Differences in IBS patients' microbiota more significant in feces vs. mucosa
Microbial composition and diversity in unprepared sigmoid colon mucosa differed insignificantly between patients with irritable bowel syndrome and healthy controls compared to the differences in the fecal microbiota between both groups, according to recent study data.
“The main objective of this study was to compare the fecal- and mucosal-associated microbiota in healthy individuals and IBS patients, respectively, as models of physiologically normal and immunologically disturbed intestinal systems,” the researchers wrote. “In addition, our aim was to determine to which extent alterations in the fecal-associated microbiota in IBS, compared to healthy controls, would mirror variations in the mucosal-associated microbiota.”
Mucosal biopsies from the unprepared sigmoid colon were collected from 35 IBS patients and 10 healthy controls, and fecal samples were collected the day before colonoscopy from 33 IBS patients and 16 healthy controls, resulting in 33 and eight paired samples for IBS patients and healthy controls, respectively.
Microbiota composition was analyzed using a phylogenetic microarray and redundancy discriminant analysis was used to determine differences in microbiota profile signatures.
The investigators found clear differences in microbial composition between mucosal and fecal samples of both IBS patients and healthy controls (P = .002), and while these differences were more distinct among IBS patients, there was no association found between microbiota differences and IBS clinical characteristics.
In healthy controls, there was a higher relative abundance of Bacteroidetes in mucosal samples, and a higher relative abundance of Firmicutes (Clostridium cluster XIVa) in the fecal samples (P < .05).
“Remarkably, the number of significantly different microbial groups separating the fecal- and mucosal-associated microbiota in IBS consisted of 107 genus-like bacterial groups,” the researchers wrote. There was higher relative abundance of Bacteroidetes in the mucosa, and higher relative abundance of Actinobacteria, Bacilli, Clostridium clusters IV, IX and XIVa, and Proteobacteria in the feces of IBS patients (cut-off false discovery rate < .05).
The mucosal microbiota was more similar between IBS patients and healthy controls compared to the fecal microbiota of both groups, with the exception of Clostridiales I, which had sixfold higher relative abundance in the mucosa of healthy controls compared to IBS patients (1.9% vs. 0.3%; P < .005).
In IBS patients, bacterial diversity was significantly higher in fecal microbiota compared with mucosal microbiota (P < .005).
The researchers concluded that differences in the mucosal microbiota between IBS patients and healthy controls are minimal (one bacterial group) compared to differences in their fecal microbiota (53 bacterial groups), and that the microbial differences in IBS patients are more prominent in the feces compared to the mucosa. They also attributed the main differences in fecal microbiota between IBS patients and healthy controls to the diarrhea-predominant IBS subgroup, representing nearly half of the IBS cohort. – by Adam Leitenberger
Disclosures: The researchers report no relevant financial disclosures.