobic environments.

Fusobacterial bone and joint infections in children usually are the result of direct extension from a contiguous focus of infection such as mastoiditis and sinusitis or are part of the metastatic complications of bacteremia [^2,3]. Brook [¹] described eight cases of osteomyelitis from which Fusobacterium species were recovered, but in only one of these cases were these organisms isolated alone. All eight cases described a contiguous focus of infection (mastoiditis, sinusitis, soft-tissue infection). Rathore et al. [²] reported two patients with blood and joint infections caused by F. necrophorum who had unusually prolonged clinical courses despite aggressive antimicrobial and surgical intervention. Beauchamp and Cimolai [⁴] reported a 6-year-old boy who developed osteomyelitis of the ileum caused by F. nucleatum. Reports of fusobacterial bone and joint infections in adults likewise are rare [^5,6].

F. nucleatum was one of several anaerobic species recovered in culture in 1898 (in one of the earliest descriptions of human anaerobic infections) and is currently the Fusobacterium species most frequently encountered in clinical infections. It has been associated with oral infections such as tonsillitis, peritonsillar abscess, and dental infections, as well as lung infections, including aspiration pneumonia and lung abscess. Although F. necrophorum is associated with Lemierre syndrome, which is characterized by postanginal sepsis, septic thrombophlebitis of the internal jugular vein, and distant metastatic abscesses, F. nucleatum has only very rarely been associated with this syndrome [⁷]. Unlike other Fusobacterial species, F. nucleatum appears as a slender rod with tapering, pointed (rather than round) ends on gram staining.

The pathophysiology of septic arthritis in our patients is unclear. Neither patient had bacteremia or evidence of Lemierre syndrome at the time of presentation. Patient 1 had a history of upper respiratory symptoms, which may have heralded a primary oropharyngeal infection. It is possible that these patients may have had a transient bacteremia after clinically silent pharyngitis, with metastasis to the joints. The history of trauma in patient 2 may have served as a nidus for infection. Alternatively, infection of the joint via direct extension from the gastrointestinal tract may have occurred, although there were no findings to implicate this route of infection and clinical follow-up has failed to reveal an underlying etiology.

The ability of fusobacteria, especially F. nucleatum, to produce beta-lactamase, has been clearly documented [⁸]. Although the organisms isolated in our patients did not elaborate beta-lactamase, there was a slow clinical response to surgical drainage and oxacillin therapy. Possible reasons for this slow response include: (1) the lack of intrinsic activity of oxacillin against gram-negative anaerobic organisms, despite the absence of betalactamase production; (2) fusobacteria may be more virulent than the organisms usually encountered with bone and joint infections. This unusual severity of illness has been reported with two cases of septic arthritis caused by F. necrophorum [²]; and (3) although fusobacteria were isolated in pure culture in our patients, these organisms may have been part of a polymicrobial infection. For any or all of these reasons, it seems reasonable that the addition of a more active and broad anaerobic antimicrobial agent would result in improved clinical response.

The two cases we report demonstrate that fusobacteria can cause joint infections without obvious evidence of a primary focus of infection in school-aged children. Thus, it is important that bone and joint specimens be collected and cultured anaerobically. Because these organisms may not be inherently susceptible to antimicrobial agents commonly used empirically for bone and joint infections and may elaborate beta-lactamases, they should be considered as etiologic agents in patients who do not have a good clinical response to appropriate surgical intervention and conventional antistaphylococcal therapy.