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Antimicrobial Agents and Chemotherapy, July 2008, p. 2626-2631, Vol. 52, No. 7
0066-4804/08/$08.00+0     doi:10.1128/AAC.01666-07
Copyright © 2008, American Society for Microbiology. All Rights Reserved.

Genetic and Physiological Effects of Noncoherent Visible Light Combined with Hydrogen Peroxide on Streptococcus mutans in Biofilm {triangledown}

Doron Steinberg,1* Daniel Moreinos,1,2 John Featherstone,3 Moshe Shemesh,1 and Osnat Feuerstein2

Institute of Dental Sciences, Faculty of Dental Medicine, Hebrew University—Hadassah, Jerusalem, Israel,1 Department of Prosthodontics, Faculty of Dental Medicine, Hebrew University—Hadassah, Jerusalem, Israel,2 School of Dentistry, University of California San Francisco, San Francisco, California3

Received 25 December 2007/ Returned for modification 4 February 2008/ Accepted 25 February 2008

Oral biofilms are associated with the most common infections of the oral cavity. Bacteria embedded in the biofilms are less sensitive to antibacterial agents than planktonic bacteria are. Recently, an antibacterial synergic effect of noncoherent blue light and hydrogen peroxide (H2O2) on planktonic Streptococcus mutans was demonstrated. In this study, we tested the effect of a combination of light and H2O2 on the vitality and gene expression of S. mutans embedded in biofilm. Biofilms of S. mutans were exposed to visible light (wavelengths, 400 to 500 nm) for 30 or 60 s (equivalent to 34 or 68 J/cm2) in the presence of 3 to 300 mM H2O2. The antibacterial effect was assessed by microbial counts of each treated sample compared with that of the control. The effect of light combined with H2O2 on the different layers of the biofilm was evaluated by confocal laser scanning microscopy. Gene expression was determined by real-time reverse transcription-PCR. Our results show that noncoherent light, in combination with H2O2, has a synergistic antibacterial effect through all of the layers of the biofilm. Furthermore, this treatment was more effective against bacteria in biofilm than against planktonic bacteria. The combined light and H2O2 treatment up-regulated the expression of several genes such as gtfB, brp, smu630, and comDE but did not affect relA and ftf. The ability of noncoherent visible light in combination with H2O2 to affect bacteria in deep layers of the biofilm suggests that this treatment may be applied in biofilm-related diseases as a minimally invasive antibacterial procedure.

* Corresponding author. Mailing address: Institute of Dental Sciences, Faculty of Dental Medicine, Hebrew University—Hadassah, P.O. Box 12272, Jerusalem 91120, Israel. Phone: 972-2-6757633. Fax: 972-2-6758561. E-mail: dorons{at}cc.huji.ac.il

{triangledown} Published ahead of print on 3 March 2008.

Antimicrobial Agents and Chemotherapy, July 2008, p. 2626-2631, Vol. 52, No. 7
0066-4804/08/$08.00+0     doi:10.1128/AAC.01666-07
Copyright © 2008, American Society for Microbiology. All Rights Reserved.





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