Which organism is associated with colon cancer and is a Group D streptococcus?

• A. Staphylococcus aureus
• B. Streptococcus pyogenes
• C. Streptococcus bovis
• D. Streptococcus agalactiae

Answer: (C)

Streptococcus bovis, a Group D streptococcus (often referred to today as Streptococcus gallolyticus), has a well-established association with colorectal neoplasia. It resides in the gut, but when it appears in blood cultures or causes endocarditis, it prompts clinicians to investigate the colon for cancer or polyps with a colonoscopy. This link is what makes this organism the best answer for a question connecting a Group D streptococcus to colon cancer. Other choices represent different organisms with different clinical associations—Staphylococcus aureus is a common skin and bloodstream pathogen, Streptococcus pyogenes is Group A and linked to pharyngitis and rheumatic fever, and Streptococcus agalactiae is Group B and a neonatal pathogen—so they don’t carry the colon cancer connection.