Oral viridans streptococci (comprising *S. mutans*, *S. mitis*, and *S. sanguinis*) represent a category of Gram-positive, catalase-negative, alpha-hemolytic bacteria that are optochin-resistant and bile-insoluble, distinct from *Streptococcus pneumoniae*. The core pathophysiological mechanism involves the species-specific virulence factors: biofilms facilitating oral adhesion for caries/gingivitis in *mutans/mitis*, and dextrans promoting fibrin-platelet aggregation on damaged subendothelium to seed vegetations in *sanguinis*. This theory establishes that bacteremia induced by oropharyngeal manipulation creates a high-risk pathway for infective endocarditis exclusively in hosts with pre-existing valvular damage, necessitating antibiotic prophylaxis.
Oral viridans streptococci (comprising *S. mutans*, *S. mitis*, and *S. sanguinis*) represent a category of Gram-positive, catalase-negative, alpha-hemolytic bacteria that are optochin-resistant and …