Modelling the Gingival Pocket by Enrichment of Subgingival Microflora in Human Serum in Chemostats

Abstract

This study was undertaken to design a relevant model system with conditions resembling the gingival pocket, in order to identify ecological factors that stimulate the establishment and maintenance of pathogenic subgingival microflora. Human serum as a substitute for gingival exudate was used in continuous culture enrichments of subgingival plaque to enable the selection of slow-growing (D≅0.08 h−1) consortia of microorganisms. After one week of continuous cultivation, species such as Treponema denticola, Peptostreptococcus spp., Lactobacillus catenaforme, Streptococcus spp., Bacteroides spp., Eubacterium spp. and Veillonella parvula became the predominating organisms. The cultures produced a wide variety of mainly cell-bound hydrolytic enzymes which have been associated with periodontal disease. The consortia preferentially consumed carbohydrates as was also indicated by the altered electrophoretic mobility of the serum glycoproteins due to removal of carbohydrate side-chains. Extensive degradation of glycoproteins such as immunoglobulins, haptoglobin, transferrin and α1-antitrypsin was observed. Acetic, butyric and propionic acids were the major products of metabolism suggesting heterolactic fermentation and amino acid catabolism. These products are typical of acidogenesis in anaerobic fermentations. Our results suggest that this in-vitro model can approximate conditions in gingival pockets.