This study is about preventing surgical site infections of the shoulder. We hope to learn if clindamycin alone, benzoyl peroxide alone, or clindamycin and benzoyl peroxide together can affect growth of Propionibacterium acnes in the dermal layer.

P. acnes are skin pathogens known to cause surgical site infections despite proper preoperative surgical preparation. Lee et al. showed 70% growth rate of P. acnes despite the application of Choraprep prior to sampling. However, this study was limited as it failed to utilize a control group and only investigated one preparatory technique. Meanwhile, there remains to date no study investigating the effect of topical treatments. The purpose of this study is to investigate how specific topical treatments affect growth in the dermal layer. 12 volunteers who are normal volunteers, students, or employees of USC will each receive 4 punch biopsies from their back above the scapular spine, with each biopsy taken from a region of the skin treated with a different topical (topical clindamycin alone, topical benzoyl peroxide alone, topical clindamycin and benzoyl peroxide together, and a control). A 3df overall test of the treatment indicators will test for any differences in positivity for P Acnes among the treatments; pairwise comparisons among the treatments will adjust for multiple comparisons. A two-tailed statistical test will be performed, testing at an alpha of 0.05, and analyses will also be performed based on hemolytic subtypes.

Inclusion Criteria:

• healthy volunteer
• age > 18

Exclusion Criteria:

• history of antibiotic use in the last month
• active acne on the back
• non-English speakers (the study personnel do not have adequate training to converse and consent in other languages)

Yes Data will be shared as required with the USC Health Sciences Institutional Review Board. Participant data will be coded with coding identifiers kept separately by research personnel only and destroyed upon completion of the study.

24 days