SERUM AND FECAL PROFILES OF AROMATIC MICROBIAL METABOLITES REFLECT THE GUT MICROBIOTA DISRUPTION IN CRITICALLY ILL PATIENTS

BackgroundHigh serum levels of certain aromatic microbial metabolites (AMM) are associated with severity and mortality of critically ill patients. Omics-based studies suggest gut dysbiosis and reduced microbiome diversity in critical conditions. However, the landscape of the gut microbial metabolites is still to be outlined, not to mention the interplay between the metabolome and gutmicrobiome in critically ill patients. The aim of this work was to analyze the association between serum and fecal levels of AMM and compare them with the composition of the gut microbiota in ICU patients in the acute and chronic stages.MethodsWe analyzed temporal dynamics of gut microbiome and AMM spectrum across the two distinct subgroups of critically ill patients - acute critical illness (ACI) with nosocomial pneumonia and chronically critically ill patients (CCI). The AMM levels for each patient were measured using GC/MS in simultaneously taken serum and fecal samples (SFS). These parameters werecompared with 16S rRNA fecal microbiome profiles.ResultsThe observed proportions of bacterial taxa suggest a significant gut dysbiosis in ACI and CCI. Stronger imbalance in microbiome composition and dynamics observed in ACI patients compared to CCI group resonates with a higher severity in the former group. The summary levels of AMM in serum samples were higher for ACI patients than for the CCI patients (3.7(1.4-6.3) and 1.1 (1.0-1.6) μM, respectively; p=0.0003). The qualitative composition of SFS was also altered. We discovered remarkable associations between gut microbial taxa levels, metabolite concentrations in blood serum and feces in each of the ACI and CCI groups.ConclusionAromatic microbial metabolite profiles in gut and serum are interlinked and reflects the disruption and loss of biodiversity of the gut microbiota in critically ill patients.