Mahtab Mehboodi - Department of Medical Microbiology (Bacteriology & Virology), Afzalipour Faculty of Medicine,Kerman University of Medical Sciences, Kerman, Iran
Roya hmadrajabi
Fereshteh Saffari - Gastroenterology and Hepatology Research Center, Kerman University of Medical Sciences, Kerman, Iran
Bijan Ahmadi
Mohammad Javad Zahedi

BACKGROUND AND ABJECTIVEThe intestinal microbiota, composed of a large population of microorganisms, is often considered as “forgotten organ”. Increasing evidences indicate that dysbiosis of the intestinal microbiota is closely related to inflammatory bowel disease (IBD) and colorectal cancer (CRC). Enterotoxigenic Bacteroides fragilis (ETBF) may play a role in the occurrence and progression of colorectal precancerous and cancerous lesions via modulating the mucosal immune responses and inducing changes in structure and physiology of epithelial cells. Also, Although Peptostreptococcus stomatis (P. stomatis) forms part of the commensal microbiome of the human mouth and gut, it is associated with colorectal cancer through an unknown role. This study aimed to determine the frequency of ETBF and P. stomatis in fecal samples of patient with IBD or CRC and healthy individuals.MATERIALS AND METHODSIn this cross-sectional study, from August ۲۰۲۲ to July ۲۰۲۳, fecal samples were collected from healthy controls (N = ۷۴), and patients with IBD (N = ۴۶) and CRC (N = ۲۸) at the time of colonoscopy admitted to Kerman University affiliated hospitals. All of the patients didn’t start chemotherapy or radiation therapy for treatment. Assessment of ۱۶SrRNA and metaloprotease enterotoxin (bft) genes by PCR technique was used for detection of P. stomatis and ETBF isolates, respectively.RESULTS AND DISCUSSIONThe frequency of ETBF among IBD, CRC and control cases was ۲۸.۳%, ۱۴.۳% and ۱۷.۶%, respectively (P > ۰.۰۵). P. stomatis was found among ۵۶.۵%, ۶۰.۷% and ۳۱.۱% of IBD, CRC and control cases, respectively. Colonization by both ETBF and P. stomatis occurred in ۶.۷% of the healthy controls, ۲۱.۷% of the IBD and ۱۴.۳% of the CRC patients. There was a statistically significant difference in the presence of P. stomatis in IBD and CRC cases vs. control ones (P = ۰.۰۰۴).CONCLUSIONThe results show the association between the presence of fecal P. stomatis and intestinal disorders and its elevated levels may be a risk factor for developing CRC. So, detection of P. stomatis may provide a potential marker for CRC diagnosis. However, additional investigations on tumor and paired normal tissue samples are required to substantiate this finding.

Peptostreptococcus stomatis, Enterotoxigenic Bacteroides fragilis, inflammatory bowel disease, colorectal cancer, stool