Evaluation of Low-Dose Ultraviolet Light C for Reduction of Select ESKAPE Pathogens in a Canine Skin and Muscle Model

This study aimed at comparing the ability of low-dose UVC, 0.05% chlorhexidine, and combined UVC with 0.05% chlorhexidine to reduce colony-forming units (CFUs) on select ESKAPE pathogens (Staphylococcus aureus, Klebsiella pneumoniae, and Enterococcus faecium) in a canine skin and muscle model.

Surgical site infections (SSIs) result in increased morbidity and cost. UVC damages DNA, rendering bacteria nonviable and does not discriminate between drug-sensitive and multi-drug-resistant organisms.

Specimens were inoculated with one of three pathogens. Samples were treated with a 254 nm UVC mercury lamp or a 270 nm UVC LED light at 0.015, 0.03, or 0.04 J/cm(2) doses; 0.05% and 2% chlorhexidine were used as positive controls. To evaluate synergism, 0.05% chlorhexidine was used with 0.015 J/cm(2) of UVC. CFUs were counted and compared against the negative control.

There were no significant differences in CFU counts between samples of the same tissue type treated with different light sources of the same UVC dose. UVC significantly decreased CFUs when compared against all negative controls in both skin and muscle. There was no consistently superior bactericidal UVC dose identified for individual bacteria or for tissue type. The bactericidal activity of UVC at 0.015 J/cm(2) versus 0.05% chlorhexidine was not different in muscle for any bacteria. The bactericidal activity of UVC at 0.015 J/cm(2) was superior to 0.05% chlorhexidine in skin for S. aureus and K. pneumonia, but not E. faecium. Combination of UVC and 0.05% chlorhexidine showed synergy against E. faecium when evaluated on skin.

Low-dose UVC shows promise as a rapid, effective, and synergistic means of reducing bacterial burdens, which may decrease the incidence of SSIs. It should be further evaluated for use when 2% chlorhexidine would be contraindicated or impractical, such as open wounds or surgical sites.