Inhibitory Effect of Chitosan and Its Derivative on Enterococcus faecalis

Objectives: Enterococcus faecalis (E. faecalis) is commonly isolated from obturated root canals and saliva of endodontic patients. E. faecalis is responsible for persistent apical periodontitis. This study was aimed to explore the effects of chitosan and its derivative on Enterococcus faecalis and its biofilm.

Methods: E. faecalis ATCC 29212 and E. faecalis strains from an infected root canal and saliva were used in this study. Minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of chitosan (CS) and quaternary chitosan (HTCC) on E. faecalis were detected, respectively. Biofilms of the three E. faecalis strains were cultured on the dentin tablets (5mm x 5mm x 1mm) for 3 weeks, and then were subjected to CS and HTCC treatments, respectively. E. faecalis biofilms treated by CS and HTCC with MBC were observed via confocal laser microscopy after 24 h, 48 h and 72 h, respectively. The cytotoxicities of CS and HTCC in pre-osteoblastic MC3T3-E1 cells were detected using CCK-8 kit after 24 h, 48 h and 72 h, respectively.

Results: The MIC of CS and HTCC were 0.19mg/ml and 0.038mg/ml, respectively. The MBC of CS and HTCC were 0.38mg/ml and 0.075mg/ml, respectively. Compared with the negative control (saline), both CS and HTCC damaged the biofilm structure. There was no significant difference in the proportion of residual viable bacteria among CS and HTCC treatments and the positive control (2% sodium hypochlorite) (P>0.05). CS and HTCC could not inhibit the cell viability of MC3T3-E1 cells (P>0.05). The biocompatibility of CS and HTCC was markedly better than the positive control (2% sodium hypochlorite).

Conclusions: CS and HTCC have great potential to be applied in root canal disinfection.