Streptococcus sanguis, a viridans streptococcus, is most commonly associated with which clinical condition?

• A. Otitis media
• B. Pharyngitis
• C. Relapsing fever
• D. Subacute bacterial endocarditis

Answer: (D)

Streptococcus sanguinis is a member of the viridans group that normally inhabits the oral cavity. The important concept is its tendency to cause endocarditis when it enters the bloodstream and adheres to damaged heart valves. These organisms produce dextran and other surface components that help them stick to fibrin-platelet vegetations on defective valves, leading to a subacute endocarditis with gradually developing symptoms. This association is why it’s classically tied to subacute bacterial endocarditis, particularly in patients with prior valve abnormalities. Otitis media, pharyngitis, and relapsing fever are typically caused by other organisms (such as pneumococcus or H. influenzae for ear infections, group A Streptococcus for throat infections, and Borrelia for relapsing fever), not viridans streptococci.