Diagnostic Yield of Colonoscopy in the Setting of Viridans Streptococcus Bacteremia

Introduction: While the link between Streptococcus (S.) gallolyticus bacteremia and colorectal adenocarcinomas is well-established, bacteremia due to other viridans streptococci species, such as Streptococcus mitis and Streptococcus anginosus, can also be found in the setting of colorectal cancers and precursor lesions. Colonoscopy is the standard of care in evaluating S. gallolyticus bacteremia and it is occasionally recommended in the setting of viridans streptococci bacteremia. Data underlying these associations and recommendations are based on case reports and epidemiologic studies. We present a single-center retrospective study to evaluate the diagnostic yield of colonoscopy in the setting of viridans streptococci bacteremia. Methods: IRB exemption was obtained from TJUH. The laboratory was queried for all patients who had viridans streptococcus bacteremia between April 2017 and March 2021. The medical records of patients with S. gallolyticus, S. anginosus, and S. mitis bacteremia were evaluated for colonoscopy findings within 1 year of the positive cultures. Exclusion criteria included patients with polymicrobial bacteremia (>3 strains). The proportion of colorectal adenocarcinomas and multiple polyps (defined as >2 polyps) among these groups were analyzed with the Fischer’s exact test. Results: The number of patients found to have S. gallolyticus, S. anginosus, and S. mitis bacteremia are shown (Table 1). Of note, 6 of the 9 patients who underwent colonoscopy within a year of S. gallolyticus bacteremia were found to have either multiple polyps or colorectal cancer. Patients with S. gallolyticus bacteremia were more likely to have colorectal cancer found on colonoscopy compared to those with S. mitis (P=0.015), but were not more likely to have multiple polyps identified (P=0.309). There was no statistical difference in the proportion of colorectal cancer or multiple polyps on colonoscopy when comparing patients with S. gallolyticus and S. anginosus bacteremia. Conclusion: The known association between S. gallolyticus and colorectal cancer is affirmed based on this first-ever retrospective study of its kind. There is a relatively high proportion of colorectal cancer in the setting of S. gallolyticus bacteremia, which substantiates the recommendation for colonoscopy. Comparatively, the diagnostic yield of colonoscopy in the setting of S. anginosus or S. mitis bacteremia is questionable. Further characterization of the patient populations is necessary to elucidate the confounding variables.Table 1.: Table shows the number of patients found to have S. gallolyticus, S. anginosus, and S. mitis bacteremia followed by the number of these patients that underwent colonoscopy within 1 year of the bacteremia and the findings on the colonoscopy (categorized as multiple polyps or colorectal cancer). Multiple polyps are defined as more than 2 polyps on colonoscopy for which pathology shows tubular or villous adenomas.