The in vitro effect of antimicrobial photodynamic therapy with indocyanine green on Enterococcus faecalis: Influence of a washing vs non-washing procedure.

INTRODUCTION: The purpose of this study was to evaluate the in vitro effect of washing and non-washing of indocyanine green (ICG) as photosensitizer (PS) on bacterial count, biofilm formation, development and degradation of Enterococcus faecalis.

METHODS: The anti-bacterial, anti-biofilm formation, anti-biofilm development and biofilm degradation of anti-microbial photodynamic therapy (aPDT) against E. faecalis was determined at concentrations of 3 to 2000μg/mL of ICG, subject to 18J/cm(2) dose of diode laser (808nm) in washing and non-washing producers. Bacterial viability measurements and biofilm assays were evaluated by broth microdilution method and crystal violet assays, respectively.

RESULTS: ICG-mediated aPDT, using 25 to 2000μg/mL and 50 to 2000μg/mL showed significant reduction in E. faecalis growth when compared to the control in non-washing and washing producers, respectively (P<0.05). Also, ICG-mediated aPDT showed a significantly inhibitory effect on biofilm formation of E. faecalis in concentration of 6 to 2000μg/mL and 100 to 2000μg/mL in non-washing and washing groups (P<0.05). The biofilm development was inhibited by concentrations of 12 to 2000μg/mL and 100 to 2000μg/mL in non-washing and washing groups. The biofilm degradation increased from concentrations of 12 to 2000μg/mL and 250 to 2000μg/mL in non-washing and washing groups, respectively.

CONCLUSION: This study shows that the application of ICG should be accompanied by laser irradiation without being washed out to achieve better result for bacterial count reduction and anti-biofilm effects.