Application of dermal chlorhexidine antisepsis is ineffective at reducing Proprionibacterium acnes colonization in shoulder surgery

Background: Chlorhexidine as a skin surface antiseptic has been shown to be ineffective with respect to reducing Proprionibacterium acnes colonization within the dermis. The purpose of the present study was to determine whether the application of aqueous chlorhexidine solution to the dermal layer decreased P. acnes colonization during open shoulder surgery. Methods: The present study enrolled 50 patients who were undergoing open shoulder surgery. Patients received standard antimicrobial preparation. Three dermal swabs were taken from each patient: swab 1 following skin incision; swab taken 2 minutes to 5 minutes post-application of aqueous chlorhexidine to the dermis; and swab 3 taken 60 minutes post-application. Results: Mean age was 57.5 years (22 males, 28 females). There were 21 patients (42%) with P. acnes present on any dermal swab. There were significantly more P. acnes positive cultures identified at swab 3 compared to swab 1 (p = 0.043). In nine patients with positive P. acnes at cultures swab 1, eight also isolated P. acnes after at swabs 2 or 3. Males were significantly more likely to have P. acnes on any swab (p < 0.001). Positive P. acnes cultures were significantly more common in patients ≤50 years (p <.001). None of the patients had any clinical signs of infection at a minimum of 1 year following surgery. Conclusions: Dermal application of aqueous chlorhexidine during open shoulder surgery fails to eradicate or reduce P. acnes on deep cultures.