Antimicrobial Blue Light, Oregano Oil, and CZ Gel Manage Staphylococcus aureus Biofilms at the Skin-Implant Interface of Percutaneous Osseointegrated Prosthetics in an Ex Vivo Setup — MHSRS 2021

Ong J, Godfrey R, Peterson T, Tam J, Drake L, Navarian A, Epperson R, Isaacson B , Williams D

Abstract submitted to Military Health System Research Symposium 2021

Percutaneous osseointegrated prosthetics (POPs) are becoming available for those with limb loss as an alternative to prosthetic socket technology. POPs make it easier for amputees to attach and detach prostheses, and improve mechanical force feedback. Nevertheless, the percutaneous nature of POPs makes them susceptible to biofilm-related infection, with rates ranging as high as 30%; limiting a more widespread adoption. Infection causes skin irritation, discomfort, and may lead to deep infection if left uncontrolled. We hypothesized that antimicrobial blue light (aBL) can manage biofilm burden. However, while aBL disrupts bacterial membranes and kills cells, it may not completely eradicate biofilms as a standalone therapy. As a result, we explored the efficacy and potential synergy of oregano oil and CZ (anti-biofilm compound). Multi-day applications were tested against Staphylococcus aureus biofilms; common to POPs. These therapies may lead to more effective treatments for managing the S. aureus biofilm burden at the skin-implant interface of POPs. We built an ex vivo system using sterilized sheep skin (male/female) to simulate a POP environment translatable to an ovine model. S. aureus biofilms were grown on titanium (Ti) coupons in CDC biofilm reactors which were then used to inoculate the ex vivo skin-implant interface sites. For aBL treatment, inoculated skin samples were exposed twice daily to 405 nm aBL for 1 hour (900 J/cm2), with 6 hours between exposures; samples were covered and incubated when not treated. Oregano (10% w/v) and CZ (2% w/v) were formulated into gels. Each day, 1.5 mL of gel was aseptically applied to each sample. Samples were wrapped and incubated for 24 hours. All methods were tested at 1, 2, 3, 4, and 5-day intervals (n=8 per day). Bacteria were quantified using 10-fold dilution. Colony forming unit (CFU) counts were averaged and compared against a control set (skin inoculated with S. aureus, but not treated).