Vertebral osteomyelitis caused by Fusobacterium nucleatum with an associated asymptomatic liver abscess in an immunocompetent adult: A case report and literature review

Fusobacterium nucleatum rarely causes vertebral osteomyelitis or liver abscesses, and no reports exist of it concurrently causing vertebral osteomyelitis and pyogenic liver abscess. A 58-year-old woman with a history of periodontitis presented with worsening lumbago, left lower leg pain, numbness, and fever for a week. Physical examination indicated knocking pain at the L2-L3 levels with a psoas sign on the left side. A magnetic resonance image showed L2-S1 vertebral osteomyelitis and intervertebral discitis, with a left psoas major muscle abscess. Vertebral osteomyelitis caused by Staphylococcus aureus was suspected; blood cultures were obtained, and intravenous cefazolin was administered. Computed tomography, which was performed to detect disseminated foci, revealed a multilocular liver abscess. On day 4 of incubation, the anaerobic blood culture bottles were positive for characteristic filamentous gram-negative rods. The empiric antimicrobial therapy was changed to ampicillin/sulbactam. The isolate was identified as F. nucleatum based on 16S rRNA gene sequencing. The liver abscess was drained on day 12. Based on the antimicrobial susceptibility test results, the patient was treated with intravenous ampicillin/sulbactam for 4 weeks followed by oral amoxicillin/clavulanate for an additional 8 weeks and remained disease-free at the 1-year follow-up. Clinicians should consider F. nucleatum as the causative organism for vertebral osteomyelitis presenting with asymptomatic pyogenic liver abscess. The gold standard for identifying and diagnosing F. nucleatum infections is 16S rRNA gene sequencing, and gram staining helps determine appropriate antimicrobials.