Microbial Dynamics in Newly Diagnosed and Treatment Naive IBD Patients in the Mediterranean

Background Microbial communities have long been suspected to influence inflammatory processes in the gastrointestinal tract of patients with inflammatory bowel disease. However, these effects are often influenced by treatments and can rarely be analyzed in treatment-naive onset cases. Specifically, microbial differences between IBD pathologies in new onset cases have rarely been investigated and can provide novel insight into the dynamics of the microbiota in Crohn's disease (CD) and ulcerative colitis (UC). Methods Fifty-six treatment-naive IBD onset patients (67.3% CD, 32.7% UC) and 97 healthy controls were recruited from the Maltese population. Stool samples were collected after diagnosis but before administration of anti-inflammatory treatments. Fecal microbial communities were assessed via 16S rRNA gene sequencing and subjected to ecological analyses to determine disease-specific differences between pathologies and disease subtypes or to predict future treatment options. Results We identified significant differences in community composition, variability, and diversity between healthy and diseased individuals-but only small to no differences between the newly diagnosed, treatment-naive UC and CD cohorts. Network analyses revealed massive turnover of bacterial interactions between healthy and diseased communities, as well as between CD and UC communities, as signs of disease-specific changes of community dynamics. Furthermore, we identified taxa and community characteristics serving as predictors for prospective treatments. Conclusion Untreated and newly diagnosed IBD shows clear differences from healthy microbial communities and an elevated level of disturbance, but only the network perspective revealed differences between pathologies. Furthermore, future IBD treatment is to some extent predictable by microbial community characteristics. Lay Summary Treatment-naive IBD onset patients from Malta show clear differences from healthy microbial communities and an elevated level of community disturbance, although differences between pathologies are only revealed by a network perspective. Furthermore, future IBD treatment is predictable by microbial community characteristics.