Post-vertebroplasty lumbar spondylodiscitis due to Cutibacterium modestum.

Percutaneous vertebroplasty-associated spinal infection is uncommon but may cause progressive vertebral destruction and can mimic tuberculous spondylitis on imaging. The detection of low-virulence skin commensals such as Cutibacterium species in deep specimens also creates a diagnostic challenge because contamination and true infection must be distinguished. We report a 78-year-old man who developed recurrent progressive low back pain shortly after percutaneous vertebroplasty for an L2 compression fracture. Baseline computed tomography (CT) and contrast-enhanced magnetic resonance imaging (MRI) showed destructive spondylodiscitis centered at L2/3, with adjacent vertebral body and disc-space involvement, paravertebral inflammatory extension, and bilateral psoas abscess-like collections, initially suggesting tuberculous spondylitis. However, molecular testing for the Mycobacterium tuberculosis complex and targeted sequencing for mycobacterial drug-resistance genes were negative, and histopathology demonstrated acute and chronic inflammatory necrotic changes without typical tuberculous granulomas. Metagenomic next-generation sequencing of aspirated fluid identified a high abundance of Cutibacterium modestum, which was subsequently detected again in lesion tissue and peripheral blood by targeted high-throughput sequencing. Given the repeated detection in deep-site specimens, exclusion of tuberculosis and other competing diagnoses, compatible clinical and imaging findings, and improvement after targeted antimicrobial therapy and percutaneous stabilization, C. modestum was considered the most probable causative pathogen. These findings suggest that pathogen attribution in post-vertebroplasty spinal infection should rely on integrated clinical, microbiological, pathological, and therapeutic evidence rather than on imaging findings alone. Integrated clinico-microbiological assessment may improve pathogen attribution for rare low-virulence organisms in postoperative spinal infection.