Effects of sub-lethal dose of antimicrobial photodynamic therapy on major virulence traits of Streptococcus mutans.

BACKGROUND Antimicrobial photodynamic therapy (aPDT) as a complementary step of selective removal of dental caries appears as an ideal choice to help manage caries with minimal interventions. Sub-lethal dose of aPDT (sPDT) impressively affects microbial virulence, although it does not kill microorganisms. Therefore, the present study aimed to investigate the influence of sPDT using diode laser plus chlorophyllin-phycocyanin mixture (PhotoActive+) on changes in gtfB gene expression and the subsequent protein expression of GtfB. MATERIALS AND METHODS sPDT using PhotoActive+ and 635 ± 10 nm diode laser was used to examine the expression of gtfB mRNA and GtfB protein expression of Streptococcus mutans by quantitative Real time PCR (qRT-PCR) method and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), respectively. RESULTS In this study, sPDT using 2.4 × 10-3 mol/L PhotoActive+ with 3 min irradiation time of diode laser with energy density of 104 J/cm2, significantly reduced the gtfB gene expression with rates of 3.5-fold (P < 0.05). Also, PhotoActive+ mediated sPDT demonstrated a significant reduction in GtfB protein expression of S. mutans up to 54% (P < 0.05). CONCLUSIONS This study demonstrated the potential effect of PhotoActive+ mediated sPDT on one of the most important virulence factors of S. mutans.