Identification of Streptococcus gallolyticus in tumor samples of Iranian patients diagnosed with colorectal cancer.

Objective: Clinical outcomes of infection by S. gallolyticus have not been investigated extensively. We aimed to determine the prevalence of S. gallolyticus in tumor specimens obtained from Iranian patients diagnosed with colorectal cancer. Polymerase chain reaction was used to confirm the presence of S. gallolyticus in patients' tissue samples.

Results: Of 176 patients, 65 were diagnosed with colorectal cancer whereas 111 did not have any colon disease. No correlation was found between age, colonization with S. gallolyticus, gender, or risk factors. Overall, 72 (40%) patients carried S. gallolyticus; only 29% of the patients without colorectal cancer were positive for S. gallolyticus. Diagnosis of colorectal cancer and presence of S. gallolyticus significantly correlated (P = 0.006; odds ratio = 1.46; 95% CI = 1.21-3.87). Among the patients with colorectal cancer, 39 (60%) were positive with S. gallolyticus (P = 0.006) whereas 33 of 111 (29.7%) control subjects were positive for S. gallolyticus (P > 0.05); thus, 70.3% of the control subjects were not infected with S. gallolyticus. We found a high prevalence of S. gallolyticus among an Iranian cohort of patients with colorectal cancer. Despite previous reports, we report a positive correlation between colorectal cancer and S. gallolyticus colonization.