A patient with large, penetrating vegetations on his mitral and aoic valves develops severe headaches. Funduscopic examination reveals papilledema. CT scan of the brain demonstrates a ring-enhancing lesion. Which of the following organisms is the most likely cause of the patient’s disorder?
**Core Concept**
The patient's symptoms, including severe headaches, papilledema, and a ring-enhancing lesion on CT scan, are suggestive of a cerebral abscess, which is a collection of pus in the brain tissue. This condition is often caused by bacterial infections, particularly those that originate from endocarditis, where bacteria from the heart valves spread to the brain.
**Why the Correct Answer is Right**
The patient's vegetations on the mitral and aortic valves are indicative of infective endocarditis, a condition where bacteria infect the heart valves. The bacteria from the heart valves can embolize to the brain, leading to the formation of a cerebral abscess. The ring-enhancing lesion on the CT scan is characteristic of a cerebral abscess, which is a collection of pus surrounded by a ring of inflammatory cells. The most likely causative organism of this condition is *Staphylococcus aureus*, which is a common cause of endocarditis and subsequent cerebral abscesses.
**Why Each Wrong Option is Incorrect**
* **Option A:** *Streptococcus viridans* is a common cause of subacute endocarditis, but it is less likely to cause cerebral abscesses compared to *Staphylococcus aureus*.
* **Option B:** *Escherichia coli* is a common cause of urinary tract infections and bacteremia, but it is not typically associated with endocarditis or cerebral abscesses.
* **Option D:** *Candida albicans* is a fungus that can cause endocarditis, particularly in immunocompromised patients, but it is less likely to cause cerebral abscesses compared to *Staphylococcus aureus*.
**Clinical Pearl / High-Yield Fact**
Cerebral abscesses are a serious complication of infective endocarditis, and prompt diagnosis and treatment are crucial to prevent neurological sequelae. The presence of a ring-enhancing lesion on CT scan is a characteristic feature of cerebral abscesses, and a high index of suspicion is necessary to diagnose this condition.
**Correct Answer:** C.