Metagenomic Next-Generation Sequencing in Brucellar Spondylitis with Discordant Serologic Findings in a Non-Endemic Region: A Case Report and Literature Review.

BACKGROUND: Brucellar spondylitis (BS) is a focal osteoarticular manifestation of brucellosis with nonspecific clinical and imaging features. Diagnosis may be difficult in areas where brucellosis is not traditionally considered endemic, particularly when epidemiologic exposure is not identified and serologic tests yield discordant results. We report a case in which metagenomic next-generation sequencing (mNGS) of vertebral lesion tissue provided additional microbiologic evidence for the diagnosis.

CASE PRESENTATION: A 71-year-old man presented with a 2-month history of fatigue, anorexia, night sweats, and worsening back pain without an identifiable epidemiologic exposure. Imaging showed destructive T8-T9 spondylitis with intervertebral disc involvement, paravertebral soft-tissue swelling, and small abscess formation. CT-guided biopsy demonstrated inflammatory changes, while routine bacterial culture, lesion-based MTBC DNA/RNA testing, and mycobacterial culture were negative. Brucella-specific immunoglobulin G (IgG) and immunoglobulin M (IgM) antibodies were positive, whereas the standard tube agglutination test (SAT) titer was <1:25 and the Rose Bengal test (RBT) was negative. mNGS of vertebral lesion tissue detected Brucella spp. DNA. Serial serologic testing subsequently showed SAT titers of 1:200 and 1:400, with later conversion of the RBT to positive, providing further support for brucellar spondylitis. The patient received combination anti-brucellar therapy and underwent posterior thoracic fixation, spinal canal decompression, lesion debridement, and bone graft fusion because of extensive vertebral destruction and concern for spinal instability. At approximately 10 weeks after treatment initiation, while anti-brucellar therapy was ongoing, back pain had markedly improved.

LITERATURE REVIEW: Published studies suggest that mNGS may improve pathogen detection in selected spinal infections when conventional microbiologic testing is unrevealing. Reports of focal brucellosis also show that lesion-derived specimens may provide microbiologic evidence that complements peripheral serologic findings.

CONCLUSION: In this case, mNGS did not identify a previously unsuspected pathogen but added microbiologic evidence from the affected vertebral lesion to an otherwise discordant serologic profile. Tissue-based mNGS may be useful in selected patients with suspected BS when conventional serologic findings are discordant and culture is negative.