Susceptibilities of periodontopathogenic and cariogenic bacteria to antibacterial peptides, β-defensins and LL37, produced by human epithelial cells

Objectives: Antimicrobial peptides are one of the factors involved in innate immunity. The susceptibility of periodontopathogenic and cariogenic bacteria to the major antimicrobial peptides produced by epithelia was investigated. Methods: Synthetic antimicrobial peptides of human beta-defensin-1 (hBD1), hBD2, hBD3 and LL37 (CAP18) were evaluated for their antimicrobial activity against oral bacteria. They included Actinobacillus actinomycetemcomitans (20 strains), Porphyromonas gingivalis (6), Prevotella intermedia (7), Fusobacterium nucieatum (7), Streptococcus mutans (5), Streptococcus sobrinus (5), Streptococcus salivarius (5), Streptococcus sanguis (4), Streptococcus mitis (2) and Lactobacillus casei (1). Results: Although the four peptides had bactericidal activity against all bacteria tested, the degree of antibacterial activity was variable against the different strains and species. The antibacterial activity of hBD1 was lower than that of the other peptides. Among the bacteria tested in this study, F. nucleatum was highly susceptible to hBD3 and LL37, and S. mutans was highly susceptible to hBD3. We measured the Zeta-potential, representing the net charge of whole bacteria, to study the relationship between susceptibility to cationic peptide and the net charge of the bacteria. Although we found some correlation in A. actinomycetemcomitans strains, we did not find a definite correlation with all the bacterial species. Conclusions: These results indicate that beta-defensins and LL37 have versatile antibacterial activity against oral bacteria.