Dynamics of anti-M antibody response in a mouse model following intranasal infection with group A Streptococcus M-18

Light activated antimicrobial agents can inactivate oral malodour causing bacteria

Oral malodour is a common condition which affects a large proportion of the population, resulting in social, emotional and psychological stress. Certain oral bacteria form a coating called a biofilm on the tongue dorsum and degrade organic compounds releasing volatile sulfur compounds that are malodourous. Current chemical treatments for oral malodour such as mouthwashes containing chlorhexidine or essential oils, are not sufficiently effective at reducing the bacterial load on the tongue. One potential alternative to current chemical treatments for oral malodour is the use of light activated antimicrobial agents (LAAAs), which display no toxicity or antimicrobial activity in the dark, but when exposed to light of a specific wavelength produce reactive oxygen species which induce damage to target cells in a process known as photodynamic inactivation. This study aimed to determine whether oral malodour causing bacteria were susceptible to lethal photosensitization. Five bacterial species that are causative agents of oral malodour were highly sensitive to lethal photosensitization and were efficiently killed by methylene blue in conjunction with 665 nm laser light. Between 4.5-5 log₁₀ reductions in the number of viable bacteria were achieved with 20 µM methylene blue and 14.53 J cm^-2 laser light for Porphyromonas gingivalis, Prevotella intermedia, Peptostreptococcus anaerobius and Solobacterium moorei. The number of viable cells fell below the limit of detection in the case of Fusobacterium nucleatum. These findings demonstrate that methylene blue in combination with 665 nm laser light is effective at killing bacteria associated with oral malodour, suggesting photodynamic therapy could be a viable treatment option for oral malodour.

Effect of hydrosoluble chlorine-mediated antimicrobial photodynamic therapy on clinical parameters and cytokine profile in ligature-induced periodontitis in dogs

BACKGROUND

Recently, a hydrosoluble chlorine composed of sodium salts chlorine e6, chlorine p6, and purpurine-5 has been shown to be a promising photosensitizer in antimicrobial photodynamic therapy (aPDT). The aim of this study is to evaluate the effects of adjunctive application of hydrosoluble chlorine-mediated aPDT compared with scaling and root planing (SRP) alone on clinical parameters and cytokine levels in gingival crevicular fluid of dogs with experimental periodontitis.

METHODS

Periodontal disease was induced by placing silk ligatures around both maxillary and mandibular teeth. After establishment of attachment loss, full-mouth SRP was performed in all dogs. One day after SRP, each quadrant randomly received one of the following treatment modalities: hydrosoluble chlorine plus diode laser (wavelength 662 nm, power 100 mW, continuous mode, time of irradiation 20 seconds), hydrosoluble chlorine alone, laser alone, or no adjunctive treatment. The same adjunctive procedure was repeated 1 week later. Clinical parameters including periodontal probing depth, clinical attachment level, and bleeding on probing, as well as crevicular levels of interleukin-1β and tumor necrosis factor-α, were evaluated at baseline, at 3 weeks, and at 3 months after treatment.

RESULTS

After both 3 weeks and 3 months, all treatment groups showed significant improvement in all clinical and immunologic parameters (P <0.001). No significant differences were found between the four groups with regard to the measured parameters (P >0.05).

CONCLUSION

Based on the results of this study, adjunctive use of hydrosoluble chlorine-mediated aPDT with the current setting has no additional effect on the clinical parameters or proinflammatory cytokine levels in ligature-induced periodontitis.