Methods: We perform a retrospective study in one Swiss University Hospital (Geneva), and a prospective (confirmatory) trial in another one (Zurich) investigating the epidemiology and prevention of secondary SSI (Surgical Site Infections) under Open wound, revision surgeries and/or systemic antibiotic treatments. Specifically, we run a clinical trial randomizing (1:1) eligible adult orthopedic patients into a “standard” (cefuroxime) vs. a broad-spectrum prophylaxis (single-shot of combined vancomycin 1 g & gentamicin 5 mg/kg). In case of concomitant antibiotic therapies, the “standard” prophylaxis either represents cefuroxime or the continuation of the therapeutic agent.

Results: In Geneva, among 2480 episodes of orthopedic infections, we detected pathogens in 507 cases (507/862; 59%), of which 241 (242/507; 48%) were the same species found at the index debridement. In terms of new pathogens, there were 265 new SSIs (11% of the cohort) and in 174 cases (7% of cohort) these organisms were resistant to current antibiotic therapy. In Zurich, a total of 193 episodes received the “standard” prophylaxis and 147 the vancomycin-gentamicin combination. Among infected cases that were iteratively debrided, the proportion of secondary SSIs with new intraoperative pathogens was 17% in the standard vs. 10% in the broad-spectrum arm (χ2-test; p=0.03). As a consequence, the clinicians broadened the therapeutic antibiotic regimen in 17% of episodes with prior standard prophylaxis vs. 7% with previously broad prophylaxis (p=0.01). The association with immediate "clinical failures” in the aftermath of surgery was less in the broad-spectrum arm (71 failures / 193 standard prophylaxes vs. 44 failures / 147 broad-spectrum prophylaxis; p=0.18). When considering late failures, the corresponding proportions were 17% and 14%, respectively (p=0.91). The risk of Severe Adverse Events (SAE) during and after hospitalization was similar (41 in the standard vs. 35 in the broad-spectrum arm; p=0.57).

Conclusions: We saw a tendency to a better general SSI prevention in favor of the broad-spectrum prophylaxis, compared to the standard "protocol"; albeit not significantly. The benefit of the broad-spectrum prophylaxis seems higher for the prevention of future broader-spectrum antibiotic treatments.