Adherence of Streptococcus salivarius HB and HB-7 to oral surfaces and saliva-coated hydroxyapatite.

We compared the binding of Streptococcus salivarius HB and the mutant HB-7 to oral surfaces in vivo. Mutant HB-7 does not aggregate with saliva nor does it bind to buccal epithelium, but it does retain its ability to coaggregate with Veillonella and Fusobacterium. At 1 h after inoculation into the oral cavity of six volunteers, significantly more S. salivarius HB than HB-7 cells were found adhering to the buccal mucosa (P < 0.05) and to a cleaned tooth surface (P < 0.01); there was no significant difference in the numbers adhering to the tongue. The ratio of HB to HB-7 on the tongue increased in samples taken 1, 3, and 9 days after inoculation. The average time required to clear the mutant HB-7 from the oral cavity was 7 days, whereas that for the parent HB was greater than 20 days, and in some cases strain HB was still present 3 months after its inoculation. A representative S. salivarius serotype II strain, designated T3, behaved similarly to mutant HB-7 with respect to its adherence to the buccal mucosa. Strain HB adhered better to hydroxyapatite treated with human saliva than mutant HB-7; both strains adhered in similar numbers to untreated hydroxyapatite. Hydroxyapatite treated with rat saliva bound less HB than hydroxyapatite treated with human saliva, corresponding to the lower aggregating activity of rat saliva. Extraction of saliva with aggregating strains of S. salivarius reduced the ability of saliva to mediate attachment of strain HB to hydroxyapatite.