Inhibition of Lactose-Reversible Adherence between Actinomyces viscosus and Oral Streptococci by Salivary Components

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Abstract
The influence of saliva on lactose-reversible adherence between strains of Actinomyces viscosus and Streptococcus sanguis or Streptococcus mitis was investigated. Because saliva agglutinated these organisms, it was necessary to develop models for studying streptococcal attachment to Actinomyces cells which did not depend upon mixed agglutination of both interacting organisms. One model involved the binding of radiolabelled streptococci to spermine-conjugated agarose beads coated with Actinomyces. This assay appeared to parallel previously described coaggregation reactions because coaggregation-positive streptococcal strains attached in much higher numbers to the Actinomyces-coated beads than did coaggregation-negative strains. Lactose and also saliva which had been depleted of streptococcal agglutinins strongly inhibited attachment of coaggregation-positive organisms. A second model involved use of sonic extracts of Actinomyces cells which agglutinated coaggregation-positive streptococcal strains, but not coaggregation-negative strains. This extract-induced streptococcal agglutination was also inhibited by lactose and by saliva samples collected from 6 donors representative of blood types A, B, and O.