(545) Infectious Outcomes Based on Antimicrobial Prophylaxis in Open Skull Fractures (SKULLCRACT Study)

Introduction: In patients with a traumatic brain injury, 17-28% have an associated skull fracture. Post-traumatic meningitis (PTM) increases risk of mortality by 10-15% and cost of hospitalization by approximately $10,000. The Infectious Disease Society of America (IDSA) guidelines recommended against prophylactic antimicrobials, given the 1.4% reported incidence of PTM in a 2015 Cochrane Review. Controversy surrounds this recommendation and IDSA endorses the need for further studies. The SKULLCRACT study was conducted to evaluate development of PTM despite antimicrobial prophylaxis.

Methods: SKULLCRACT is a multicenter, retrospective cohort study of adults (≥18yrs.) in the United States and Saudi Arabia admitted between June 1, 2015 - June 1, 2022. Patients were identified using ICD9/10 codes and trauma registry records and included if they presented with an open skull fracture. The primary outcome was PTM based on antimicrobial prophylaxis, and analyses utilized descriptive statistics, Chi-squared, or t-tests as appropriate.

Results: Eight institutions enrolled 304 patients, those with antimicrobial prophylaxis (PPX n=214) and those without (NOPPX n=90). Patients who received PPX were more likely to have a CSF leak (21% vs 10%, p=0.02), an extra ventricular drain placed (23.8% vs 2.2%, p < 0.0001), and a CSF culture obtained (18.7% vs 1.1%, p=0.000042). Cefazolin (36%) initiated within 24 hours of injury (93%) and continued for an average of 5 days (IQR 2-7) was the most common scenario. Of the patients who received PPX, 6 patients (2.8%) developed PTM, confirmed by a positive CSF culture. Of the patients who did not receive PPX, 0 developed PTM, 1 had a negative CSF culture and 0 patients required initiation of antimicrobials for concern of a CNS infection. Organisms isolated were Propionibacterium species (50%), Coagulase negative staphylococci (16.7%), ESBL K. pneuomoniae (16.7%), and MRSA concomitantly with C. perfringes (16.7%). Prophylactic regimens were equally too broad (30%), too narrow (30%), or appropriate (30%) based on culture results.

Conclusions: The SKULLCRACT study demonstrates a low risk of PTM and does not provide sufficient evidence for widespread utilization of broad-spectrum PPX in open skull fractures.