Gut Microbiota May Have a Causal Effect on Risk for IBS

Bacterial taxa Actinobacteria, Flavonifractor, and Eisenbergiella may be associated with risk for irritable bowel syndrome (IBS), according to a genome-wide association study (GWAS) published in BMC Gastroenterology.

Approximately 11% of the population will be affected by IBS. Numbers are expected to rise, consequently impairing quality of life for much of the world. While recent research has demonstrated that the gut microbiota may play a role in IBS pathogenesis, this causal relationship is not clear. Researchers aimed to examine the association between gut microbiota and IBS and identify specific bacterial taxa that may be responsible.   

Data for gut microbiota instrumental variables were taken from a GWAS that included 18,340 patients, while data on IBS statistics were retrieved from a GWAS that included 53,400 cases of IBS and 433,201 control patients of European decent. A total of 196 bacterial traits were analyzed for relationships. The main method used was the inverse-variance weighted (IVW) method, with reverse Mendelian randomization (MR) implemented to assess potential reverse causation.

Of the 196 bacteria traits analyzed, IVW results revealed 11 traits may be associated with risk for IBS. More specifically, phylum Actinobacteria(odds ratio [OR], 1.08; P =.011), genus Flavonifractor (OR, 1.10; P =.005) were positively associated with risk for IBS, while genus Eisenbergiella (OR, 0.95; P =.030) was negatively associated.

While the 8 remaining traits were suggestively associated with risk for IBS, a causal relationship could not be confirmed.

Reverse MR analyses did not reveal reverse associations between IBS and phylum Actinobacteria(OR, 1.04; P =.692), genus Flavonifractor (OR, 1.00; P =.980), and genus Eisenbergiella (OR, 0.80; P =.290).

Absence of bacterial taxa analyses at the species or strain levels may have limited the scope of this study. Additionally, generalization is limited due to lack of ethnic diversity in the study population. Finally, data on IBS subtypes were not available.

“Causal association research will be the future direction of studying the role of gut microbiota in the development of diseases. Our MR analysis results may provide a guide for selecting individual gut bacteria to study the role of gut microbiota in the pathogenesis of IBS,” the researchers concluded.

This article originally appeared on Gastroenterology Advisor