ANTIMICROBIAL PROPHYLAXIS FOR SKIN COLONIZATION WITH CUTIBACTERIUM ACNES IN PRIMARY OPEN SHOULDER SURGERY: A DOUBLE-BLINDED RANDOMIZED CONTROLLED TRIAL PRELIMINARY RESULTS

In shoulder surgery, most surgical site infections (SSI) are caused by Cutibacterium acnes (C. acnes) rather than staphylococcus. Recommended antibioprophylaxis in current literature, i.e. first-generation cephalosporins, is being questioned as it does not provide optimal coverage against cutibacterium. Antibiotics generating the lowest minimum inhibitory concentration (MIC) against C. acnes are Penicillin G, ceftriaxone and Clindamycine. Due to antibiotic resistance issues and serious adverse side effects, Penicilin G and Clindamycin have not been recommended as antibioprophylaxis. Ceftriaxone appears to be an appealing alternative to prevent shoulder infections as it covers cutibacterium in addition to a majority of microorganisms found on the skin flora. The purpose of this study was to determine whether ceftriaxone is superior to cefazolin to decrease skin colonization in open shoulder surgeries by quantifying the organisms identified in surgical site biopsies pre op and post op. Participants and surgeons were double blinded and randomized by block (gender and surgery type) to be given either Cefazolin or Ceftriaxone. On the day of the surgery, two skin biopsies were taken with a reproducible technique, one at time of incision and one at closure. Samples were sent for incubation. Anaerobic incubation was prolonged to up to 14 days in order to identify C. acnes. Surgeons and OR care team, microbiology laboratory team and research assistants were blinded to the randomization, until the end of data collection. From 2016 to 2024, 72 open shoulder procedures (32 males, 40 females, mean age 64.62) were performed: 43 elective and 28 trauma surgeries. Thirty-nine patients received cefazolin and 32 patients received ceftriaxone. One patient was excluded because she was allergic to penicillin and one because his surgery was over the week-end. The positive culture rate at initial biopsy was 31% for the group receiving cefazolin, and 38% for the group receiving ceftriaxone (OR 1.35 (0.5–3.62), p=0.731). At wound closure, the positive culture rate for any microorganism was 31% for the group receiving cefazolin, and 50% for the group receiving ceftriaxone (OR 2.25 (0.85–5.94), p=0.16). At initial biopsy, the positive culture rate for C. acnes was 21% for the cefazolin group and 19% for the ceftriaxone group (OR 0.89 (0.27–2.91), p=> 0.999). One patient was diagnosed with a C. acnes deep SSI 6 months after her primary elective total shoulder arthroplasty. She was treated with intravenous antibiotics and underwent a two-stage procedure. Antibiotic selection did not show a significant difference in colonization rates at the beginning and end of surgery, regardless of recent studies suggesting greater antibiotic coverage with ceftriaxone. This implies that ceftriaxone is not more effective than cefazoline in preventing skin colonization during shoulder surgery.