Antimicrobial activity of magainin analogues against anaerobic oral pathogens

Magainins are a family of potent antimicrobial cationic peptides that possess antimicrobial activity against a wide range of target organisms. In this study, the antimicrobial activity of synthetic magainin-mimetic compounds MSI-751 and MSI-774 was investigated against the periodontal pathogens Porphyromonas gingivalis, Fusobacterium nucleatum, Actinobacillus actinomycetemcomitans, Eikenella corrodens, Prevotella loescheii and Prevotella intermedia. P. gingivalis was more susceptible to MSI-751 than to MSI-774, whereas the other oral pathogens showed little difference in susceptibility to the two compounds. MSI-751 exhibited a rapid, dose-dependent bactericidal effect on P. gingivalis. Electron microscopy of MSI-751-treated P. gingivalis revealed intact cell wall vesicles devoid of cell contents, suggesting perturbation of the cytoplasmic membrane by this compound, perhaps equivalent to formation of membrane-disruptive ion channels by magainin peptides. These studies demonstrate that synthetic magainin derivatives exhibit antimicrobial activity against oral pathogens by disruption of cell membrane integrity.