An antimicrobial blue light device to manage infection at the skin-implant interface of percutaneous osseointegrated implants.

Antimicrobial blue light (aBL) is an attractive option for managing biofilm burden at the skin-implant interface of percutaneous osseointegrated (OI) implants. However, marketed aBL devices have both structural and optical limitations that prevent them from being used in an OI implant environment. They must be handheld, preventing even irradiation of the entire skin-implant interface, and the devices do not offer sufficient optical power outputs required to kill biofilms. We present the developmental process of a unique aBL device that overcomes these limitations. Four prototypes are detailed, each being a progressive improvement from the previous iteration as we move from proof-of-concept to in vivo application. Design features focused on a cooling system, LED orientation, modularity, and "sheep-proofing". The final prototype was tested in an in vivo OI implant sheep model, demonstrating that it was structurally and optically adequate to address biofilm burdens at the skin-implant of percutaneous OI implants. The device made it possible to test aBL in the unique OI implant environment and compare its efficacy to clinical antibiotics-data which had not before been achievable. It has provided insight into whether or not continued pursual of light therapy research for OI implants, and other percutaneous devices, is worthwhile. However, the device has drawbacks concerning the cooling system, complexity, and size if it is to be translated to human clinical trials. Overall, we successfully developed a device to test aBL therapy for patients with OI implants and helped progress understanding in the field of infection management strategies.

Comparison of Staphylococcus aureus tolerance between antimicrobial blue light, levofloxacin, and rifampin.

Background: Bacterial biofilms readily develop on all medical implants, including percutaneous osseointegrated (OI) implants. With the growing rate of antibiotic resistance, exploring alternative options for managing biofilm-related infections is necessary. Antimicrobial blue light (aBL) is a unique therapy that can potentially manage biofilm-related infections at the skin-implant interface of OI implants. Antibiotics are known to have antimicrobial efficacy disparities between the planktonic and biofilm bacterial phenotypes, but it is unknown if this characteristic also pertains to aBL. In response, we developed experiments to explore this aspect of aBL therapy. Methods: We determined minimum bactericidal concentrations (MBCs) and antibiofilm efficacies for aBL, levofloxacin, and rifampin against Staphylococcus aureus ATCC 6538 planktonic and biofilm bacteria. Using student t-tests (p < 0.05), we compared the efficacy profiles between the planktonic and biofilm states for the three independent treatments and a levofloxacin + rifampin combination. Additionally, we compared antimicrobial efficacy patterns for levofloxacin and aBL against biofilms as dosages increased. Results: aBL had the most significant efficacy disparity between the planktonic and biofilm phenotypes (a 2.5 log10 unit difference). However, further testing against biofilms revealed that aBL had a positive correlation between increasing efficacy and exposure time, while levofloxacin encountered a plateau. While aBL efficacy was affected the most by the biofilm phenotype, its antimicrobial efficacy did not reach a maximum. Discussion/conclusion: We determined that phenotype is an important characteristic to consider when determining aBL parameters for treating OI implant infections. Future research would benefit from expanding these findings against clinical S. aureus isolates and other bacterial strains, as well as the safety of long aBL exposures on human cells.

Antimicrobial blue light as a biofilm management therapy at the skin-implant interface in an ex vivo percutaneous osseointegrated implant model.

Biofilm contamination is often present at the skin-implant interface of transfemoral osseointegrated implants leading to frequent infection, irritation, and discomfort. New biofilm management regimens are needed as the current standard of washing the site with soap and water is inadequate to manage infection rates. We investigated the potential of antimicrobial blue light, which has reduced risk of resistance development and broad antimicrobial mechanisms. Our lab developed an antimicrobial blue light (aBL) device uniquely designed for an ex vivo system based on an established ovine osseointegrated (OI) implant model with Staphylococcus aureus ATCC 6538 biofilms as initial inocula. Samples were irradiated with aBL or washed for three consecutive days after which they were quantified. Colony-forming unit (CFU) counts were compared with a control group (bacterial inocula without treatment). After 1 day, aBL administered as a single 6 h dose or two 1 h doses spaced 6 h apart both reduced the CFU count by 1.63 log10 ± 0.02 CFU. Over 3 days of treatment, a positive aBL trend was observed with a maximum reduction of ~2.7 log10 CFU following 6 h of treatment, indicating a relation between multiple days of irradiation and greater CFU reductions. aBL was more effective at reducing the biofilm burden at the skin-implant interface compared with the wash group, demonstrating the potential of aBL as a biofilm management option.