Q: 54 year old male is admitted to ICU with infective endocarditis. Blood cultures are growing Clostridium septicum, What is your next concern? 

Answer: Colon cancer 

Clostridium septicum is part of the natural flora of the bowel, and is associated with colonic malignancies. When they present as the causative agent in endocarditis, it is secondary to colon cancer proved otherwise and calls for a concomitant colonoscopy. Another bacteria causing endocarditis and found to be associated with colon malignancy is S. bovis.

Reference:

Chew SSB, Lubowski DZ (2001). "Clostridium septicum and malignancy". ANZ Journal of Surgery 71 (11): 647–649.