title: Bacterial internalization in periodontitis.
abstract: BACKGROUND
  Bacterial invasion of host epithelial cells plays an important role in the pathogenesis of periodontitis; however, the exact mechanism of the invasion has not been investigated.
  
  
  METHODS
  Pocket epithelium biopsies in periodontitis were analysed via scanning and transmission electron microscopy using ultra-histochemical staining with ruthenium red for glycocalyx visualization.
  
  
  RESULTS
  We demonstrated that oral bacteria adhered via fimbriae-mediated adhesion only. The bacterial internalization in periodontitis was marked by the hallmark of the fimbriae-induced zipper mechanism--the phagocytic cup formation--but we found no sign of the trigger mechanism of internalization. In addition, we frequently observed apoptosis in the phagocytizing epithelial cells.
  
  
  CONCLUSIONS
  Fimbriae-mediated adhesion is a prerequisite for bacterial invasion in periodontitis. This occurs by the fimbriae-induced zipper mechanism of internalization. As internalization induces apoptosis, the subsequent exfoliation might play a significant role in the clearance of periodontal pathogens.
authors.affiliation: Department of Operative Dentistry and Periodontology, Saarland University, Germany. lvitkov@yahoo.com
authors.forename: L
authors.initials: L
authors.lastname: Vitkov
authors.forename: W D
authors.initials: WD
authors.lastname: Krautgartner
authors.forename: M
authors.initials: M
authors.lastname: Hannig
mesh_terms: D017209:Apoptosis / Q000502:physiology; D001419:Bacteria / Q000648:ultrastructure; D001422:Bacterial Adhesion; D018407:Bacterial Physiological Phenomena; D004396:Coloring Agents; D004847:Epithelial Cells / Q000382:microbiology / Q000648:ultrastructure; D010861:Fimbriae, Bacterial / Q000502:physiology / Q000648:ultrastructure; D005881:Gingiva / Q000382:microbiology* / Q000648:ultrastructure; D019276:Glycocalyx / Q000648:ultrastructure; D006801:Humans; D008855:Microscopy, Electron, Scanning; D046529:Microscopy, Electron, Transmission; D008875:Middle Aged; D010514:Periodontal Pocket / Q000382:microbiology; D010518:Periodontitis / Q000382:microbiology*; D010587:Phagocytosis / Q000502:physiology; D012430:Ruthenium Red
chemical_list: D004396:Coloring Agents; D012430:Ruthenium Red