The study tested three antimicrobial peptides, including the human peptide LL‑37, against common mouth bacteria. LL‑37 didn’t stop most of the tested germs, especially the ones that cause cavities and gum disease. A frog‑derived peptide (K4‑S4(1‑15)a) worked best, even killing bacteria stuck to surfaces or in biofilms, though bacteria become a bit tougher when attached.

Antimicrobial peptides are components of the innate immunity that play an important role in systemic and oral health. 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. 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. 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. Our results support growing evidence suggesting the use of antimicrobial peptides for prevention and treatment of oral disease.