Intestinal dysbiosis in critically ill patients: a case-control study of Enterobacteriaceae enrichment and reduced...

Critical illness disrupts gut microbiota homeostasis, potentially exacerbating systemic inflammation and adverse outcomes. This study investigates gut dysbiosis patterns in ICU patients, with a focus on Enterobacteriaceae enrichment and microbial diversity loss, to identify biomarkers and therapeutic targets.

In this case-control study, 37 ICU patients (sepsis: n = 17; non-sepsis: n = 20) and 20 healthy controls were enrolled. Fecal samples underwent 16S rRNA sequencing (V3-V4 regions). Microbial diversity (Shannon/Simpson indices), beta diversity (Bray-Curtis PCoA), and taxonomic differences (LEfSe, LDA > 2.5) were analyzed using QIIME2 and R.

Critically ill patients showed reduced alpha diversity vs. controls (Shannon p = 0.04; Simpson p = 0.04). Enterobacteriaceae (phylum Proteobacteria) were significantly enriched in ICU patients (LDA = 4.2, p < 0.01), while Ruminococcus dominated controls. Beta diversity differed markedly (PERMANOVA R ² = 0.199, p = 0.001). No diversity differences were observed between sepsis/non-sepsis subgroups (p > 0.05).

ICU patients exhibit gut dysbiosis characterized by Enterobacteriaceae expansion and diversity loss, independent of sepsis status. These findings underscore the gut microbiome's role in critical illness and support exploring microbiota-targeted interventions (e.g., selective probiotics) to improve outcomes.