الفهرس 
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Abstract
Colorectal cancer (CRC) is the second most common cause of cancer mortality among men and women worldwide; the risk of its occurrence has been shown to be increased by chronic bacterial infections by two mechanisms:inflammation and/or formation of carcinogenic metabolites. Therefore, it might be possible to prevent or treat cancer when the infectious source can be identified.Since the 1980s, there has been a dramatic increase in research on infection and cancer. In 2002, it was reported that infectious agents accounted for about 18% of all cancers worldwide.
One of the bacterial agents associated with cancer colon is Streptococcus bovis (S. bovis). S. bovis has been shown to have important impact on health since 25 to 80% of patients with S. bovis bacteremia have colorectal tumors and the incidence of association of colonic neoplasia with S. bovis endocarditis has been shown to be 18 to 62%.About 65% of population with age more than 60 years are at high risk for colorectal cancer which indicates the need for a proper screening test for the early detection of colorectal cancer. Serological studies found significant association between Streptococcus bovis IgG and colorectal cancer. Therefore, a simple ELISA test might be efficient for screening high risk individuals for the presence of premalignant neoplastic polyps, adenomas and cancers.The present work aimed at studying the correlation between Streptococcus bovis fecal carriage and colorectal cancer. 50 stool samples were collected from colorectal cancer patients as well as 25 samples from apparently healthy individuals. Streptococcus bovis was isolated from 8 stool samples of the patients (16%). All strains were proved to be Streptococcus bovis biotype II/2 by using API 20 STREP Identification System. No similar isolates were present in stool of control group. Also, we found that 87.5% of patients with positive stool culture for Streptococcus bovis were at stage 4 colorectal cancer, and 12.5% were at stage 3. Streptococcus bovis was not isolated from patients of stage 2 colorectal cancer.So, we found a statistically significant association between Streptococcus bovis fecal carriage and colorectal cancer (p = 0.034).
Recommendations:
from the previous study, we recommend the following:
1) Further studies about the association between Streptococcus bovis fecal carriage and colorectal cancer should be carried out on a larger scale.
2) Studying the association between Streptococcus bovis antibodies and colorectal cancer.
3) Studying the association between Streptococcus bovis bacteremia and colorectal cancer.