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Bacteria preferentially grow as colonies surrounded by a complex matrix, together called a biofilm. Biofilms are highly resistant to antibiotics and the immune system, making them difficult to treat at best, and nearly impossible to eradicate at worst. This presentation will describe a method which combines low energy, non-focused ultrasound with blue/violet light. Staphylococcus epidermidis, S. aureus, E. coli, and P. acnes biofilms were grown on hanging inserts (i.e. transwells) at 37°C for up to 72 hours before exposure. Following exposure to simultaneous ultrasound (at less than 100mW/cm2) and light energy (405nm), bacteria killing was quantified by serial dilution and plating on media agar. Killing was dose dependent with exposure time, and could be optimized with tuning of either the light or ultrasound energy. There was >1 log10 reduction after 5 min and >3 log10 reduction after 30 min treatment (p<0.05). Importantly, the two energies had to be delivered coincidentally for optimal effect. These initial results validated the basic mechanism: low intensity ultrasound “activates” the bacteria within the biofilm such that they become susceptible to the antimicrobial effects of blue light. A clinical system was then developed, safety tested, and submitted for IRB approval. Several clinical trials have been conducted which demonstrated not only a significant (~90%) reduction in facial P. acnes bacteria, but also a significant improvement in the appearance of acne vulgaris in test subjects. Bacteria reduction was dose dependent and statistically significant, and was not influenced by subject skin type. No adverse events were recorded.
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