Streptococcus mutans, Aggregatibacter actinomycetemcomitans, and DPB were cultured in brain-heart infusion (BHI) broth (Becton, Dickinson and Company, Baltimore, MD) at 37 °C with shaking at 200 rpm. Dental plaques were obtained through regular scaling from a participant without any oral mucosal disease and all procedures were performed by dental hygienist. Informed consent was given by the participant. Cells were harvested and PBS-washed three times by centrifugation at 3,000 rpm for 5 min. The washed cells were suspended in PBS and absorbance was measured at 600 nm using a DU 800 spectrophotometer (Beckman Coulter, Palo Alto, CA). A standard curves was generated for each bacterial sample and colony forming units (CFU)/ml was determined. For experiments requiring plate cultures, a bacterial suspension was subcultured onto the surface of BHI agar and bacterial growth was assessed. To stimulate the cultured cells, a multiplicity of infection (MOI) of 200 bacteria was applied for 24 h at 37 °C and 5% CO2.