Investigating microbial mitigation for surgical incision sites using UV-C

Authors:
Benjamin Robertson, Christopher Jones, David Brenner, Deborah Mosca, Eric Prast, Ernest Blatchley III, Karl Linden, Katja Auer, Nancy Havill, Richard Rasansky

Body of Abstract:
Background
Surgical site infections (SSIs) are a serious complication following surgery, requiring additional antibiotics, prolonged hospitalizations, or hospital readmission. The emergence of multidrug-resistant pathogens has diminished the effectiveness of traditional antimicrobials thus requiring a new approach to prevention and treatment. We are developing an innovative device (xIP) that uses UV-C to inactivate pathogens in surgical incision sites, mitigating the risk of developing an SSI.
Irradiation in the UV-C range (200-280 nm) is well known to inactivate pathogens by damaging DNA and RNA. Despite its known effectiveness in surface and aerosol pathogen inactivation, there is a limited body of work for the application of UV-C on surgical sites.

Methods

To assess disinfection in the UV-C range we explored three sources. A Krypton-Chloride Excimer (KrCl*) lamp ( peak = 222 nm), a pulsed Xenon (PX) emitter (broad spectrum), and a UVC LED ( peak = 282 nm). Inactivation of Escherichia coli (E. coli, ATCC 29425) and methicillin-resistant Staphylococcus aureus (MRSA, USA300) was determined by in vitro exposure to UV-C at doses of 0 (control), 2, 5, 10, 15, and 20mJ/cm2.

Microbial suspensions of log-phase cultures were pelletized and resuspended in phosphate buffered saline three times. The adjusted suspension concentration of ~109 CFU/mL was then diluted to 107 CFU/mL. After UV exposure, suspensions were plated on an agar substrate using a grid-based method. After incubating for 48 hours at 37°C, remaining viability was determined.

Results

For all emitters, we observed a 4.5-5+ log reduction in MRSA and 4-5+ log reduction in E. coli at the highest UV dose (20mJ/cm2). PX and KrCl* emitters both showed peak inactivation of 5+ in both test microorganisms, while LED showed 4 and 4.5 log reduction in E. coli and MRSA, respectively. PX demonstrated the highest inactivation efficiency (log-reduction per unit dose), followed by KrCl* and LED.

Conclusions

In-vitro data suggest that surgical sites could be effectively treated in less than a minute with a small hand-held device and less than 10 seconds with a larger device. Inactivation of MRSA using a superficial wound model in hairless SHKI1-elite mice (Charles River strain code 477) is in progress.

In-silico modelling using optical raytracing is in progress to understand the impact of wound and skin micro-environment on the performance of the device. These data will help inform ex-vivo testing using porcine or surrogate human skin (EpiDerm FT) models to evaluate the performance of our device in different wound types such as incisions, abrasions, and punctures as well as the impact of fluids such as saline and blood.

Development of the xIP device is underway in collaboration with healthcare professionals to produce a product that is effective, fits into current practice, and is broadly automated. Upon successful completion of a prototype device, clinical efficacy will be explored.