Prevention of Surgical Site Contamination With Cutibacterium acnes During Cardiac Surgery: A Randomized Clinical Trial.

Importance: Cutibacterium acnes, traditionally considered a contaminant, is increasingly recognized as a relevant pathogen of prosthetic valve endocarditis, particularly in men. It is hypothesized that intraoperative transfer from incised hair follicles at the sternal wound margin occurs despite current standard disinfection protocols. Objective: To evaluate whether additional intraoperative hygiene measures reduce surgical site contamination with C acnes during cardiac surgery. Design, Setting, and Participants: This multicenter, parallel-group, blinded randomized clinical trial was conducted from October 28, 2024, to March 3, 2025, at 1 university hospital and 1 university-affiliated teaching hospital in Munich, Germany. Participants were male patients undergoing first-time cardiac surgery. Patients and laboratory personnel were blinded to group assignments. The analysis was based on a per-protocol design. Six patients were excluded after randomization due to incorrect sampling (n = 4) or incorrectly performed intervention procedures (n = 2). Intervention: The intervention group received additional hygiene measures after sternotomy, including changing outer gloves, disinfecting sternal wound margins with iodine, and covering them with sterile absorption pads. The control group received usual care, which included a glove change after sternotomy without additional skin margin treatment. Main Outcomes and Measures: The primary outcome was perioperative C acnes contamination, measured by the number of culture-positive swabs, amount of growth on agar, and pathogen identification via matrix-assisted laser desorption-ionization time of flight mass spectrometry. Results: Among 124 male patients (mean [SD] age, 68.5 [9.9] years) included in the analysis, C acnes was detected significantly less frequently in the intervention group (9 of 62 [14.5%]) compared with the control group (38 of 62 [61.3%]; risk ratio [RR], 0.24 [95% CI, 0.13-0.45]; P < .001), representing a relative risk reduction of 76%. Regarding growth intensity in the pericardium, the intervention group showed 100% negative or thioglycolate-only growth, whereas 27 patients (43.5%) in the control group exhibited agar growth (1+ to 3+). Overall bacterial contamination was similarly reduced (10 of 62 [16.1%] vs 44 of 62 [71.0%]; RR, 0.23 [95% CI, 0.13-0.41]; P < .001). Chest hair density was identified as a risk factor for contamination (odds ratio, 1.16 [95% CI, 1.02-1.31]; P = .02). Conclusions and Relevance: In this randomized clinical trial of 124 male patients undergoing cardiac surgery, additional intraoperative hygiene measures targeting the wound margin significantly reduced C acnes transfer to the surgical site. These simple, low-cost strategies should be considered for implementation in standard surgical protocols to potentially prevent prosthetic valve endocarditis. Trial Registration: German Clinical Trials Register: DRKS00035169.