A 30-year-old man develops a high fever and malaise. His roommate takes him to the emergency department of a local hospital. On examination by the physician, he is found to have vital signs with T 39.1 C, P 105, R 16, and BP 80/40 mm Hg. On auscultation of the chest, a loud murmur is heard. A blood culture is drawn. An echocardiogram is performed.

He is given IV antibiotic therapy and appears to be improving over the next 36 hours, but then he has a sudden loss of consciouness and there is right papilledema. Emergent MR imaging with gadolinium enhancement of the brain is performed.

Question 9.1 - What is the most likely diagnosis for his presenting illness?

He had infective endocarditis (acute bacterial endocarditis)

Question 9.2 - What is the blood culture most likely to grow?

S. aureus is most likely. Other possibilities include P. aeruginosa as well as streptococci or enterococcus.

Question 9.3 - What antibiotic regimen is indicated?

For Staphylococci, methicillin (or nafcillin) and, if resistant, vancomycin. If vancomycin resistant, then linezolid

Question 9.4 - What did the echo show?

The echocardiogram likely showed valvular vegetations.

Question 9.5 - Explain the complication involving the brain.

Mycotic aneurysms are usually located distal to the first bifurcation of major arteries of the circle of Willis. Most result from infected emboli due to bacterial endocarditis causing septic degeneration of arteries and subsequent dilatation and rupture. Whether these lesions should be sought and repaired prior to rupture, or left to heal spontaneously, is controversial.