A Rare Case of Streptococcus pasteurianus Endocarditis Signaling Colon Cancer

Infective endocarditis (IE) is a life-threatening condition often associated with various complications. A unique subset of IE cases involves the Streptococcus gallolyticus group, which has a well-documented but sometimes poorly understood association with colonic neoplasms. Specifically, colon cancer has a well-established association with IE caused by S. gallolyticus subspecies (spp.) gallolyticus. However, finding colon cancer in cases of IE due to S. gallolyticus spp. pasteurianus is rather unexpected. Herein, we present a rare instance of IE caused by S. gallolyticus spp. pasteurianus in a 62-year-old male, which led to the discovery of an underlying colorectal carcinoma. Considering the overall elevated risk of colon cancer in patients with endocarditis and in patients with S. bovis/S. equinus complex (SBSEC) bacteremia, we decided to proceed to colonoscopy, which revealed adenocarcinoma. The patient was administered a targeted antibiotic regimen and underwent a successful surgical resection, followed by valve replacement surgery. The outcome of this case supports the recommendation of routine colonoscopic evaluation in patients diagnosed with S. gallolyticus bacteremia, including those with subspecies pasteurianus, particularly when there are other associated findings. It strengthens the argument for conducting a colonoscopy in individuals diagnosed with SBSEC endocarditis, while carefully considering the specifics of each clinical situation. Our report highlights the need for heightened clinical vigilance and an integrated approach to treatment in similar cases.