Colonization of the subgingival area by Bacteroides gingivalis.

The initial event in colonization of the subgingival area by B. gingivalis is its attachment to host cells and Gram-positive bacteria in pre-formed plaque. The level of B. gingivalis is partly governed by products of other plaque bacteria, especially by sanguicin. Once B. gingivalis resides in its nidus and starts to proliferate, expulsion of pre-existing residents may occur, especially of attached Gram-positive bacteria, through the inhibitory action of the B. gingivalis product, hematin. The bacteriocin produced by black-pigmented Bacteroides also seems to play an important role in their establishment. Melaninogenicus possessed strong inhibitory activity against Actinomyces species. This was not completely confirmed with fresh isolates of B. gingivalis from advanced periodontitis patients. Various factors other than inhibitory substances produced by B. gingivalis and related bacteria can also affect the colonization of this species. Since the crevice area is influenced by gingival fluid, the nature of specific antibody and the other affecting components should be considered collectively with the interaction between new predominant colonizers and other pre-existing residents.