Endocardiac infectivity and binding to extracellular matrix proteins of oral Abiotrophia species

Microorganisms of the genus Abiotrophia, formerly known as nutritionally variant streptococci, are members of the oral flora and often isolated from patients with endocarditis, but pathogenicity of oral Abiotrophia species has not been examined yet. In this study, 17 strains isolated from healthy human oral cavities and 7 reference strains (all derived from patients with endocarditis) of Abiotrophia spp. were tested for their abilities to cause infections in damaged heart tissues in catheterized rats and to adhere to extracellular matrix proteins in vitro. The reference strains of A. defectiva and A. adiacens showed high infectivities in the rats. Four oral isolates of these two species showed similarly high infectivities and three had moderate infectivities. Most of 10 oral strains of A. para-adiacens and A. elegans were found to be generally less infective. The highly infective A. adiacens strains showed markedly high fibronectin-binding capacity, suggesting a possible relationship between the fibronectin-binding capacity and damaged heart tissue infectivity of the Abiotrophia species. A. defectiva strains which were also highly infective had moderate levels of binding to fibronectin and other extracellular matrix proteins. Most of A. para-adiacens and A. elegans strains showed low or negligible binding capacities to any extracellular matrix proteins tested.