Question:
A lady with congenital heart disease underwent a dental extraction and developed endocarditis. Which is the organism most likely to have been involved in the pathogenesis?
A lady with congenital heart disease underwent a dental extraction and developed endocarditis. Which is the organism most likely to have been involved in the pathogenesis?
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Mouth flora enter the blood during dental work; viridans streptococci are the classic culprit in endocarditis after dental extraction.
Updated On: Jul 8, 2026
- Staphylococcus aureus
- Streptococcus pneumoniae
- Streptococcus sanguis
- Staphylococcus epidermidis
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The Correct Option is C
Solution and Explanation
Step 1: Read the clinical picture.
The woman already has congenital heart disease, so her heart valves are not normal. A dental extraction was done, and soon after she developed endocarditis (infection of the heart valve lining).
Step 2: Link dental work to bacteremia.
Dental extraction damages the gums and lets mouth bacteria enter the blood for a short time. This is called transient bacteremia. In a normal heart this bacteremia clears on its own, but in a heart with an existing defect the abnormal valve surface lets bacteria stick and grow.
Step 3: Identify the usual organism from the mouth.
The main bacteria living in the mouth and gums are the viridans group streptococci, which includes Streptococcus sanguis, Streptococcus mitis and Streptococcus mutans. These organisms are low virulence but stick well to damaged or abnormal valve tissue, which is exactly why they are the classic cause of subacute bacterial endocarditis after a dental procedure.
Step 4: Rule out the other organisms.
Staphylococcus aureus causes a fast, aggressive (acute) endocarditis, most often seen in intravenous drug users or after skin infections, not after dental work.
Streptococcus pneumoniae is a respiratory organism that causes pneumonia and meningitis, and is a rare cause of endocarditis.
Staphylococcus epidermidis lives on skin and is mainly linked to infection of prosthetic (artificial) heart valves and catheters, not native valve endocarditis after a dental extraction.
Final Answer:
The organism most likely involved is the viridans streptococcus from the mouth.
\[ \boxed{\text{Streptococcus sanguis}} \]
The woman already has congenital heart disease, so her heart valves are not normal. A dental extraction was done, and soon after she developed endocarditis (infection of the heart valve lining).
Step 2: Link dental work to bacteremia.
Dental extraction damages the gums and lets mouth bacteria enter the blood for a short time. This is called transient bacteremia. In a normal heart this bacteremia clears on its own, but in a heart with an existing defect the abnormal valve surface lets bacteria stick and grow.
Step 3: Identify the usual organism from the mouth.
The main bacteria living in the mouth and gums are the viridans group streptococci, which includes Streptococcus sanguis, Streptococcus mitis and Streptococcus mutans. These organisms are low virulence but stick well to damaged or abnormal valve tissue, which is exactly why they are the classic cause of subacute bacterial endocarditis after a dental procedure.
Step 4: Rule out the other organisms.
Staphylococcus aureus causes a fast, aggressive (acute) endocarditis, most often seen in intravenous drug users or after skin infections, not after dental work.
Streptococcus pneumoniae is a respiratory organism that causes pneumonia and meningitis, and is a rare cause of endocarditis.
Staphylococcus epidermidis lives on skin and is mainly linked to infection of prosthetic (artificial) heart valves and catheters, not native valve endocarditis after a dental extraction.
Final Answer:
The organism most likely involved is the viridans streptococcus from the mouth.
\[ \boxed{\text{Streptococcus sanguis}} \]
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