Redundancy refers to the observation that many salivary proteins exhibit similar properties in vitro. It is possible that bacterial adherence to salivary pellicle occurs as a cumulative effect of multiple proteins. This study determined the joint and individual contributions of salivary amylase, S-IgA, lysozyme, salivary peroxidase, lactoferrin, and total protein concentrations to adherence by oral viridans streptococci in microplates coated with whole saliva from 123 persons. Strains used were: Streptococcus gordonii Blackburn, 10558, Streptococcus mitis 10712, 903, Streptococcus oralis 10557, 9811, and Streptococcus sanguis 10556, 13379. Rabbit antibody against 13379 was used for the detection of adherence. This antibody cross-reacted with all strains. Absorbance was standardized against saliva pooled from five donors. All saliva samples had been previously assayed for amylase, lactoferrin, lysozyme, secretory IgA, peroxidase, and total protein. Adherence scores for all strains except 13379 were significantly and positively correlated. Salivas binding high or low levels of one strain tended to bind others correspondingly. Multiple regression indicated significant contributions to 10558 adherence from total protein and lactoferrin (positive), and peroxidase and lysozyme (negative). Similar results were obtained for Blackburn and 903. Significant individual correlations were seen for 9811 and total protein (positive), 10557 and peroxidase (negative), and 13379 and lactoferrin (negative). Salivas with high adherence scores contained significantly more protein and lactoferrin, and significantly less peroxidase, than salivas with low adherence scores. These findings support the hypothesis that multiple proteins contribute to the adherence of streptococcal strains in vivo.

This paper reports a system for measuring saliva protein binding to oral streptococci. Enamel chips with layers of Streptococcus gordonii Blackburn or Streptococcus oralis 10557 were incubated in vitro with whole saliva from eight persons. Blackburn bound significantly more amylase than 10557; no strain differences were seen for lysozyme or lactoferrin. There were significant correlations between saliva and bound amylase and lactoferrin. Blackburn and 10557 chips were then placed in ten subjects. Sites included the buccal left and right upper premolars and molars (UL, UR), labial upper central incisors (UC), and lingual lower central incisors (LL). That study was repeated three months later; chips with Streptococcus sanguis 13379 were also placed then. Blackburn bound significantly more amylase than the other strains. Blackburn and 10557 both bound the most amylase at UL and UR, and the least amylase at UC. However, strain 13379 bound less amylase at UL. That strain also bound significantly less sIgA at UL. All three strains bound the least sIgA at UC. Lysozyme and lactoferrin binding showed few differences among sites or strains. Bound protein concentrations were significantly correlated across sites and strains within subjects, but not correlated with whole saliva. Strain differences may reflect species differences in amylase binding, or differences in species-specific sIgA titers. Site differences may indicate local variation in protein availability. Differences between chip correlations with whole saliva in vitro and in vivo suggest that the salivary film may be modified as it flows over tooth surfaces.