Bacterial adhesion to the soft and hard tissues of the oral cavity

This paper reviews current knowledge of protein‐mediated attachment of oral bacteria to the soft and hard tissues of the oral cavity. In relation to soft tissue attachment, the central role of lectin‐carbohydrate interactions is discussed, together with the potential role of interbacterial coaggregation. The review also presents some current studies on the attachment of strains of Streptococcus oralis, Streptococcus sanguis and Streptococcus mutatis to hydroxyapatite (HA) coated with a range of low molecular weight salivary proteins. The salivary proteins were obtained from human whole saliva by chromatography on Sepharose 4B and further fractionated on DEAE‐Sephacel. Fractions were characterised for protein, carbohydrate and anionic determinants such as sulphate and phosphate. The hydrophobicity of the fractions was determined by their affinity for Octyl‐Sepharose. Selected proteins were attached to HA (20 mg) at a range of concentrations from 20 μg.ml^‐1 to 200 μg.m^‐1. (³H)‐thymidine labelled cells of S. oralis (NCTC 7864) S. sanguis (NCTC 7863) and S. mutans (BHT, D282 and 0MZ61) were mixed with HA in buffered saline and the numbers of bacterial cells adhering were quantitated by radiocounting. The results showed an apparent inverse relationship between anionicity and hydrophobicity of the protein fractions. All the bacteria tested adhered to the protein‐coated HA. The uptake pattern was complex and dependent upon the concentration of the protein coating the HA. In general the highest uptake as a percentage of the untreated HA control featured the least anionic, most hydrophobic fractions. The S. oralis and S. sanguis strains typified this feature most strongly.

Key words:

• Adhesion
• Hydrophobicity
• Lectins
• Oral bacteria
• Salivary proteins