Lumbar postoperative Aspergillus flavus infection after lumbar spondylolisthesis fusion: a case report and literature review.

Surgical site infection following lumbar internal fixation and fusion is predominantly bacterial. Aflatoxin-associated discitis is extremely rare in immunocompetent patients and often results in delayed diagnosis and inadequate empirical antimicrobial treatment. This report presents a 74-year-old immunocompetent male patient who underwent elective posterior lumbar interbody fusion for grade II degenerative lumbar spondylolisthesis and developed intractable low back pain 3 months postoperatively. Despite multiple courses of broad-spectrum antibiotic therapy administered at two external hospitals, his symptoms did not resolve. Conventional bacterial, mycobacterial, and fungal cultures, as well as histopathological examination of percutaneous biopsy and intraoperative specimens, yielded negative microbial results. Metagenomic next-generation sequencing (mNGS) specifically identified Aspergillus flavus in all tissue samples, confirming the etiological diagnosis of fungal discitis. The patient received staged combined antifungal and surgical management. Intravenous voriconazole was used for induction therapy, followed by radical debridement of infected spinal tissue, internal fixation revision, and bone graft reconstruction. Oral voriconazole was prescribed for 3 months of postoperative maintenance therapy. A 12-month follow-up showed marked pain relief, and serial imaging and laboratory tests confirmed complete eradication of the infection with no recurrence. This case is systematically compared with previously reported Aspergillus spinal infections in immunocompetent hosts. mNGS serves as a valuable adjunctive diagnostic tool for clinically suspected atypical infections when conventional examinations are negative. Although limited by a single-case, single-center design without statistical generalizability, this report expands clinical recognition of post-fusion fungal discitis in immunocompetent patients and provides practical evidence for precise diagnosis and individualized management of refractory spinal surgical site infections.