The effects of violet and blue light irradiation on ESKAPE pathogens and human cells in presence of cell culture media

Richard Bauer,Richard Bauer,Martin Hessling,Katharina Hoenes,Tobias Meurle,Barbara Spellerberg,Barbara Spellerberg

doi:10.1038/s41598-021-04202-x

Abstract

Bacteria belonging to the group of ESKAPE pathogens are responsible for the majority of nosocomial infections. Due to the increase of antibiotic resistance, alternative treatment strategies are of high clinical relevance. In this context visible light as disinfection technique represents an interesting option as microbial pathogens can be inactivated without adjuvants. However cytotoxic effects of visible light on host cells have also been reported. We compared the cytotoxicity of violet and blue light irradiation on monocytic THP-1 and alveolar epithelium A549 cells with the inactivation effect on ESKAPE pathogens. THP-1 cells displayed a higher susceptibility to irradiation than A549 cells with first cytotoxic effects occurring at 300 J cm−2 (405 nm) and 400 J cm−2 (450 nm) in comparison to 300 J cm−2 and 1000 J cm−2, respectively. We could define conditions in which a significant reduction of colony forming units for all ESKAPE pathogens, except Enterococcus faecium, was achieved at 405 nm while avoiding cytotoxicity. Irradiation at 450 nm demonstrated a more variable effect which was species and medium dependent. In summary a significant reduction of viable bacteria could be achieved at subtoxic irradiation doses, supporting a potential use of visible light as an antimicrobial agent in clinical settings.

Highlights

Bacteria belonging to the group of ESKAPE pathogens are responsible for the majority of nosocomial infections
Both studies showed the presence of a therapeutic window for light application as the keratinocytes survived the irradiation with a dose of 109.9 J cm−2 and 170 J cm−2, whereas P. aeruginosa and S. aureus cell densities were reduced by several log levels[18,19]
Cells incubated in the dark served as negative control and resulted in around 10% dead cells after 22 h incubation for THP-1 and less than 5% for A549 cells (Fig. S1)

Summary

Introduction

Bacteria belonging to the group of ESKAPE pathogens are responsible for the majority of nosocomial infections. Due to the increase of antibiotic resistance, alternative treatment strategies are of high clinical relevance In this context visible light as disinfection technique represents an interesting option as microbial pathogens can be inactivated without adjuvants. We compared the cytotoxicity of violet and blue light irradiation on monocytic THP-1 and alveolar epithelium A549 cells with the inactivation effect on ESKAPE pathogens. Microbial inactivation through visible light is based on photo-excitation of intracellular photosensitizers These molecules absorb photons of a certain wavelength which induces an oxygen dependent photo-excitation reaction within the bacterial cell[9]. Similar to the effect in bacterial cells, visible light irradiation can lead to the generation of ROS in human cells[29,30,31]. The cytotoxicity in human cells seems to be dose dependent[32,35] and light in the violet range induces higher toxicity than blue light[36]

Methods

Results

Conclusion