title: Infection of human gingival fibroblasts with Aggregatibacter actinomycetemcomitans: An in vitro study.
abstract: OBJECTIVE
  Aggregatibacter actinomycetemcomitans is known to be a major cause of localized aggressive periodontitis. Previous research has suggested that A. actinomycetemcomitans can damage many types of host cells. There is evidence for the ability of this organism to invade endothelial and epithelial cells, but information pertaining to its potential for invading gingival fibroblasts is very limited. Internalization of bacteria is not only responsible for damaging host tissue but also a means to evade the host immune response. It was hypothesized that A. actinomycetemcomitans can invade and reside in human gingival fibroblasts (HGF).
  
  
  METHODS
  Primary cultures of HGF were infected with A. actinomycetemcomitans at a ratio of 1:100. Bacterial internalization was determined by an antibiotic protection assay. Bacterial-fibroblast interaction was examined using phase-contrast, scanning and transmission electron microscopy.
  
  
  RESULTS
  It was demonstrated that A. actinomycetemcomitans was internalized into HGF at an efficiency of 0.084%. Transmission electron microscopic study showed the presence of A. actinomycetemcomitans in the cytoplasm of HGF without the surrounding membrane. Scanning electron micrographs revealed the sloughing of HGF surfaces on which A. actinomycetemcomitans adhered. Rounded cells, attachment loss and damaged cells were also observed.
  
  
  CONCLUSIONS
  It is concluded that the attachment and invasion of A. actinomycetemcomitans into human gingival fibroblasts play a role in periodontal tissue damage and may also be a means of immune evasion.
authors.affiliation: Department of Oral Medicine, Faculty of Dentistry, Chulalongkorn University, Bangkok, Thailand. Pratanporn.A@chula.ac.th
authors.forename: Pratanporn
authors.initials: P
authors.lastname: Arirachakaran
authors.forename: Wandee
authors.initials: W
authors.lastname: Apinhasmit
authors.forename: Proudchompoo
authors.initials: P
authors.lastname: Paungmalit
authors.forename: Pawika
authors.initials: P
authors.lastname: Jeramethakul
authors.forename: Pimprapa
authors.initials: P
authors.lastname: Rerkyen
authors.forename: Rangsini
authors.initials: R
authors.lastname: Mahanonda
mesh_terms: D000189:Actinobacillus Infections / Q000473:pathology / Q000503:physiopathology*; D016976:Aggregatibacter actinomycetemcomitans / Q000472:pathogenicity*; D010520:Aggressive Periodontitis / Q000209:etiology*; D002478:Cells, Cultured; D005347:Fibroblasts / Q000276:immunology / Q000382:microbiology* / Q000648:ultrastructure; D005881:Gingiva / Q000276:immunology / Q000382:microbiology* / Q000473:pathology; D006801:Humans; D008855:Microscopy, Electron, Scanning; D046529:Microscopy, Electron, Transmission; D008858:Microscopy, Phase-Contrast