Fecal Microbiota in Patients with Irritable Bowel Syndrome Compared with Healthy Controls Using Real-Time Polymerase Chain Reaction: An Evidence of Dysbiosis

Dysbiosis may play a role in irritable bowel syndrome (IBS), hitherto an enigmatic disorder. We evaluated selected fecal microbes in IBS patients and healthy controls (HC). Fecal 16S rRNA copy number of selected bacteria was studied using qPCR in 47 patients with IBS (Rome III) and 30 HC. Of 47 patients, 20 had constipation (IBS-C), 20 diarrhea (IBS-D), and seven unclassified IBS (IBS-U). Relative difference in 16S rRNA copy number of Bifidobacterium (P = 0.042) was lower, while those of Ruminococcus productus-Clostridium coccoides (P = 0.016), Veillonella (P = 0.008), Bacteroides thetaiotamicron (P < 0.001), Pseudomonas aeruginosa (P < 0.001), and Gram-negative bacteria (GNB, P = 0.001) were higher among IBS patients than HC. Number of Lactobacillus (P = 0.002) was lower, while that of Bacteroides thetaiotamicron (P < 0.001) and segmented filamentous bacteria (SFB, P < 0.001) was higher among IBS-D than IBS-C. Numbers of Bacteroides thetaiotamicron (P < 0.001), P. aeruginosa (P < 0.001), and GNB (P < 0.01) were higher among IBS-C and IBS-D than HC. Quantity of SFB was higher among IBS-D (P = 0.011) and lower among IBS-C (P = 0.002) than HC. Number of Veillonella species was higher among IBS-C than HC (P = 0.002). P. aeruginosa was frequently detected among IBS than HC (46/47 [97.9 %] vs. 10/30 [33.3 %], P < 0.001). Abdominal distension (n = 34/47) was associated with higher number of Bacteroides thetaiotamicron, Clostridium coccoides, P. aeruginosa, SFB, and GNB; bloating (n = 22/47) was associated with Clostridium coccoides and GNB. Microbial flora was different among IBS than HC on principal component analysis. Fecal microbiota was different among IBS than HC, and different sub-types were associated with different microbiota. P. aeruginosa was more frequent and higher in number among IBS patients.