Colonic carriage of Streptococcus bovis and colorectal neoplasia: a prospective 17-year longitudinal case-control study.

Patients with Streptococcus bovis infective endocarditis have an increased prevalence of advanced colonic neoplasia; however, an association with fecal carriage of the organism is unclear. S. bovis has been shown to promote colonic neoplasia in preclinical studies. The aim of this study was to examine the effect of S. bovis fecal carriage on the long-term risk of colonic neoplasia.Patients were prospectively recruited before colonoscopy. S. bovis was detected by culture in stool, colonic fluid aspirates, and biopsies. Patients continued colonoscopic surveillance at intervals according to accepted guidelines. The National Cancer Registry was checked for diagnoses of colorectal cancer on 31 December 2014.A total of 118 patients were recruited [75 (72.8%) men, aged 64.5±9.3 years] including 15 with S. bovis. The mean duration of follow-up was 190.7±123.5 months. Colonic neoplasia was detected at colonoscopy in six (40.0%) and 49 (47%) patients with and without S. bovis, respectively (P=0.78). At the end of follow-up, colorectal cancer had developed in one (6.7%) S. bovis-positive and six (5.8%) S. bovis-negative patients (P=1.00).Fecal carriage of S. bovis at baseline is not associated with an increased long-term risk of developing colonic neoplasia in this longitudinal study.