Pyogenic Spondylodiscitis: Predictors of Microbiological Yield from Biopsy in a Tertiary Hospital.

Background and Objectives: Pyogenic spondylodiscitis (SD) is a severe spinal infection involving the intervertebral disc and adjacent vertebrae and is often associated with significant morbidity. Identifying the causative microorganism is crucial for targeted treatment; however, the microbiological yield from blood or tissue cultures varies widely due to factors such as prior antibiotic use and biopsy technique. In this study, we aimed to investigate the clinical, laboratory, and radiological predictors of microbiological yield, particularly from tissue biopsy specimens. Materials and Methods: This retrospective cohort study included adult patients diagnosed with pyogenic SD between January 2023 and July 2025 at a tertiary care hospital. Demographics, comorbidities, laboratory markers (CRP, ESR, ALP, albumin), radiological findings (abscess presence, anatomical location, claw sign), prior antibiotic use, and microbiological results were analyzed. Tissue specimens were obtained through either surgical sampling or needle biopsy. Univariable and multivariable logistic regression were performed to determine the predictors of positive tissue cultures. Results: Of the 159 patients screened, 55 met our inclusion criteria. The mean age was 63.9 ± 13.5 years, 80% had lumbar involvement, and 58.2% had abscesses, primarily paravertebral or psoas in location. Microorganisms were isolated in 65.5% of the cases, with Staphylococcus aureus being the most common (41.7%). The blood culture positivity was 55.5%, while tissue culture positivity was 40.4%. Logistic regression revealed that lower albumin (p = 0.046) and higher ALP levels (p = 0.045) were independent predictors of a positive microbial yield from tissue biopsies. Conclusions: Serum albumin and ALP levels may aid clinical decision-making regarding invasive sampling in SD. When blood cultures are negative and albumin is low while ALP is elevated, clinicians should consider prioritizing tissue biopsy. These findings may help optimize diagnostic strategies and should be validated in larger, prospective studies.