Effects of extracellular polysaccharide and extracellular DNA on Enterococcus faecalis biofilm formation in human root cannal

Abstract

Objective To investigate the effects of extracellular polysaccharide and extracellular DNA on adhesion and biofilm formation of Enterococcus faecalis in ground sections of human dentin.Methods Ground sections of dentin were prepared and allocated to three groups: Dextranase group, DNaseI group and normal control group. Biofilm samples of Enterococcusfaecalis on dentin were obtained by culture in vitro. Colony-forming units (CFU) counts, confocal laser scanning microscope (CLSM) and COMSTAT software were used to measure the effect of extracellular polysaccharide on the bacterial adherence to dentin and the three dimensional structure of biofilm. Results Given a certain age of biofilm, less bacterial adherence of Enterococcus faecalis to dentin was found in both Dextranase and DNaseI group than that in normal control group (P＜0.05). The 1-h bacterial adherence in these two groups was 15.61% and 18.39% less, respectively, as compared with the normal control group. CLSM showed that treatment with Dextranase or DNaseI may affected dentin biofilm formation: loosened biofilm structure and reduction in biomass, bottom coverage and mean thickness (P＜0.0167). Notably, the biomass in Dextranase and DNaseI group decreased significantly from ( 3.95 ± 0.09 ) μm3/μm2 to (0.36 ± 0.08 ) μm3/μm2 and ( 1.05 ± 0.06 ) μm3/μm2, respectively.DNaseI but not Dextranase was shown to degrade the mature biofilms on dentin. Conclusion Extracellular polysaccharide and extracellular DNA may be important components of Enterococcus faecalis bioflim structure, which contribute significantly to initial bacterial adhesion and three dimensional biofilm structure. Key words: Enterococcus faecalis; Biofilm; Extracellular matrix; Dentin; Dextranase