Selective bacterial adherence to oral epithelial surfaces and its role as an ecological determinant

The possible relationship between the ability of Streptococcus species to adhere to oral epithelial cells and their natural distribution on epithelial surfaces within the mouth was studied. Strains of S. salivarius and S. sanguis, which are present in significant proportions on oral epithelial surfaces, were found to possess a definite capacity to adhere to epithelial cells obtained from cheek scrapings of humans, hamsters, and germ-free rats. In contrast, strains of S. mutans, which are found in only minor proportions, if at all, on oral epithelial surfaces exhibited feeble or no adherence to oral epithelial cells. S. salivarius cells attached well to human cheek cells over the range of pH 5 to 8. Its adherence was not found to be markedly influenced by saliva or by growth in sucrose broth. Several other types of bacteria were examined which also exhibited widely different abilities to attach to human cheek cells. Mixtures of streptomycin-labeled strains were introduced into the mouths of volunteers for study of the adherence of Streptococcus species to oral epithelial surfaces in vivo. Labeled S. salivarius and S. sanguis were recovered in high proportions from cheek and tongue surfaces, whereas the proportions of labeled S. mutans recovered from these surfaces were low in comparison to the original mixture. These data indicate that a correlation exists between the relative adherence of various Streptococcus species and their proportional distribution found naturally on oral epithelial surfaces. The ability of bacteria to adhere to surfaces is proposed as a critical ecological determinant affecting their colonization in environments with open surfaces exposed to bathing fluids.