Adherence of Porphyromonas (Bacteroides) gingivalis to Streptococcus sanguis in vitro

Abstract

Intergeneric bacterial adherence is responsible for the complexity of the microbiota in human dental plaque and is believed to enable some extraneous bacteria to initially colonize the human oral cavity. Some current evidence indicates that Streptococcus sanguis, an early colonizer of teeth, enhances subsequent colonization by Porphyromonas (Bacteroides) gingivalis, a bacterium associated with advanced adult periodontitis. In this study, selected strains of P. gingivalis and S. sanguis were tested for their adherence activities in vitro. A differential filtration assay was devised in which one member of the test pair was radiolabeled. Heterogeneous aggregates that formed in mixed suspensions were collected on polycarbonate filters (8-,um pore size) and were washed free of individual bacteria and small homologous clumps. P. gingivalis 381, W50, JKG7, and 33277 adhered to S. sanguis G9B, M5, Challis 6, and 38. P. gingivalis A7A1-28 did not adhere well to S. sanguis under these conditions. More precise measurements of intergeneric adherence were obtained with an alternative assay with radiolabeled P. gingivalis and an artificial dental plaque composed of S. sanguis coupled to cyanogen bromide-activated agarose beads. CNBr-agarose was selected as the supporting matrix for the plaque because it was uniformly and permanently coated with S. sanguis and because P. gingivalis had negligible adherence activity for streptococcus-free beads. P. gingivalis W50 grown to the early stationary phase adhered to S. sanguis-coated beads in higher numbers than either midlogarithmicor late-stationary-phase cells. Intergeneric adherence was not inhibited or reversed by the presence of lactose or other monosaccharides or disaccharides. Pretreatment of either bacterium with trypsin or proteinase K reduced subsequent adherence by 86 to 100%. Neuraminidase treatment of P. gingivalis caused 98% reduction of adherence, whereas similar treatment of S. sanguis caused only a 2% loss. Preincubation of P. gingivalis at 60C for 30 min decreased subsequent adherence to S. sanguis-coated beads by 94%. Adherence was reduced by 96% when bacteria were assayed while suspended in human whole saliva or when pretreated with saliva and subsequently assayed in buffer. The concentration of whole human saliva required to inhibit 50% adherence in this assay was 23 ,ug per ml (1:200 dilution). Suspension of the bacteria in normal rabbit serum resulted in 94% inhibition of adherence. These data indicate that saliva and serum may be important host defense factors for controlling Porphyromonas-Streptococcus adherence.

Involvement of Porphyromonas gingivalis fimbriae in adherence to Streptococcus gordonii

“…Many of the organistns that cotnprise plaque possess the ability to adhere to other species, which is considered to be a tnajor detertninant of bacterial colonization (11,26). P. gingivalis, an itnportant periodontal pathogen, can adhere to antecedent plaque organistns such as A. viscosus and sanguis group streptoeocci (14,25,30). P. gingivatis fitnbriae have been implicated in adherence to A. vi.seosus (6); however, the tnolecules that mediate binding to sanguis group organisms such as S. gordonii have not been detertnined.…”

“…The mechanisms by which P. gingivalis colonizes the oral cavity are complex and involve adherence to oral surfaces such as preformed plaque. P. gingivalis can adhere to a variety of plaque bacteria, including sanguis group streptococci such as Slreptocociis gordonii (14,30), Actinomyees viseosus (25) and Fusobacterium nucleatum (10,12). The importance of this interbacterial binding has been demonstrated in vivo by studies showing the selective colonization of P. gingivalis in areas where preformed bacterial plaque was present (26).…”

The road less traveled – defining molecular commensalism with Streptococcus sanguinis

“…A variety of S. sanguinis coaggregation partners have been identified including species of Actinomyces, Prevotella, and Porphyromonas (originally grouped in the genus Bacteroides), Capnocytophaga, Fusobacterium, and Candida (Jenkinson et al, 1990). Porphyromonas gingivalis was shown to adhere to S. sanguinis (Stinson et al, 1991;Lamont et al, 1992) via a surfaceexposed glyceraldehyde-3-phosphate dehydrogenase (GAPDH) (Maeda et al, 2004). Given the pathogenic potential of P. gingivalis, S. sanguinis might have measures in place to limit the overgrowth of P. gingivalis and other potentially damaging coaggregation partners via its aforementioned H 2 O 2 production ability and perhaps other uncharacterized mechanisms as well.…”

Controlling plaque by disrupting the process of plaque formation

“…Protein-protein interactions are also possible, such as between I! gingivulis and S. sunguis, as demonstrated by the inhibition of coaggregation using saliva and protease treatments (71). The characterization of these specific coaggregation interactions should allow the development of analogues or inhibitors capable of disrupting these processes.…”