The gut virome in Irritable Bowel Syndrome differs from that of controls

Irritable Bowel Syndrome (IBS), the most common gastrointestinal disorder, is diagnosed solely on symptoms. Potentially diagnostic alterations in the bacterial component of the gut microbiome (the bacteriome) are associated with IBS, but despite the known role of the virome (particularly bacteriophages), in shaping the gut bacteriome, few studies have investigated the virome in IBS. We performed metagenomic sequencing of fecal Virus-Like Particles (VLPs) from 55 patients with IBS and 51 control individuals. We detected significantly lower alpha diversity of viral clusters comprising both known and novel viruses (viral 'dark matter') in IBS and a significant difference in beta diversity compared to controls, but not between IBS symptom subtypes. The three most abundant bacteriophage clusters belonged to the Siphoviridae, Myoviridae and Podoviridae families (Order Caudovirales). Limited core viromes (defined as a cluster present in at least 50 % of samples) of five and twelve clusters were identified in IBS and control subjects, respectively. We also identified a subset of viral clusters that showed differential abundance between IBS and controls. The virome did not co-vary significantly with the bacteriome, with IBS clinical subtype or with Bile Acid Malabsorption status. We found no evidence for a shift from lytic to lysogenic replication of core viral clusters, a phenomenon reported for the gut virome of patients with Inflammatory Bowel Disease. Collectively, our data show alterations in the virome of patients with IBS, regardless of clinical subtype, which may facilitate developing new microbiome-based therapeutics.