Abstract
This study investigated the role of extracellular deoxyribonucleic acid (eDNA) on Enterococcus faecalis ( E. faecalis ) biofilm and the susceptibility of E. faecalis to sodium hypochlorite (NaOCl). E. faecalis biofilm was formed in bovine tooth specimens and the biofilm was cultured with or without deoxyribonuclease (DNase), an inhibitor of eDNA. Then, the role of eDNA in E. faecalis growth and biofilm formation was investigated using colony forming unit (CFUs) counting, eDNA level assay, crystal violet staining, confocal laser scanning microscopy, and scanning electron microscopy. The susceptibility of E. faecalis biofilm to low (0.5%) or high (5%) NaOCl concentrations was also analyzed by CFU counting. CFUs and biofilm formation decreased significantly with DNase treatment (p<0.05). The microstructure of DNase-treated biofilms exhibited less structured features when compared to the control. The volume of exopolysaccharides in the DNase-treated biofilm was significantly lower than that of control (p<0.05). Moreover, the CFUs, eDNA level, biofilm formation, and exopolysaccharides volume were lower when the biofilm was treated with DNase de novo when compared to when DNase was applied to matured biofilm (p<0.05). E. faecalis in the biofilm was more susceptible to NaOCl when it was cultured with DNase (p<0.05). Furthermore, 0.5% NaOCl combined with DNase treatment was as efficient as 5% NaOCl alone regarding susceptibility (p>0.05). Inhibition of eDNA leads to decrease of E. faecalis biofilm formation and increase of susceptibility of E. faecalis to NaOCl even at low concentrations. Therefore, our results suggest that inhibition of eDNA would be beneficial in facilitating the efficacy of NaOCl and reducing its concentration.
Highlights
This study investigated the role of extracellular deoxyribonucleic acid on Enterococcus faecalis (E. faecalis) biofilm and the susceptibility of E. faecalis to sodium hypochlorite (NaOCl)
The DNase-2d group showed fewer Colony forming unit (CFU) when compared to the DNase1h group (p
A recent study reported that DNase treatment does not disperse 24-hour matured E. faecalis biofilms formed in root canal systems
Summary
Enterococcus faecalis (E. faecalis) is a bacterium frequently recovered from infected root canal systems. This bacteria is difficult to remove since it is able to form biofilms and survive under a wide range of acidic and basic conditions and prolonged periods of nutritional deprivation. E. faecalis biofilms consist of exopolysaccharides, proteins, lipids, and extracellular deoxyribonucleic acid (eDNA). The dense and protected environment of a biofilm may facilitate gene transfer and enhance biofilm stability. As a major structural component of many different microbial biofilms, the importance of eDNA was first reported in Pseudomonas aeruginosa. The eDNA is released via autolysis in a fratricidal or suicidal manner and/or active release through membrane vesicles and nanofibers in E. faecalis biofilms. Previous reports have attributed a crucial role to eDNA in the formation, mechanical stability, and maturation of bacterial biofilms in general and E. faecalis biofilms in particular. Irrigation is critical to remove microorganisms from root canal systems. Enterococcus faecalis (E. faecalis) is a bacterium frequently recovered from infected root canal systems.. Enterococcus faecalis (E. faecalis) is a bacterium frequently recovered from infected root canal systems.1,2 This bacteria is difficult to remove since it is able to form biofilms and survive under a wide range of acidic and basic conditions and prolonged periods of nutritional deprivation.. It is assumed that a higher concentration of NaOCl increases the efficacy in removing bacteria within root canal systems; severe complications of NaOCl extrusion during endodontic treatment can occur at high concentrations.. Since eDNA is an essential component of E. faecalis biofilm, it can be speculated that its inhibition using a simple agent can be another strategy for effective biofilm removal. The aim of this study was to investigate the role of eDNA in the formation of E. faecalis biofilm in bovine root canal systems through
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