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Background and Aim. Because genetic and geographic variations in intestinal microbiota are known to exist, the focus of this study was to establish an estimation of microbiota in colorectal cancer (CRC) patients in Saudi Arabia by means of metagenomic studies. Methods. From July 2010 to November 2012, colorectal cancer patients attending our hospital were enrolled for the metagenomic studies. All underwent clinical, endoscopic, and histological assessment. Mucosal microbiota samples were collected from each patient by jet-flushing colonic mucosa with distilled water at unified segments of the colon, followed by aspiration, during colonoscopy. Total purified dsDNA was extracted and quantified prior to metagenomic sequencing using an Illumina platform. Satisfactory DNA samples (n=29) were subjected to metagenomics studies, followed by comprehensive comparative phylogenetic analysis. An equal number of healthy age-matched controls were also examined for colonic mucosal microbiota. Results. Metagenomics data on 29 patients (14 females) in the age range 38–77 years were analyzed. The majority 11 (37%) of our patients were overweight (BMI = 25–30). Rectal bleeding was the presenting symptom in 18/29 (62%), while symptomatic anemia was the presenting symptom in 11/29 (37%). The location of colon cancer was rectal in 14 (48%), while cecal growth was observed in 8 (27%). Hepatic flexure growth was found in 1 (3%), descending colonic growth was found in 2 (6%), and 4 (13%) patients had transverse colon growth. The metagenomics analysis was carried out, and a total of 3.58G reads were sequenced, and about 321.91G data were used in the analysis. This study identified 11 genera specific to colorectal cancer patients when compared to genera in the control group. Bacteroides fragilis and Fusobacterium were found to be significantly prevalent in the carcinoma group when compared to the control group. Conclusion. The current study has given an insight into the microbiota of colorectal cancer patients in Saudi Arabia and has identified various genera significantly present in these patients when compared to those of the control group.

Abstract Background The focus of this study was to explore potential differences in colonic mucosal microbiota in irritable bowel syndrome (IBS) patients compared to a control group utilizing a metagenomic study. Methods Mucosal microbiota samples were collected from each IBS patient utilizing jet‐flushing colonic mucosa in unified segments of the colon with distilled water, followed by aspiration, during colonoscopy. All the purified dsDNA was extracted and quantified before metagenomic sequencing using an Illumina platform. An equal number of healthy age‐matched controls were also examined for colonic mucosal microbiota, which were obtained during screening colonoscopies. Results The microbiota data on 50 IBS patients (31 females), with a mean age 43.94 ± 14.50 (range19–65), were analyzed in comparison to 50 controls. Satisfactory DNA samples were subjected to metagenomics study, followed by comprehensive comparative phylogenetic analysis. Metagenomics analysis was carried out, and 3.58G reads were sequenced. Community richness (Chao) and microbial structure in IBS patients were shown to be significantly different from those in the control group. Enrichment of Oxalobacter formigenes, Sutterella wadsworthensis, and Bacteroides pectinophilus was significantly observed in controls, whereas enrichment of Collinsella aerofaciens, Gemella morbillorum, and Veillonella parvula Actinobacteria was observed significantly in the IBS cohort. Conclusion The current study has demonstrated significant differences in the microbiota of IBS patients compared to controls.