Antibacterial Effect of the Natural Polymer ε-Polylysine Against Oral Pathogens Associated with Periodontitis and Caries

Antimicrobials are important adjuncts in the treatment of caries and periodontitis. However, increased bacterial resistance and hypersensitivity reactions to commonly used antimicrobials have led to an increasing demand for safe and natural substances. The objective of this study was to investigate the antibacterial effects of epsilon-polylysine against oral pathogensStreptococcus mutansandPorphyromonas gingivalis. Broth dilution assay, scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM) analyses were performed to explore the antibacterial effect of epsilon-polylysine againstS. mutansstrain ATCC25175 andP. gingivalisstrain ATCC332277. For the test solution, epsilon-polylysine was added to the bacterial suspension to prepare 0.125%, 0.25%, 0.5% and 1% epsilon-polylysine solutions diluted in broth medium. All four concentrations demonstrated complete inhibition ofS. mutansand significantly reduced viable cell counts ofP. gingivalisafter 24 h. From starting inoculum of 9.15 log CFU/mL,P. gingivaliscell counts reduced to 4.01 log CFU/mL in the 0.125% epsilon-polylysine treatment group. SEM, CLSM, and the LIVE/DEAD bacterial assay of epsilon-polylysine application onP. gingivalisbiofilm-dentin specimens revealed bacterial cell membrane disruption and irregular cell morphologies. The results indicated satisfactory antibacterial efficacy of epsilon-polylysine againstP. gingivalisandS. mutansin liquid medium and as an application on biofilm-dentin specimens.