Photodynamic bactericidal effect against Enterococcus faecalis by erythrosine concentration and LED irradiation times / 대한구강보건학회지

ABSTRACT

OBJECTIVES: The purpose of this study was to provide photodynamic bactericidal effect against Enterococcus faecalis by erythrosine concentrations and LED irradiation times. METHODS: Erythrosine was used as a photosensitizer and green LED (3 Watt, 520-530 nm) was used as light source. E. faecalis ATCC 1943 and E. faecalis ATCC 29212 were used in this study. Approximately 10(5) CFU of bacteria were added in wells of a 96-well microtitration plate. For examining the effects of concentrations of erythrosine, 0, 0.625, 1.25, 2.5, 5, and 10 microM of erythrosine were added in wells containing bacteria. The irradiation time with LED was 30 sec. In another set of experiment, the effect of irradiation time for killing of bacteria was investigated by increasing irradiation time from 0 to 30 s with 10 microM of erythrosine final concentration. After irradiation, each sample was serially diluted with PBS and 50 microl of diluents was spread on duplicate blood agar plates. The plates were incubated for 72 h at 37degrees C under aerobic conditions and the number of CFU was determined. The experiments were repeated four times. The results were analyzed using one-way ANOVA, and Tukey's multiple comparison at a significance level of 0.05. RESULTS: When the erythrosine concentrations were more than 2.5 microM, E. faecalis ATCC 29212 was significantly decreased (P<0.05). The more erythrosine concentrations increased, the more E. faecalis ATCC 1943 decreased statistically significantly (P<0.05). In another set of experiment, when LED irradiation time was more than 20 s, E. faecalis ATCC 1943 decreased significantly (P<0.05), and if the irradiation times was more than 5 s, E. faecalis ATCC 29212 decreased significantly (P<0.05). CONCLUSIONS: PDT using erythrosine and green LED was found to be an effective method in killing E. faecalis.