ABSTRACTProteins in human saliva are thought to modulate bacterial colonization of the oral cavity. Yet, information is sparse on how salivary proteins interact with systemic pathogens that transiently or permanently colonize the oral environment.Staphylococcus aureusis a pathogen that frequently colonizes the oral cavity and can cause respiratory disease in hospitalized patients at risk. Here, we investigated salivary protein binding to this organism upon exposure to saliva as a first step toward understanding the mechanism by which the organism can colonize the oral cavity of vulnerable patients. By using fluorescently labeled saliva and proteomic techniques, we demonstrated selective binding of major salivary components byS. aureusto include DMBT1gp-340, mucin-7, secretory component, immunoglobulin A, immunoglobulin G, S100-A9, and lysozyme C. Biofilm-grownS. aureusstrains bound fewer salivary components than in the planctonic state, particularly less salivary immunoglobulins. A corresponding adhesive component on theS. aureussurface responsible for binding salivary immunoglobulins was identified as staphylococcal protein A (SpA). However, SpA did not mediate binding of nonimmunoglobulin components, including mucin-7, indicating the involvement of additional bacterial surface adhesive components. These findings demonstrate that a limited number of salivary proteins, many of which are associated with various aspects of host defense, selectively bind toS. aureusand lead us to propose a possible role of saliva in colonization of the human mouth by this pathogen.
The Prevalence of Staphylococcus aureus in the Oral Cavity of Healthy Adults in Malaysia
