Background and Aim: The human bowel contains a large and dynamic bacterial population (more than 500 species of bacteria). Some intestinal bacteria such as Streptococcus bovis , Enterococcus and Bacteroides fragilis have previously been suggested to be implicated in the promotion of colon carcinogenesis probably through the conversion of mutagen metabolites.

Materials and Methods: Thirty patients with colorectal cancer confirmed by colonoscopy examination and pathological survey were evaluated. Thirty healthy people who matched by sex and age with patient group were identified. Fecal samples were collected from patient and control groups were cultured in specific and non-specific culture media (aerobic and nonaerobic situations).Organisms isolated by microbial and biochemical pathways.

Results: S. bovis was predominant fecal microbial flora in nine (39.1%) patients and six (26.1%) of control group (P=0.657). Entrococcus was predominant fecal microbial flora in 6 (26.1%) patients and 2 (8.7%) of control group (P=0.657). B. fragillis was predominant fecal microbial flora in 8 (21.7%) patients and 2 (5.4%) of control group (P= 0.062).

Conclusion: Our results by fisher statistical analysis show that the incidences of fecal S. bovis, Enterococcus and B. fragilis in colorectal cancer were not significantly higher than health people.