CT-guided biopsy in suspected spondylodiscitis: microbiological yield, impact on antimicrobial treatment, and relationship with outcome.

Purpose: To investigate the clinical impact of CT-guided biopsy, as performed in routine clinical practice, in patients with suspected spondylodiscitis on MRI in terms of culture yield, impact on antimicrobial treatment, and outcome.
Methods: This study included 64 patients with MRI findings compatible with spondylodiscitis who underwent CT-guided biopsy.
Results: Initial CT-guided biopsies were culture-positive in 20/64 (31.3%, 95% confidence interval [CI] 21.2-43.3%). Repeat CT-guided biopsies (after initial negative biopsy) were culture-positive in an additional 5/15 (33.3%, 95% CI 15.2-58.3%). Serum leukocytes, C-reactive protein, pre-biopsy use of antibiotics, neurological symptoms, MRI findings, vertebral height loss, and hyperkyphosis were not significantly different between culture-positive and culture-negative cases (P = 0.214-1.000); 75% (15/20) of initial CT-guided biopsies that were culture-positive provided additional information to clinicians for guiding antibiotic treatment. Sixty-two of 64 patients (96.9%, 95% CI 89.3-99.1%) would have been adequately treated if a strategy was followed that would subject all patients without clinical findings suspicious for "atypical" microorganisms and negative blood cultures to empirical antibiotics (i.e., clindamycin for coverage of Gram-positive bacteria) without using biopsy results to determine the optimal antibiotic regimen. Outcome within 6 months (development of neurologic or orthopedic complications, surgery, and death) was not significantly different (P = 0.751) between culture-positive and culture-negative patients.
Conclusions: Although CT-guided biopsies are culture-positive in a minority of cases, the majority of positive cultures are useful to tailor antibiotic treatment. Empirical treatment with clindamycin may cover almost all micro-organisms in positive biopsy specimens, provided patients are not immunocompromised. Outcome appears similar between culture-positive and culture-negative patients.