Growth inhibition of oral streptococci in saliva by anionic proteins from two caries-free individuals.

Mixed saliva from two caries-free individuals possessed antimicrobial activity toward Streptococcus mutans and S. sanguis. This inhibitory activity was attributed to the presence of a group of four anionic proteins each of which strongly inhibited the growth of the oral streptococci in a saliva protein-based medium but not in a medium containing amino acids as a nitrogen source. These proteins, with isoelectric points of 4.70, 4.90, 4.98, and 5.05, respectively, neither reacted with antisera to immunoglobulin A, G, or M nor appeared to be functionally related to a number of salivary peroxidases, lactoferrin, or lysozyme. On this basis, they may represent a previously unreported group of growth-inhibitory antimicrobial factors occurring in the saliva of some individuals.