A laboratory investigation of photo-activated disinfection (PAD) to enterococcus faecalis

Abstract

OBJECTIVE: The aims of this study were to investigate the effect of Photo-Activatied Disinfection (PAD) on Enterococcus faecalis in a laboratory model to find the relationship between the irradiation energy and bacterial kill. Methods: The experiments were carried out in small glass tubes containing a measured volume of Enterococcus faecalis with high concentration and photosensitizer (tolonium chloride with low concentration). The suspension of Enterococcus faecalis was exposed to a 635-nm diode laser light, and the range of energy doses (J) was from 0.5J to 4.5J produced by varying power (mW) and time (T). The treatment were evaluated for bactericidal effect by calculating colony forming units (CFU) from every irradiated and control specimen and comparing the number of viable bacteria remaining. RESULTS: Analysis of linear regression and Student's T test were performed (level of significance set at p≤0.05). The number of Enterococcus faecalis was significantly reduced when energy dose reached 0.5J. Energy doses of 4.5J produced 100% kills to 1E+14 cfu/ml Enterococcus faecalis. Conclusion: It is concluded that PAD was shown to have a high bactericidal effect to killed up to 1E+14 cfu/ml Enterococcus faecalis with using irradiated low concentration tolonium chloride and this effect was related to the energy delivered by the diode laser light.