Surgical Site Infection After Craniotomy: Incidence, Microbiology, and Modifiable Risk Factors in a Retrospective Cohort of 350 Patients

Abstract

Background: Post-craniotomy surgical site infection (SSI) is a complication associated with neurological morbidity, repeat operations, and resource consumption. Reported risk factors are leakage of cerebrospinal fluid (CSF), long surgical procedure, drains or foreign objects, and use of antibiotics during the operation.

Objective: To determine the incidence and subtype distribution of 30-day SSI after craniotomy, the microbiology of this condition, and potentially alterable risk factors with special focus on antibiotic prophylaxis and perioperative factors.

Methods: This retrospective cohort study involved 350 adult craniotomy operations between 2022 and 2025. The primary outcome was 30-day SSI, and its subtypes were superficial incisional, deep incisional, or organ/space. Candidate predictors included diabetes, operative time, CSF leak, implants, CSF diversion drains, immunosuppressives or steroids, wound category, and timing and administration of perioperative antibiotic prophylaxis. Multivariable logistic regression estimated adjusted odds ratios (aOR) with 95% confidence intervals (CI).

Results: Thirty-day SSI occurred in 25/350 (7.1%) procedures; subtypes were organ/space 10 (40%), superficial 10 (40%), and deep 5 (20%). Cultures were positive in 21/25 (84%). The most common primary organisms were MSSA (5), coagulase-negative staphylococci (5), Cutibacterium acnes (4), culture-negative (4), Streptococcus spp. (3), Enterobacterales (3), and MRSA (1). No perioperative prophylactic antibiotics was associated with increased SSI odds (aOR 7.30; 95% CI 2.18–24.45; p=0.001).

Conclusions: In this cohort, 30-day SSI after craniotomy occurred in ~7%, with organ/space infections comprising 40%. The strongest modifiable association observed was absence of perioperative antibiotic prophylaxis.