These authors point out that most of the surgical site infections after shoulder surgery are caused by Cutibacterium. Topically applied benzoyl peroxide (BPO) has for years been used to decrease the skin load of Cutibacterium in treatment of acne vulgaris. They examined this effect on bacterial colonization in patients subjected to elective shoulder surgery at different stages of the procedure in 100 patients scheduled for primary elective open shoulder surgery. Patients were randomized to preoperative skin preparation either with BPO or with soap (control group).
All patients were instructed to shower and wash with regular soap the night before and in the morning of the day of surgery. The BPO group were instructed as follows: in the morning and evening two days prior to surgery a 5 cm strip of 5% BPO gel was applied to the shoulder on dry skin and rubbed in. The procedure was repeated next day and a fifth and final application was made in the morning on the day of surgery. The last two applications were made after showering.
Four skin swabs were taken in a standardized manner at different times, before and after surgical skin preparation, one in dermis, and finally after the skin was sutured. Before skin incision five punch biopsies (3 mm in diameter and maximum 4 mm deep) were obtained spaced 2 cm apart in the planned skin incision.
Dermal skin swabs showed bacterial growth in 31/100 participants. There was mixed bacterial flora in 3/31: two with S. saprophyticus and in one S. epidermidis. In the remaining 28/31 there was growth solely of Cutibacterium– 17/55 in the control group and 11/45 in the BPO group. Only 12 of these had bacterial growth when culturing the biopsies. Bacterial counts in the dermis showed no difference between the groups.
23/100 patients had bacterial growth in the biopsies, 15 men and 2 women in the control group (n=55) and 6 men and no woman in the BPO group (n=45). Out of these 23, there was Staphylococci growth in five (4/5 control group, 1/5 BPO group). Remaining 18/23 had Cutibacterium but not in all biopsies. There was no significant difference between the groups when requiring three out of five as a positive culture.
Comment: This is a well done, controlled study. It is of interest that BPO appeared to have an effect on the skin surface swabs, but not on the dermal samples (swabs or punch biopsies). 12 of subjects with the culture negative swabs after skin preparation still had viable bacteria in the dermal cultures. Thus despite preoperative skin preparation, viable Cutibacterium persisted in the dermal layer.
It seems likely that these living bacteria in the dermal layer are released into the surgical field when the surgeon cuts through the skin
The reader interested in the value of benzoyl peroxide skin treatment will want to read these six posts:
link1, link2, link3, link4, link5, link 6
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