Neisseria sicca Vertebral Osteomyelitis: A Case Report and Literature Review

<b>Background</b>: Culture-negative vertebral osteomyelitis presents a significant diagnostic challenge. <i>Neisseria sicca</i> (<i>N. sicca</i>) is a typically benign commensal organism of the upper respiratory tract that rarely causes invasive infections, warranting cautious interpretation if isolated in a single positive culture. This case study details a 62-year-old male diagnosed with vertebral osteomyelitis caused by <i>N. sicca</i>, examining diagnostic challenges, treatment, and outcomes. <b>Methods</b>: We conducted a comprehensive search on MEDLINE using the keywords "<i>Neisseria sicca</i>", "osteomyelitis", and "diskitis". An additional search excluding <i>N. gonorrhea</i> and <i>N. meningitidis</i> was also performed, revealing a total of four cases of <i>N. sicca</i> osteomyelitis in the literature. <b>Results</b>: A 62-year-old male with a history of hypertension, type 2 diabetes, atrial fibrillation, and previous L5-S1 spinal fusion presented with fever and back pain in May 2023. Initial imaging revealed T8-T9 vertebral osteomyelitis. Despite a six-week course of IV daptomycin, his symptoms worsened, prompting further evaluation. A CT-guided biopsy with comprehensive testing, including histopathology and microbial cultures, initially identified <i>N. sicca</i>. Due to its rarity, additional biopsies were conducted, confirming the infection. IV ceftriaxone was initiated, leading to significant pain improvement, and a subsequent MRI showed near resolution. The patient transitioned to oral cefuroxime, with follow-up confirming complete infection resolution by December 2023. <b>Conclusions</b>: This case underscores the importance of a structured diagnostic approach in culture-negative vertebral osteomyelitis to differentiate between commensal contamination and true infection. Repeated positive cultures of <i>N. sicca</i> from a sterile site confirmed its role as the causative agent. Early identification and targeted antibiotic therapy are critical to improving outcomes in rare cases of <i>N. sicca</i> vertebral osteomyelitis.