In prior studies these authors demonstrated the broad spectrum, in vitro antimicrobial efficacy of protocatechuic acid (PCA), a phytochemical found in food plants.
In this study they investigated the antimicrobial efficacy of protocatechuic acid (PCA) as a topical reagent for surgical skin antisepsis over the shoulder joints of health volunteers randomized to topical treatment with PCA (a 10% concentration of PCA in Phase I [11 subjects] and a 17% concentration in Phase II [12 subjects]), with a control of isopropyl alcohol (IPA) applied to the contralateral shoulder. Six male and 5 female subjects participated in Phase I, and 8 male and 4 female subjects participated in Phase II.
Mechanical scraping was performed for skin harvest following reagent application, and samples were sent for aerobic and anaerobic culture for Cutibacterium. Twenty minutes following treatment, the back of a sterile scalpel was rubbed with moderate pressure over the demarcated skin surface to maximize the harvesting of microbes on, and deep to, the surface of the skin and a second swab was used to sample the harvested skin layers and appendages.
The topical application of 10% PCA was associated with significantly higher aerobic and anaerobic sterilization rates (90.9% and 81.8%, respectively) compared with treatment with IPA (p = 0.0143 and p = 0.0253, respectively).
The topical application of 17% PCA was associated with a significantly higher anaerobic sterilization rate (83.3%) and trended toward a significantly higher aerobic sterilization rate (91.7%) compared with treatment with IPA (p = 0.0143 and p =0.083, respectively).
In Phase I, Cutibacterium were identified in 2 (18.2%) of 11 subjects following topical application of 10% PCA. Both of these subjects had >200 anaerobic CFUs prior to treatment, with prominent colonies of C. acnes identified. Following treatment, 1 CFU of C. acnes was grown on culture for each of these subjects.
In Phase II, 0 (0%) of 12 subjects were positive for C. acnes following topical application of 17% PCA. Prior to treatment, prominent colonies of C. acnes were identified in 3 of the 4 shoulders of subjects for whom Phase-II DNA analysis was performed. Staphylococcus epidermidis was the only organism identified for subjects with positive anaerobic culture results following treatment with 17% PCA.
Comment: This is an interesting study of PCA. The method of sampling by scraping the skin surface likely to only harvest organisms in the superficial layers of the skin in contrast to studies where the full thickness of the freshly incised dermis is sampled.
Thus it is difficult to know whether or not the effect of PCA extends to the pilosebaceous units. The sampling was carried out 20 minutes after application, so it is unclear how long the antibacterial effect lasts (note that in a shoulder arthroplasty the skin remains open with the incised pilosebaceous units exposed for 1-2 hours). The authors did not compare the results of male and female subjects: males have been shown to be at much greater risk for Cutibacterium periprosthetic infection.
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