Susceptibility of various oral bacteria to antimicrobial peptides and to phagocytosis by neutrophils

J Periodontal Res. 2007 Oct;42(5):410-9. doi: 10.1111/j.1600-0765.2006.00962.x.


Background and objective: The aim of this study was to compare the susceptibility of nonperiodontopathic and periodontopathic bacteria to major defense mechanisms for bacterial clearance in gingival sulcus.

Material and methods: Twenty strains of 13 oral bacterial species were studied for their susceptibility to phagocytosis by human neutrophils and to the antimicrobial peptides LL-37 and human beta defensin-3. The minimum inhibitory concentrations of LL-37 and human beta defensin-3 were determined by a liquid dilution assay, and susceptibility to phagocytosis was examined by a flow cytometric phagocytosis assay.

Results: The minimum inhibitory concentrations of LL-37 and human beta defensin-3 varied greatly, depending on the strain and species. Although a significant difference between the non- and periodontopathic groups was not observed, the red-complex bacteria were more resistant to LL-37 than the others (p=0.004). The susceptibility of oral bacteria to phagocytosis was quite variable, depending on the species but not on the strains. The periodontopathic bacteria, especially Actinobacillus actinomycetemcomitans and the red-complex triad, were more resistant to phagocytosis than were the nonperiodontopathic bacteria (p=0.0003). In addition, bacteria resistant both to antimicrobial peptides and to phagocytosis were more common in the periodontopathic group.

Conclusion: Our results indicate that immune evasion may contribute to the pathogenicity of some periodontopathic bacteria.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Actinomyces / drug effects
  • Actinomyces / immunology
  • Aggregatibacter actinomycetemcomitans / drug effects
  • Aggregatibacter actinomycetemcomitans / immunology
  • Anti-Infective Agents / pharmacology*
  • Antimicrobial Cationic Peptides / pharmacology*
  • Bacteria / classification
  • Bacteria / drug effects*
  • Bacteria / immunology
  • Bacteroides / drug effects
  • Bacteroides / immunology
  • Drug Resistance, Bacterial
  • Eikenella corrodens / drug effects
  • Eikenella corrodens / immunology
  • Flow Cytometry
  • Humans
  • Microbial Sensitivity Tests
  • Mouth / microbiology*
  • Neutrophils / physiology*
  • Periodontal Diseases / microbiology
  • Phagocytosis / physiology*
  • Porphyromonas gingivalis / drug effects
  • Porphyromonas gingivalis / immunology
  • Prevotella / drug effects
  • Prevotella / immunology
  • Streptococcus / drug effects
  • Streptococcus / immunology
  • Veillonella / drug effects
  • Veillonella / immunology
  • beta-Defensins / pharmacology*


  • Anti-Infective Agents
  • Antimicrobial Cationic Peptides
  • DEFB103A protein, human
  • beta-Defensins
  • CAP18 lipopolysaccharide-binding protein