Antimicrobial activity of hydroxyl radicals generated by hydrogen peroxide photolysis against Streptococcus mutans biofilm

作者：Nakamura Keisuke; Shirato Midori; Kanno Taro; Ortengren Ulf; Lingstrom Peter; Niwano Yoshimi

来源：International Journal of Antimicrobial Agents, 2016, 48(4): 373-380.

DOI：10.1016/j.ijantimicag.2016.06.007

• Biofilm
• Confocal laser scanning microscopy
• Hydrogen peroxide
• Hydroxyl radical
• Photolysis
• Streptococcus mutans

Prevention of dental caries with maximum conservation of intact tooth substance remains a challenge in dentistry. The present study aimed to evaluate the antimicrobial effect of H2O2 photolysis on Streptococcus mutans biofilm, which may be a novel antimicrobial chemotherapy for treating caries. S. mutans biofilm was grown on disk-shaped hydroxyapatite specimens. After 1-24 h of incubation, growth was assessed by confocal laser scanning microscopy and viable bacterial counting. Resistance to antibiotics ( amoxicillin and erythromycin) was evaluated by comparing bactericidal effects on the biofilm with those on planktonic bacteria. To evaluate the effect of the antimicrobial technique, the biofilm was immersed in 3% H2O2 and was irradiated with an LED at 365 nm for 1 min. Viable bacterial counts in the biofilm were determined by colony counting. The thickness and surface coverage of S. mutans biofilm increased with time, whereas viable bacterial counts plateaued after 6 h. When 12- and 24-h-old biofilms were treated with the minimum concentration of antibiotics that killed viable planktonic bacteria with 3 log reduction, their viable counts were not significantly decreased, suggesting the biofilm acquired antibiotic resistance by increasing its thickness. By contrast, hydroxyl radicals generated by photolysis of 3% H2O2 effectively killed S. mutans in 24-h-old biofilm, with greater than 5 log reduction. The technique based on H2O2 photolysis is a potentially powerful adjunctive antimicrobial chemotherapy for caries treatment.

• 出版日期2016-10