Comparative evaluation of disinfection mechanism of sodium hypochlorite, chlorine dioxide and electroactivated water on Enterococcus faecalis

Abstract

The aim of this study is to compare the efficiency of chlorine-based disinfectants, namely, sodium hypochlorite (NaOCl), chlorine dioxide (ClO2), and electroactivated water (EAW), and to investigate their inactivation mechanisms on a Gram positive, opportunistic pathogen Enterococcus faecalis. Cell viability, damages on membrane integrity and cellular components were examined to reveal underlying mechanisms of the disinfection process. Among three disinfectants, EAW was the most effective one to inactivate E. faecalis in less time with more damage. According to flow cytometry results, EAW destroyed 95.4% of bacteria within 1 min whereas NaOCl and ClO2 provided 73.9% and 72.6% bacterial inactivation after 20 min of treatment. The rapid increment at conductivity and lipid peroxidation within 30 s of treatment indicates that EAW causes membrane damage much more expeditiously compared to other disinfectants. DNA and protein leakage increased gradually during the treatment with EAW and reached 44.9 and 5.8 mu g/ml, respectively. All disinfectants were found as inactivating the bacteria by disrupting cell membrane integrity, unbalancing the ion concentration and damaging the cellular components such as DNA, protein, lipid molecules. It is considered that EAW is more effective due to its superior content including chlorine dioxide, free radicals and ozone besides hypochlorous acid.