Enhanced Attachment of Porphyromonas gingivalis to Human Fibroblasts Mediated by Fusobacterium nucleatum

Fusobacterium nucleatum and Porphyromonas gingivalis are often co-isolated from endodontic infection sites. The present study tested the hypothesis that adhesin-mediated reactions might contribute to this phenomenon. F. nucleaum PK1594 and P. gingivalis PK1924 were selectively labeled with fluorochromes and allowed to adhere to human fibroblasts, either each strain alone or sequentially. The number of bacteria of each type adhering to individual fibroblasts was determined. Sugar inhibition profile of this adherence was explored. Attachment of P. gingivalis to human fibroblasts increased by nearly 10-fold when F. nucleatum was present (P < .001). Galactose, lactose, and fucose inhibited this enhanced attachment (P < .001), as well as that of F. nucleatum alone (P < .001). The results suggest that F. nucleatum might be a primary colonizer of the host tissues and serve as mediator for enhanced attachment of P. gingivalis to the host cells. This might explain in part the common co-occurrence of F. nucleatum and P. gingivalis in endodontic mixed infections.