Wound Margin Coverage Lowers Cutibacterium Acnes Contamination

Key Takeaways

• The added wound-margin disinfection and pad coverage was associated with lower perioperative C acnes contamination than usual care.
• Any bacterial contamination was also less frequent with the intervention at 16.1% compared with 71.0% in controls.

In a multicenter randomized clinical trial of men undergoing first-time cardiac surgery, post-sternotomy iodine disinfection of the sternal wound margins plus sterile absorption-pad coverage was associated with less intraoperative C acnes contamination than usual care with glove change alone. C acnes contamination occurred in 14.5% of the intervention group and 61.3% of controls, with a risk ratio of 0.24.

The investigator-initiated, multicenter, parallel-group randomized trial was conducted at a university hospital and a university-affiliated teaching hospital in Munich, Germany, from October 28, 2024, to March 3, 2025. A power calculation indicated that 122 participants were needed, and 130 were enrolled to allow for dropouts. Six patients were excluded after randomization because of incorrect sampling or incorrectly performed intervention procedures, leaving 124 patients for per-protocol analysis, with 62 patients in each group. Patients and laboratory personnel were blinded, although the intraoperative team collecting samples was not. Coronary artery bypass grafting was the most common procedure. After sternotomy, both groups had an outer glove change, and only the intervention group also received iodine disinfection and sterile pads beneath the rib retractor.

Perioperative C acnes contamination was defined by culture-positive swabs, semiquantitative agar growth, and species identification with MALDI-TOF mass spectrometry. Baseline swabs were obtained immediately after sternotomy from the wound margins and the surgeon's gloves. Outcome swabs were collected near the end of surgery, before cannula removal and pericardial closure, including pericardium and glove samples. Swabs traveled in liquid Amies medium, then underwent culture on blood agar and in thioglycolate broth with anaerobic incubation at 37 C for 10 days; baseline prevalence was high on wound and glove swabs immediately after sternotomy.

In the per-protocol analysis, the primary outcome favored the intervention, with a 95% CI of 0.13 to 0.45 and P < .001 for the reported risk ratio. Lower contamination was also seen across the operative pericardial and glove sampling sites. Overall bacterial contamination showed a similarly wide separation between groups. Chest hair density was associated with C acnes-positive skin swab results, with an odds ratio of 1.16 per 1 cm2, a 95% CI of 1.02 to 1.31, and P = .02.

The intervention was described as practical and easy to integrate into standard workflow. No adverse effects related to the intervention were observed. The enrolled cohort included only men, limiting generalizability.