Gram-Negative Organisms Implicated in 31.5% of Spinal Fusion Surgical Site Infections

Researchers analyzed postoperative spinal fusion surgical site infections reported voluntarily to the CDC National Healthcare Safety Network during 2021–2022. The cross-sectional study included 7,187 cases after excluding infections present at surgery. It characterized microbial etiology and assessed factors associated with gram-negative infection relative to monomicrobial Staphylococcus aureus infection.

Gram-negative bacteria were implicated in 2,265 cases (31.5%), including mixed infections. Escherichia coli occurred in 565 cases (7.9%) and Pseudomonas aeruginosa in 501 (7.0%). S. aureus was the most common individual pathogen, identified in 2,200 cases (30.6%). Overall, 61.3% of infections were monomicrobial, 17.6% polymicrobial, and 21.1% culture-negative. Median time to infection diagnosis was 21 days.

Older age, female sex, higher body mass index, longer operations, higher American Society of Anesthesiologists class, lumbar involvement, inpatient surgery, and emergency or trauma surgery were independently associated with gram-negative etiology. Female sex was associated with an odds ratio of 1.39 (95% CI 1.19–1.59) versus monomicrobial S. aureus infection.

These profiles may help guide empiric gram-negative coverage when treating established infections. They do not establish that broader prophylaxis improves outcomes; the authors propose that question for future studies. Voluntary reporting and the observational design limit interpretation, and the analysis describes etiology among infection cases rather than infection risk across all spinal fusions. The journal article is an early-release version subject to change.