RÉSUMÉ
OBJECTIVES: In the present study, the effectiveness of Photodynamic Antimicrobial Chemotherapy (PACT) was evaluated on planktonic cells and biofilms of five Enterococcus faecalis clinical isolates. METHODS: Planktonic cells and biofilms of E. faecalis E2, E3, ER3/2s, OS16 and AA-OR34 were grown in SDMY medium plus 0.4% glucose. Approximately 5.0×10(7)CFU planktonic cells and 24h biofilms were subjected to PACT using the combination of Light Emitting Diodes (LEDs, Biotable(®)) and Photogem(®). The metabolic activity of bacterial cells was evaluated by a resazurin assay. Biomass values of the biofilms were determined by a crystal violet assay. RESULTS: Compared to the water-treated control group, gradual increases of light energy led to greater reduction of metabolic activity of planktonic cells and biofilms of E. faecalis when the combination of LEDs and Photogem(®) was applied. Photogem(®) alone significantly reduced the metabolic activity of planktonic cells, whereas LEDs or Photogem(®) alone did not result in biofilm viability changes. PACT yielded similar antimicrobial outcomes on planktonic cells of all tested E. faecalis strains, whereas biofilms of E. faecalis E3, ER3/2s and OS16 were more resistant to PACT than biofilms of E. faecalis E2 and AA-OR34. CONCLUSIONS: The efficacy of PACT on E. faecalis biofilms was strain dependent. PACT demonstrated its potential as an adjuvant antimicrobial treatment by killing of E. faecalis planktonic and biofilm cells.