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

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

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

Answer: (B)

Streptococcus sanguis is part of the viridans group that normally inhabits the mouth. The key concept is that these bacteria have a strong ability to adhere to damaged heart valves and to form biofilms by producing extracellular polysaccharides like dextran. When bacteremia occurs—often after dental procedures or even routine dental brushing in people with preexisting valve abnormalities—the organisms can latch onto the valve surface, become embedded in a fibrin-platelet clot, and grow slowly, causing subacute bacterial endocarditis. This pattern of infection fits the typical clinical course of endocarditis caused by viridans streptococci: insidious onset, gradual valvular destruction, and vegetations rather than an abrupt, fulminant illness. Otitis media, pharyngitis, and relapsing fever are associated with other pathogens or disease mechanisms (for example, many cases of otitis media involve Streptococcus pneumoniae or other bacteria, pharyngitis often involves group A Streptococcus or viruses, and relapsing fever is caused by Borrelia species). Thus, the strongest and most characteristic association for S. sanguis is subacute endocarditis.

Streptococcus sanguis is part of the viridans group that normally inhabits the mouth. The key concept is that these bacteria have a strong ability to adhere to damaged heart valves and to form biofilms by producing extracellular polysaccharides like dextran. When bacteremia occurs—often after dental procedures or even routine dental brushing in people with preexisting valve abnormalities—the organisms can latch onto the valve surface, become embedded in a fibrin-platelet clot, and grow slowly, causing subacute bacterial endocarditis. This pattern of infection fits the typical clinical course of endocarditis caused by viridans streptococci: insidious onset, gradual valvular destruction, and vegetations rather than an abrupt, fulminant illness.

Otitis media, pharyngitis, and relapsing fever are associated with other pathogens or disease mechanisms (for example, many cases of otitis media involve Streptococcus pneumoniae or other bacteria, pharyngitis often involves group A Streptococcus or viruses, and relapsing fever is caused by Borrelia species). Thus, the strongest and most characteristic association for S. sanguis is subacute endocarditis.