Characterization of Antimicrobial Peptides as Potential Agents Against Oral Bacteria

Introduction: Bacteria, present in biofilms in the oral cavity, are the primary pathogens associated with dental diseases. Use of antibacterial peptides can overcome some of the side effects associated with chemical antibacterial agents. Objectives: To characterize the activity of several peptides against oral bacterial pathogens in planktonic and biofilm conditions. Materials and methods: Three peptides were tested: LL37, a member of the cathelicidin family naturally found in the oral cavity; K4-S4(1-15)a, an analog of dermaseptin S4, originally isolated from frog skin; and Dhvar4, an analog of histatin-5, which is secreted from salivary glands. Chlorhexidine digluconate served as positive control in all experiments. Minimal inhibitory concentration was determined using a microdilution assay. The biofilm killing effect was evaluated using confocal laser scanning microscopy (CSLM). Stability of the peptides was assessed by gel electrophoresis followed by Western blot analysis. Results: LL37 was found to be poorly active against the oral streptococci and A. viscosus. In contrast, Dhvar4 exhibited higher potency towards the gram positive oral bacteria compared to the tested gram negative oral bacteria. K4-S4(1-15)a was equally potent towards species tested, except for P. gingivalis (Pg) and A. actinomycetemcomitans (Aa). Aa demonstrated lower susceptibility towards the peptides tested compared to other species. LL37 and K4-S4(1-15)a had no effects on growth of Pg, and LL37 was found to undergo rapid degradation in the supernatant fluid of Pg. Incubation of immobilized S. mutans as well as S. mutans biofilms in the presence of sucrose and K4-S4(1-15)a, inhibited biofilm growth. Conclusion: Our results support growing evidence indicating the relevance of antibacterial peptides as potential pharmaceutical tools in coping with oral disease. This study is supported in part by the GSK/IADR award.