Attachment of Streptococcus gordonii HG 222 to Streptococcus oralis Ny 586 and the Influence of Saliva

Abstract

The binding of Streptococcus gordonii HG 222 to other streptococci was tested by coaggregation and by binding to immobilised bacteria in an ELISA assay. Out of 17 streptococcal strains, HG 222 coaggregated only with Streptococcus sanguis HG 1470 and Streptococcus oralis Ny 586. Binding of HG 222 to immobilised bacteria also occurred only with HG 1470 and NY 586. Binding of HG 222 to S. oralis Ny 586 was further investigated.

Preincubation of Ny 586 coated microtitreplates with whole saliva, parotid, submandibular and sublingual saliva enhanced binding of HG 222 to Ny 586. Several salivary substances bound to both HG 222 and Ny 586, namely low molecular weight mucins, salivary agglutinin, and IgA.

There were indications that binding of HG 222 to Ny 586 was especially enhanced by IgA. Binding of IgA to both bacteria could be demonstrated with all the types of glandular saliva. In addition, purified colostral IgA enhanced binding of HG 222 to Ny 586. Saliva preincubation of Ny 586 coated microtitreplates in the presence of antiserum against the IgA a-chain inhibited saliva mediated binding of HG 222 to Ny 586. In this case, binding of salivary agglutinin to Ny 586 was also inhibited, suggesting complexation between IgA and agglutinin.

In conclusion, these results indicate that colonisation of dental surfaces by S. gordonii may be accomplished by binding to strains of S. oralis or 5. sanguis. This process may be enhanced by IgA in saliva.

Key Words:

• oral streptococci
• saliva
• coaggregation
• interbacterial binding