Clinical‑microbiotic correlations in ulcerative colitis: bacterial and fungal taxa in disease relapse and remission

Objective: to study the features of the structure of the bacterial and fungal communities in the colon in patients with ulcerative colitis (UC) during the relapse and remission phases, and to identify taxonomic groups that have reliable associations with the clinical and endoscopic activity of the disease. Materials and methods: the study included 86 patients with UC in the relapse phase – the initial clinical cohort, and a subgroup of 42 patients from the initial cohort who achieved disease remission. The taxonomic profile of the colonic microbiota was determined during the relapse and remission phases of UC using 16S and 18S rRNA gene sequencing of stool samples, and the relationships between the composition of the bacterial and fungal microbiota and clinical, laboratory, and endoscopic indicators of UC activity were assessed. Results: intergroup taxonomic analysis revealed differences in the structure of the bacterial microbiota of the colon depending on the phase of UC. The relapse phase was characterized by the predominance of a number of conditionally pathogenic and opportunistic bacteria, whereas in the remission phase, an increase in the proportion of SCFA producers and symbiotic microorganisms was more frequently detected. Predominantly direct correlations with the studied indicators were established for conditionally pathogenic and opportunistic samples, such as Actinomyces spp., Corynebacterium spp., Enterococcus spp., Enterobacter spp., Bradyrhizobium and Escherichia/Shigella, whereas inverse correlations were found for SCFA‑producing and “anti‑inflammatory” microorganisms, such as Alistipes spp., Bifidobacterium spp., Lachnospiraceae NK4A136 group and Ruminococcus bicirculans. The fungal taxa Saccharomyces, Malassezia and Cryptococcus vishniacii demonstrated inverse associations with certain indicators. Conclusions: the correlation analysis revealed statistically significant associations between the relative abundance of individual bacterial and fungal taxa and clinical and endoscopic indicators. According to the obtained results individual components of the microbiota can be considered as potential markers of disease activity.

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