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Coincident Light/Ultrasound Therapy to Treat Bacterial Biofilms
Abstract   Open access

Coincident Light/Ultrasound Therapy to Treat Bacterial Biofilms

Mark Evan Schafer and Tessie McNeely
Ultrasound in medicine & biology, v 41(4 Supplement), pp S63v-S64
Apr 2015
DOI: https://doi.org/10.1016/j.ultrasmedbio.2014.12.272
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https://doi.org/10.1016/j.ultrasmedbio.2014.12.272View
Published, Version of Record (VoR)Maybe Open Access (Publisher Bronze),  Open

Abstract

Objectives : Bacteria preferentially grow as colonies surrounded by a complex matrix, together called a biofilm. According to the NIH over 80% of microbial infections in the human body consist of biofilms. We propose to treat bacterial biofilms by simultaneous exposure to low energy, non-focused ultrasound, combined with blue/violet light (i.e. CLENS™: Coincident Light Energy and Non-focused ultraSound). Low intensity ultrasound has previously been explored for anti-biofilm activity, however it has generally been applied in conjunction with an antibiotic. Similarly, blue/violet light has been explored as a bactericidal agent for planktonic bacteria. We hypothesize that the simultaneous application of blue/violet light with ultrasound synergizes the beneficial properties of each, and successfully provides a technologically new method to attack biofilms. Methods : prototype laboratory device was built to deliver simultaneous ultrasound and light energy to bacterial biofilm grown in-vitro. Light emitting diodes (LEDs) were used to generate 30mW/cm2; and a coincident ultrasound source created a pressure field at less than 100mW/cm2. Staphylococcus epidermidis, S. aureus, and P. acnes were grown on hanging inserts (i.e. transwells) at 37°C for up to 72 hours before exposure. After CLENS exposure, the inserts were rinsed with PBS and stained using either 0.1% Crystal Violet, which stains the bacteria and biofilm matrix, or with BacLight (Molecular Probes), which is a live/dead stain observable under a fluorescent microscope. Results : A 20 minute treatment showed significant cell death, specifically in regions where the ultrasound and light energies overlapped. Large clusters of biofilm/bacteria were significantly reduced and in some cases completely eliminated. A 60 minute treatment caused the biofilm to completely release from the PET membrane. Conclusions : These initial results validate that the basic CLENS mechanism is effective on relevant biofilm-producing bacteria: low intensity ultrasound “activates” the bacteria within the biofilm such that they become susceptible to the antimicrobial effects of blue light.

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