Attachment of Actinomyces naeslundii to human buccal epithelial cells

A standardized assay was used to measure the attachment of Actinomyces naeslundii ATCC 12104 to washed human buccal epithelial cells. Treatment of the A. naeslundii cells with hyaluronidases, wheat germ lipase, protease, trypsin, heat, or sonic oscillation significantly reduced their ability to attach to epithelial cells. Treatment of the epithelial cells with the above enzymes did not influence the attachment of A. naeslundii. Extraction of A. naeslundii with NaOH also significantly reduced the ability of the bacterium to attach to human buccal epithelial cells. The neutralized and dialyzed NaOH extract contained both carbohydrate and protein substances in a ratio of about 1:1. Adding this extract back to the extracted bacterial cells partially restored their ability to attach to epithelial cells. When the NaOH extract was preincubated with epithelial cells and residual extract was removed by washing, attachment of normal A. naeslundii was partially blocked. The ability of the extracted material to block attachment was significantly reduced when treated with hyaluronidases or with wheat germ lipase. Treatment with heat, protease, or trypsin did not significantly reduce the ability of the extracted materials to block attachment. Pretreatment of the epithelial cells with hyaluronic acid or chondroitin sulfate also reduced subsequent attachment of normal A. naeslundii cells. Pretreatment of epithelial cells with dextrans, proteins, or unpure mannose did not influence subsequent attachment of A. naeslundii. Pretreatment of A. naeslundii with galactose and lactose significantly inhibited attachment to normal epithelial cells. The results suggest that the attachment of A. naeslundii to human buccal epithelial cells may involve mucopolysaccharides similar to hyaluronic acid on the surface of the bacterial cells. Other attachment mechanisms may also be operative.