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


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.


CONCLUSIONS
Our results indicate that immune evasion may contribute to the pathogenicity of some periodontopathic bacteria.
Ji
S
S
Program of Oromaxillofacial Infection & Immunity and BK21, School of Dentistry, Seoul National University, Seoul, Korea.
Hyun
J
J
Park
E
E
Lee
B-L
BL
Kim
K-K
KK
Choi
Y
Y
D000190:Actinomyces / Q000187:drug effects / Q000276:immunology; D016976:Aggregatibacter actinomycetemcomitans / Q000187:drug effects / Q000276:immunology; D000890:Anti-Infective Agents / Q000494:pharmacology*; D023181:Antimicrobial Cationic Peptides / Q000494:pharmacology*; D001419:Bacteria / Q000145:classification / Q000187:drug effects* / Q000276:immunology; D001439:Bacteroides / Q000187:drug effects / Q000276:immunology; D024881:Drug Resistance, Bacterial; D016124:Eikenella corrodens / Q000187:drug effects / Q000276:immunology; D005434:Flow Cytometry; D006801:Humans; D008826:Microbial Sensitivity Tests; D009055:Mouth / Q000382:microbiology*; D009504:Neutrophils / Q000502:physiology*; D010510:Periodontal Diseases / Q000382:microbiology; D010587:Phagocytosis / Q000502:physiology*; D016966:Porphyromonas gingivalis / Q000187:drug effects / Q000276:immunology; D018720:Prevotella / Q000187:drug effects / Q000276:immunology; D013291:Streptococcus / Q000187:drug effects / Q000276:immunology; D014678:Veillonella / Q000187:drug effects / Q000276:immunology; D023083:beta-Defensins / Q000494:pharmacology*; D054804:Cathelicidins
D000890:Anti-Infective Agents; D023181:Antimicrobial Cationic Peptides; C422950:DEFB103A protein, human; D023083:beta-Defensins; D054804:Cathelicidins