A step closer to understanding how a diet high in simple carbohydrates may cause dysbiosis.

The gut microbiota is an integral part of the human metaorganism that is required to shape physiologic host immune responses including host defense against pathogens. Disease-associated gut dysbiosis has been characterized by blooms of pathobionts, which are bacterial species that can drive disease under certain conditions. Pathobionts like Enterobacteriaceae often bloom during flares of inflammatory bowel disease (IBD) and are causally linked with IBD in murine models. In this issue of the JCI, Hecht and colleagues investigated how simple carbohydrates are causally linked to the bloom of the gut pathobiont Klebsiella pneumoniae, which belong to the Enterobacteriaceae family. Notably, the presence of fiber reduced the dissemination of K. pneumoniae into the blood and liver in a colitis model. Their findings provide a diet-related mechanism for gut dysbiosis, which has implications in the management of IBD and other conditions in which gut dysbiosis is an underlying factor.