Antibacterial property of chitosan against E. faecalis standard strain and clinical isolates.

To investigate applications of chitosan as antibacterial agent for endodontic treatments, we tested its activity against Enterococcus faecalis standard strain (ATCC29212) and clinical isolates. We determined the minimum bactericidal concentration (MBC) of 6 types of chitosan against ATCC29212; the most effective types were selected for further tests. Four clinical isolates were cultured from endodontically treated-teeth and identified by biochemical assays and polymerase chain reactions. Bacterial cultures were exposed to 1,700 and 2,100 kDa chitosan at MBC for 1, 3, 5, 10, and 60 min in time-kill assays and plated on brain-heart-infusion (BHI) agar for colony counts. Both types of chitosan showed significantly lower numbers of remaining bacteria (log colony forming units per millimeter, logCFUs/mL) than negative controls (0.1% acetic acid and BHI) at 10 min, and completely eliminated the bacteria at 60 min for all strains. Thus, chitosan could be developed as alternative biocompatible antimicrobial irrigant/medication for endodontic treatments.