A 55-year-old man presents to the emergency department with recurrent fevers over the past 6 weeks. Blood cultures are performed and eventually show an organism that is purple on Gram stain, does not cause hemolysis when plated, and does not survive in 6.5% NaCl. An echocardiogram reveals the presence of native valve endocarditis.
For which of the following conditions should this patient be evaluated to determine the etiology of the endocarditis?
- A) Dental caries
- B) Intravenous drug use
- C) Malignancy of the lower GI tract
- D) Urinary tract infection
- E) Vegetations on intravenous catheter
C) Malignancy of the lower GI tract
The blood culture findings in this case is consistent with Streptococcus bovis. Infective endocarditis by Streptococcus bovis is often associated with colorectal cancer. This is in contrast to enterococcus which can cause urinary tract infections as well as infective endocarditis. The test to differentiate between these two organisms is growth in 6.5% NaCl. Poor dentition is a risk factor for infective endocarditis due to oral flora. Intravenous drug use can lead to infective endocarditis from skin flora, oral flora, or organisms contaminating the drug or materials used for injection. Urinary tract infection is an uncommon cause of endocarditis. Enterococcus faecalis can cause endocarditis, but bacteremia in the setting of enterococcal urinary tract infection is uncommon. This patient does not have an intravenous catheter, so that is not a risk factor in this case.
Key Learning Point
Streptococcus bovis is purple on Gram stain, does not cause hemolysis when plated, and does not survive in 6.5% NaCl, which differentiates it from Enterococcus which does survive in 6.5% NaCl. Bacteremia or infective endocarditis with Streptococcus bovis is often associated with colorectal cancer.