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Research Article | 27 Jul 2025

Selective bactericidal efficacy of 465-nm blue light phototherapy against standard and canine wound pathogens: An in vitro evaluation

Pimsiri Ngowwatana1 ORCID , Naruepon Kampa1 ORCID , Somphong Hoisang1 ORCID , Suvaluk Seesupa1 ORCID , Duangdaow Khunbutsri2 ORCID , Saikam Chaimongkol3 ORCID , Preenun Jitasombuti1 ORCID , Supranee Jitpean1 ORCID , Thanikul Srithunyarat1 ORCID , Chalermkwan Nonthakotr3 ORCID , Nitaya Boonbal3 ORCID , Piyasak Wipoosak3 ORCID , and Duangdaun Kaenkangploo1 ORCID Show more
VETERINARY WORLD | Article No. 26 | pg no. 2064-2071 | Vol. 18, Issue 7 | DOI: 10.14202/vetworld.2025.2064-2071
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ABSTRACT

                      
Background and Aim: Antibiotic resistance poses a growing threat to wound management in veterinary medicine. Blue light phototherapy has emerged as a non-antibiotic bactericidal alternative with additional benefits for wound healing. However, its effectiveness in clinical veterinary contexts remains inadequately explored. This study evaluated the bactericidal efficacy of 465-nm blue light against standard pathogens and bacteria isolated from infected canine wounds, aiming to determine optimal energy doses for clinical use.
Materials and Methods: Three standard bacterial strains – Staphylococcus aureus (American Type Culture Collection [ATCC] 25923), Pseudomonas aeruginosa (ATCC 27853), and Escherichia coli (ATCC 25922) – along with five clinical isolates from canine wounds, were exposed to 465-nm blue light at energy doses of 28, 56, and 112 J/cm2 (15, 30, and 60 min, respectively). Colony-forming units (CFUs) were quantified post-irradiation and compared to non-irradiated controls. Statistical significance was assessed using appropriate parametric and non-parametric tests.
Results: P. aeruginosa (ATCC 27853) exhibited significant, dose-dependent inhibition at all energy doses, resulting in reductions of 36.3%, 60.5%, and 82.8%. Clinical P. aeruginosa isolates demonstrated 21.1% and 78.8% inhibition at 56 and 112 J/cm2, respectively (p < 0.05). E. coli (ATCC 25922) was significantly inhibited only at 112 J/cm2 (46.4% reduction, p = 0.045). No significant reductions were observed for S. aureus, Acinetobacter baumannii, Staphylococcus haemolyticus, clinical E. coli, or Enterococcus faecalis at any dose.
Conclusion: Blue light at 465-nm exhibits selective bactericidal activity, effectively inhibiting P. aeruginosa and E. coli (ATCC), with efficacy dependent on bacterial species and applied energy dose. Its limited effect on other pathogens underscores the importance of species-specific treatment planning. Higher energy doses (112 J/cm2) may be required in unknown or mixed infections. Further investigation is recommended to refine device specifications and assess clinical utility in veterinary settings.
                      
Keywords: antimicrobial resistance, blue light therapy, Escherichia coli, photoinactivation, Pseudomonas aeruginosa, veterinary phototherapy.