Effects of metronidazole on Porphyromonas gingivalis biofilms

J Periodontal Res. 1997 Jul;32(5):473-7. doi: 10.1111/j.1600-0765.1997.tb00560.x.


Subgingival bacteria exist within a biofilm consisting of cells and extracellular matrix which may afford organisms protection from both antibiotics and components of the host immune system. MIC values for planktonic Porphyromonas gingivalis treated with metronidazole were compared with those obtained for the same strain in biofilms associated with hydroxyapatite (HA) surfaces. The treated biofilms were examined for growth and studied by scanning electron microscopy. A broth assay resulted in an MIC of 0.125 microgram/ml for metronidazole against P. gingivalis, P. gingivalis biofilms exhibited growth after treatment with 20 micrograms/ml metronidazole, which was 160 times the MIC for planktonic organisms. The results of this study indicate that biofilm-associated P. gingivalis may be resistant to metronidazole at concentrations which are usually attained by systemic administration.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Anti-Bacterial Agents / administration & dosage
  • Anti-Bacterial Agents / pharmacology*
  • Biofilms / drug effects*
  • Biofilms / growth & development
  • Culture Media
  • Drug Resistance, Microbial
  • Durapatite
  • Extracellular Matrix / drug effects
  • Gingiva / immunology
  • Gingiva / microbiology
  • Humans
  • Metronidazole / administration & dosage
  • Metronidazole / pharmacology*
  • Microscopy, Electron, Scanning
  • Porphyromonas gingivalis / drug effects*
  • Porphyromonas gingivalis / physiology
  • Porphyromonas gingivalis / ultrastructure


  • Anti-Bacterial Agents
  • Culture Media
  • Metronidazole
  • Durapatite