Antimicrobial efficacy of nanosilver, sodium hypochlorite and chlorhexidine gluconate against Enterococcus faecalis

The purpose of this study was to compare the antibacterial efficacy of nanosilver (NS), chlorhexidine gluconate (CHX) and sodium hypochlorite (NaOCl) against Enterococcus faecalis. Two tests of minimum inhibitory concentration (MIC) and zone of inhibition were carried out using NS, NaOCl and CHX. 70-fold concentration of NaOCl is required for the same antibacterial effect of NS. CHX precipitated in contact with the culture medium and was excluded from MIC test. The means and standard deviations of the zones of inhibition for 5.25% NaOCl, 0.33% NaOCl, 25 μg/ml NS, 50 μg/ml NS, 4000 μg/ml NS and 2% CHX were 12.16 ± 1.46, 6.91 ± 0.66, 10.00 ± 0.42, 12.00 ± 0.60, 13.33 ± 1.23 and 24.80 ± 1.11, respectively. Statistical analysis using ANOVA showed significant differences among groups (p < 0.001). A post hoc Tukey test revealed no significant differences between 5.25% NaOCl and 4000 μg/ml NS (p = 0.057). However, the zones of inhibition for 2% CHX were significantly larger than those seen around the filter papers saturated with undiluted NaOCl and NS (p < 0.001 for both). This study revealed that NS in a remarkably lower concentration would possess the same bactericidal effect as 5.25% NaOCl.Key words: Chlorhexidine gluconate, Enterococcus faecalis, nanosilver, sodium hypochlorite