Antimicrobial Activity of Ultraviolet C Light as a Potential Novel Treatment for Moraxella bovis Infection-An In Vitro Study.

Objective: To investigate the antimicrobial effect of 275 nm wavelength ultraviolet C (UV-C) light on M. bovis using an affordable, broadly available modified handheld device and to determine if photoreactivation plays a role in bacterial resistance to UV-C.

Methods: UV-C therapy (UVCT) was evaluated in vitro using triplicates of 3 M. bovis isolates from clinical cases. The UVCT was performed at a distance of 10, 15, and 20 mm with 1 or 2 doses (4 h apart) for 5, 15, or 30 s (s); the photoreactivation plates were exposed to 12 h of light at different times (T): T₀, T₄, T₆, and T₁₂ after the treatment.

Results: In vitro results showed all plates treated with UVCT had a 100% bactericidal effect for all the isolates with a single dose of 15 s at a 10 mm distance. At 15 and 20 mm of distance, 2 doses, 4 h apart, were needed for the same effect, or a single dose of 30 s, which had an 88.8% bactericidal effect. No bacterial regrowth was noticed macroscopically after exposure of the treated plates to artificial light at any time point.

Conclusions: The therapeutic potential for killing M. bovis was confirmed in vitro for all tested isolates using a single exposure of 15 s. UVCT can reduce the need for antibiotics, thereby shortening withdrawal periods for animal-derived food products, having a major impact on the cattle industry. Photoreactivation might not play a role in bacterial resistance to UV-C. While safety studies are underway, clinical trials are warranted.