Effect of crevicular fluid and lysosomal enzymes on the adherence of streptococci and bacteroides to hydroxyapatite

Samples of hydroxyapatite (HA) beads smaller than 1 mg were coated with 10 microliter of either saliva, serum, or human crevicular fluid before being added to a suspension of Streptococcus sanguis or Bacteroides gingivalis. In some assays, preparations of a granular fraction, elastase, or cathepsin G from human leukocytes were used to coat HA or to treat saliva-coated HA (SHA) before mixing with bacteria. The number of cells adhering to the beads was then counted under a scanning electron microscope by a standardized procedure. More cells were found to adhere to SHA in this assay than in the conventional large-scale assay. Human crevicular fluid, even when diluted up to three times, completely inhibited the adherence of S. sanguis to HA. A 100% inhibition of S. sanguis adherence was also observed when HA was coated with the granular fraction of leukocytes, and a 65% inhibition observed when SHA was treated with the enzyme preparation. When used to coat HA, elastase and cathepsin G reduced the adherence of S. sanguis by 30 and 50%, respectively. The binding of S. sanguis to elastase- or cathepsin G-treated SHA was also reduced. B. gingivalis 33277 was found to adhere in high numbers to SHA. Coating HA with crevicular fluid or with the lysosomal enzyme preparation had a limited negative effect. We postulate that crevicular fluid prevents the adherence of S. sanguis by virtue of either its enzyme content or its albumin content or both.