Comparisons of the killing effect of direct current partially mediated by reactive oxygen species on and in planktonic state and biofilm state - an study.

BACKGROUND/PURPOSE: Bacterial biofilms formed on the surface of tissues and biomaterials are major causes of chronic infections in humans. Among them, () and () are anaerobic pathogens causing dental infections associated with periodontitis. In this study, we evaluated the killing effect and underlying mechanisms of direct current (DC) as an antimicrobial method .

MATERIALS AND METHODS

We chose and in different states to make comparisons of the killing effect of DC. By viable bacteria counting, fluorescent live/dead staining, reactive oxygen species (ROS) assay, addition of ROS scavenger DMTU and mRNA expression assay of ROS scavenging genes, the role of ROS in the killing effect was explored.

RESULTS

The planktonic and biofilm states of two bacteria could be effectively killed by low-intensity DC. For the killing effect of 1000 μA DC, there were significant differences whether on planktonic and (mean killing values: 2.40 vs 2.62 log CFU/mL) or on biofilm state of those (mean killing values: 0.63 vs 0.98 log CFU/mL). 1000 μA DC greatly induced ROS production and the mRNA expression of ROS scavenging genes. DMTU could partially decrease the killing values of DC and downregulate corresponding gene's expression.

CONCLUSION

1000 μA DC can kill and in two states by promoting overproduction of ROS, and is more sensitive to DC than . These findings indicate low-intensity DC may be a promising approach in treating periodontal infections.