In vitro assessment of antimicrobial peptides as potential agents against several oral bacteria

Background: Antimicrobial peptides are components of the innate immunity that play an important role in systemic and oral health. Objectives: The antibacterial activity of the amphibian-derived K₄-S4(1-15)a antimicrobial peptide was tested against oral pathogens associated with caries and periodontitis and compared with the activities of the human-derived antimicrobial peptides LL-37 and dhvar4a. Methods: Growth inhibition of planktonic bacteria was tested using standard microdilution assays. Live/Dead staining followed by confocal scanning laser microscopy (CSLM) was used to determine the bactericidal effect of K₄-S4(1-15)a on Streptococcus mutans attached to a glass surface or grown as biofilm. Results: The cariogenic species S. mutans, Streptococcus sobrinus, Lactobacillus paracasei and Actinomyces viscosus were resistant to LL-37 found in the oral cavity. Porphyromonas gingivalis was the species most resistant to the three tested peptides. K₄-S4(1-15)a demonstrated the highest activity against the tested planktonic bacteria. In addition, K₄-S4(1-15)a was bactericidal to surface-attached S. mutans as well as to S. mutans biofilms grown in vitro. However, surface attachment increased S. mutans resistance to the antimicrobial peptide. Conclusions: Our results support growing evidence suggesting the use of antimicrobial peptides for prevention and treatment of oral disease.