Monday, October 29, 2007

How Now Brown Cow

A 55-year-old immigrant from France without known history of IV drug use or structural heart disease presents with the signs and symptoms of infective endocarditis. You isolate an unusual organism, a Gram positive coccus susceptible to penicillin that is non-hemolytic on blood agar. It grows in 40% bile but not 6.5% NaCl and hydrolyzes esculin but not arginine.

Your attending tells you to do a colonoscopy.

Challenge: What is the organism? Why the colonoscopy?


Alex said...

hmm, weird. i read up on gram+ but forgot a lot of the details. You gave a lot of lab hints, but I won't cheat by looking this up.

Anyway, I think it is one of the Streps. Maybe Group A. The colon thing throws me off though, it makes me think C dificile.

Craig said...

How Now Brown Cow

The organism (as you might suspect from the case title) is Streptococcus bovis, which has the properties listed in the case as well as being PYR negative. Streptococcus bovis is associated with colonic neoplasia and colon cancer, thus indicating the colonoscopy. Mechanism is unknown.

The epidemiology shows that Strep bovis infective endocarditis varies by country and age; France has the highest proportion of Strep bovis isolated from streptococcus infective endocarditis. Also, 80% of patients with this organism are older than 50.

Source: UpToDate

Stephanie said...

OMG, Craig, you are too crazy! In a good come you never study the syllabus this hard??