A comparison of the adhesion, coaggregation and cell-surface hydrophobicity properties of fibrillar and fimbriate strains of Streptococcus salivarius

Fibrillar and fimbriate strains of Streptococcus salivarius were compared for their ability to adhere to buccal epithelial cells and saliva-coated hydroxyapatite beads, and for their ability to coaggregate with Veillonella strains. The fibrillar Lancefield group K strains adhered statistically significantly better to both buccal epithelial cells and saliva-coated hydroxyapatite beads than the fimbriate strains, which lacked the Lancefield group K antigen. After 1 h the fibrillar strains coaggregated statistically significantly better than the fimbriate strains with V. parvula strain V1, but after 24 h, coaggregation both of fibrillar and of fimbriate strains reached approximately 90%. Freshly isolated Veillonella strains all coaggregated with the S. salivarius strains, but the percentage coaggregation varied considerably after 1 h depending on the Veillonella strain. Coaggregation was independent of the presence of Ca2+. S. salivarius strain HB-V5, a mutant of strain HB that had lost the Veillonella-binding protein, coaggregated weakly with V. parvula strain V1, but coaggregated very well with other wild-type veillonellae, suggesting the presence of an alternative mechanism for Veillonella-binding for strain HB. Fibrillar strains were, therefore, more adhesive to oral surfaces and coaggregated with veillonellae after 1 h better than the fimbriate S. salivarius strains. Both fibrillar and fimbriate strains were highly hydrophobic in the hexadecane-buffer partition assay.