UV light assisted antibiotics for eradication of in vitro biofilms

Aikaterini Argyraki,Paul Michael Petersen,Lars Bjørndal,Thomas Bjarnsholt,Merete Markvart,Kasper Nørskov Kragh,Yiyu Ou,Camilla Stavnsbjerg

doi:10.1038/s41598-018-34340-8

Aikaterini Argyraki, Paul Michael Petersen + Show 6 more

Open Access

https://doi.org/10.1038/s41598-018-34340-8

Copy DOI

Abstract

The overuse of antibiotics is accelerating the bacterial resistance, and therefore there is a need to reduce the amount of antibiotics used for treatment. Here, we demonstrate in vitro that specific wavelengths in a narrow range around 296 nm are able to eradicate bacteria in the biofilm state (grown for 24 hours) more effectively, than antibiotics and the combination of irradiation and antibiotics is even better, introducing a novel concept light assisted antibiotics. The investigated wavelength range was 249 nm to 338 nm with an approximate step of 5 nm. The novel concept that consists of a UV irradiation treatment followed by a tobramycin treatment can significantly reduce the amount of antibiotics needed for eradicating mature bacterial biofilms. The efficiency of the proposed light assisted antibiotics method was compared to combinatory antibiotic treatment and highly concentrated antibiotic monotherapy. The eradication efficacies, on mature biofilms, achieved by light assisted antibiotic and by the antibiotic monotherapy at approximately 10-fold higher concentration, were equivalent. The present achievement could motivate the development of light assisted antibiotic treatments for treating infections.

Highlights

There is a worldwide increasing awareness and concern about the antibiotic resistance, which in the future could prevent effective treatment of a large number of infectious diseases[1]
Where Ntreated is the number of colony forming units (CFUs) per micropore filter after a treatment is applied to the biofilm, and N control is the number of CFUs per micropore filter of non-treated samples
We have tested the efficiency of UV irradiation treatments to eradicate P. aeruginosa biofilms grown for 24 h in the wavelength range 249 nm to 338 nm with an approximate step of 5 nm

Summary

Introduction

There is a worldwide increasing awareness and concern about the antibiotic resistance, which in the future could prevent effective treatment of a large number of infectious diseases[1]. Biofilm infections are highly persistent to the immune response and known for their tolerance to antibiotic treatments[3]. Alternative approaches, different than conventional antibiotic treatments, are gaining increasing interest and light based treatments[4] are unconventional strategies for biofilm eradication. The ultraviolet (UV) wavelength dependent eradication efficiency for Pseudomonas aeruginosa biofilms has not been reported. External quantum efficiency (EQE) of UV LEDs is continuously improving as both internal quantum efficiency (IQE) and light extraction efficiency (LEE) are boosted by various techniques like: migration-enhanced metalorganic chemical vapor deposition[9,10], ammonia pulsed-flow method[11,12] and nanowires[13], or surface plasmons[14] and aluminum reflective electrodes[15], respectively. Combinatory therapies seem to be the solution for combating tolerant biofilms present in chronic infections[17,18]. The physical barrier of the biofilm matrix, limits the diffusion of molecules[25] into the biofilm, and reduces antimicrobial penetration

Objectives

Methods

Results

Discussion

Conclusion