Streptococcus bovis/Streptococcus equinus complex fecal carriage, colorectal carcinoma, and infective endocarditis: a new appraisal of a complex connection

The proportion of group D streptococcal infective endocarditis (IE) (predominantly due to Streptococcus gallolyticus) and the incidence of colorectal cancer are higher in France than in most European countries. We assumed that this could be explained by a high group D streptococci (GDS) fecal carriage rate. The aims of this study were to re-assess the GDS fecal carriage rate in France and its relationship with colorectal cancer. Consecutive adult subjects who were to undergo a complete colonoscopy were invited to participate. GDS were searched in subjects’ stools before their colonoscopy using biomolecular techniques. Colonoscopic findings were sorted into four subgroups: normal colonoscopy, non-tumoral lesions, benign tumors, and premalignant/malignant tumors. GDS fecal carriages were calculated overall and in each subgroup and compared. The data from 259 subjects were analyzed. GDS were identified in the feces of 12 subjects, with the following distribution: S. lutetiensis (n = 9), S. pasteurianus (n = 2), and S. gallolyticus (n = 1). This accounted for an overall GDS fecal carriage rate of 4.6 %. The GDS fecal carriage rate was 6 % in case of normal colonoscopy, 1.3 % in case of non-tumoral lesions, 3.2 % in case of benign tumors, and 11 % in case of premalignant/malignant tumors. These four percentages were not statistically different. The GDS fecal carriage rate was lower than expected, which did not confirm our working hypothesis. Most strains belonged to S. bovis biotype II, while S. gallolyticus was found only once. These findings suggest that different GDS play different roles in the etiopathogenesis of IE and colorectal cancer.