the effect of antimicrobial photodynamic therapy with radachlorin® on staphylococcus aureus and escherichia coli: an in vitro study

introduction: the a im of this study is the evaluation of the effect of antimicrobial photodynamic therapy with radachlorin on staphylococcus aureus and escherichia coli. new windows are open in the antimicrobial field so-call photodynamic therapy that incorporates a nonpoisonous photosensitizer (ps) with innocuous special wavelength photons to excite the ps. methods: two strains of bacteria used in this study were methicillin resistant staphylococcus aureus (atcc 33591; ptcc 1764) and escherichia coli (atcc 25922; ptcc1399). concentrations of 0.2 ml of radachlorin® were applied on 0.2 ml of bacterial suspensions and placed in a 48-well microtiter plate. the following groups were used: (i) l− ps− (no laser, no photosensitizer), (ii) l−ps+ (treated only with ps), (iii) l+ ps− (treated only with laser) and (iv) l+ ps+ (treated with laser and ps: photodynamic therapy group). aliquots of bacterial suspensions were sensitized with radachlorin® for 15 minutes in the dark at room temperature and then bacterial suspensions in group iii and iv were irradiated with 210 mw (power density) and 12 j/cm2 (energy density) on continuous mode. results: this study showed that photodynamic therapy reduces 0.14 log 10 in e.coli (group iv) and there were significant differences for group iv (p<0.01). photodynamic therapy in s.aureus showed 6.28 log 10 colony count reduction (group iv) and there were highly significant differences in photodynamic therapy group (p<0.0001). conclusion: radachlorin® have bactericidal effect on s.aureus (6.28 log 10) and bacteriostatic effect on e.coli (0.14 log 10).