Pulsed 450 nm blue light suppresses MRSA and Propionibacterium acnes in planktonic cultures and bacterial biofilms

Violet Vakunseh Bumah; Daniela Santos Masson-Meyers; Chukuka Samuel Enwemeka

doi:10.1016/j.jphotobiol.2019.111702

Pulsed 450 nm blue light suppresses MRSA and Propionibacterium acnes in planktonic cultures and bacterial biofilms

J Photochem Photobiol B. 2020 Jan:202:111702. doi: 10.1016/j.jphotobiol.2019.111702. Epub 2019 Nov 12.

Authors

Violet Vakunseh Bumah¹, Daniela Santos Masson-Meyers², Chukuka Samuel Enwemeka³

Affiliations

¹ Department of Chemistry and Biochemistry, College of Sciences, San Diego State University, 5500 Campanile Dr, San Diego, CA 92182, USA. Electronic address: vbumah@sdsu.edu.
² College of Health and Human Services, San Diego State University, 5500 Campanile Dr, San Diego, CA 92182, USA.
³ College of Health and Human Services, San Diego State University, 5500 Campanile Dr, San Diego, CA 92182, USA. Electronic address: enwemeka@sdsu.edu.

PMID: 31760372
DOI: 10.1016/j.jphotobiol.2019.111702

Abstract

In our recent study, we showed that pulsed blue light (PBL) suppresses the growth of Propionibacterium acnes more than continuous wave (CW) blue light in vitro, but it is not known that other bacteria, such as methicillin-resistant Staphylococcus aureus (MRSA), respond similarly to PBL. The high potency of PBL relative to CW blue light makes it a suitable antimicrobial for suppressing bacterial growth in biofilms as well. Therefore, we determined if MRSA-a deadly bacterium of global concern-is susceptible to 450 nm PBL irradiation in vitro, and ascertained whether the bactericidal effect of PBL on planktonic P. acnes culture can be replicated in biofilms of P. acnes and MRSA. In three series of experiments, we irradiated P. acnes and MRSA respectively, either in planktonic cultures, forming biofilms or formed biofilms. Compared to controls, the results showed 100% bacterial suppression in planktonic cultures of MRSA irradiated with 3 mW/cm² irradiance and 7.6 J/cm² radiant exposure three times at 30-minute intervals, and also in P. acnes cultures irradiated with 2 mW/cm² irradiance 5 J/cm² radiant exposure thrice daily during each of 3 days. Irradiation of biofilms with the same irradiances and radiant exposures that gave 100% bacterial suppression in planktonic cultures resulted in disruption and disassembly of the architecture of MRSA and P. acnes biofilms, more so in forming biofilms than formed biofilms. The antimicrobial effect on each bacterium was minimal in forming biofilms, and even less in formed biofilms. Increasing radiant exposure slightly from 7.6 J/cm² to 10.8 J/cm² without changing any other parameter, yielded more disruption of the biofilm and fewer live MRSA and P. acnes, suggesting that 100% bacterial suppression is possible with further refinement of the protocol. In both planktonic cultures and biofilms, PBL suppressed MRSA more than P. acnes.

Keywords: Antimicrobial therapy; Biofilm; Methicillin-resistant Staphylococcus aureus; PBM; Printed LEDs; Propionibacterium acnes.

MeSH terms

Biofilms / radiation effects*
Disk Diffusion Antimicrobial Tests
Light*
Methicillin-Resistant Staphylococcus aureus / physiology*
Methicillin-Resistant Staphylococcus aureus / radiation effects*
Microscopy, Fluorescence
Propionibacterium acnes / physiology
Propionibacterium acnes / radiation effects*
Thermodynamics