SUPERNATANT CYTOTOXICITY AND PROTEOLYTIC ACTIVITY OF SELECTED ORAL BACTERIA AGAINST HUMAN GINGIVAL FIBROBLASTS IN-VITRO

The purpose of this study was to determine if endodontic bacterial act in vitro on human gingival fibroblast functions via extracellular pro ducts. The bacteria used were Prevotella nigrescens, Capnocytophaga oc hracea, Peptostreptoccocus micros and Actinobacillus actinomycetemcomi tans. Supernatants were collected from bacterial cultures at the begin ning of the stationary phase when their density was similar. Toxins th at inhibited fibroblast proliferation were found in all culture supern atants of Gram-positive or Gram-negative bacterial strains, except for Prev. nigrescens. The cytotoxicity of A. actinomycetemcomitans supern atant was about 1000 fold higher than the others. This super natant di luted to 1/1000 led to total fibroblast growth inhibition whereas only 25% growth inhibition was obtained with Capn. ochracea and Pept. micr os diluted to 1/10. Bacterial supernatant proteolytic activity was inv estigated in confluent fibroblast cultures that were incubated for Is hr with each of the supernatants diluted to 1/2 except for A. actinomy cetemcomitans supernatant diluted to 1/20. Indirect immunofluorescence studies of extracellular-matrix molecules, followed by immunoelectrop horetic analysis of extracts of whole-cell layers, demonstrated that o nly conditioned medium of Prev, nigrescens had a proteolytic activity capable of degrading the greater part of type I collagen and fibronect in fibres in the extracellular matrix. (C) 1998 Elsevier Science Ltd. All rights reserved.