Optimization of the antimicrobial effect of blue light on methicillin-resistant Staphylococcus aureus (MRSA) in vitro

• Published in: Lasers in surgery and medicine 2015-03, Vol.47 (3), p.266-272
• Main Authors: Bumah, Violet V., Masson-Meyers, Daniela S., Cashin, Susan, Enwemeka, Chukuka S.
• Format: Article
• Language: English
• Subjects: antimicrobial blue light; bacteria suppression; Colony Count, Microbial; Light; methicillin-resistant Staphylococcus aureus; Methicillin-Resistant Staphylococcus aureus - radiation effects; phototherapy; Staphylococcus aureus
• ISSN: 0196-8092; 1096-9101
• DOI: 10.1002/lsm.22327

Background and Objective In previous studies, we showed that irradiation with 405 nm or 470 nm light suppresses up to 92% methicillin‐resistant Staphylococcus aureus (MRSA) growth in vitro and that the remaining bacteria re‐colonize. In this study, the aim was to develop a protocol that yields 100% MRSA growth suppression. Materials and Methods We cultured 3 × 106 and 5 × 106 CFU/ml USA300 strain of MRSA and then irradiated each plate with varying fluences of 1–60 J/cm2 of 405 nm or 470 nm light, either once or twice at 6 hours intervals. Next, we plated 7 × 106 CFU/ml and irradiated it with 45, 50, 55, or 60 J/cm2 fluence, once, twice, or thrice at the same 6 hours intervals. In a third experiment, the same culture density was irradiated with 0, 165, 180, 220, or 240 J/cm2, either once, twice, or thrice. Results Irradiation with either wavelength significantly reduced the bacterial colonies regardless of bacterial density (P