# Gut microbiota and traumatic brain injury: insights from an antibiotic-free cohort

## TL;DR

This study shows that traumatic brain injury is linked to changes in gut bacteria, including reduced production of beneficial compounds and increased harmful bacteria.

## Contribution

The study provides novel human evidence of gut microbiota dysbiosis in TBI patients within days of injury, using an antibiotic-free cohort.

## Key findings

- TBI patients showed altered gut microbiota beta diversity and increased variability compared to healthy controls.
- SCFA-producing taxa were depleted, while dysbiosis-associated genera like Escherichia and Shigella were enriched in TBI patients.
- A machine learning model using gut microbiota and clinical variables moderately predicted Glasgow Coma Scale scores.

## Abstract

Traumatic brain injury (TBI) is a major global health concern, leading to persistent neurological deficits and systemic complications. While animal studies have shown the association between TBI and the gut microbiota, human evidence, particularly in the early post-injury period, remains scarce.

In this study, we profiled the gut microbiota of TBI patients within 8 days of hospitalization using 16S rRNA sequencing, integrating clinical metadata and excluding individuals who had received antibiotics within the preceding month.

Although alpha diversity remained similar between groups, beta diversity was significantly altered in TBI patients relative to healthy controls, accompanied by increased inter-individual variability. Differential abundance analysis revealed a depletion of short-chain fatty acid (SCFA)-producing taxa, e.g., Eubacterium, Agathobacter, and Faecalibacillus intestinalis, alongside an enrichment of dysbiosis-associated genera, including Escherichia and Shigella. Notably, Lactobacillus, a γ-aminobutyric acid-producing genus, was elevated in TBI patients, potentially reflecting a compensatory response to neural injury. Functional prediction suggested reduced SCFA biosynthetic capacity in TBI patients, whereas biofilm formation and several other fitness-related processes were enriched. Integrating gut microbiota with clinical and demographic variables, a machine learning model moderately predicted Glasgow Coma Scale scores, with age, inflammatory markers, and differentially abundant bacterial taxa as major contributors.

Collectively, these findings indicate that TBI is associated with dysbiosis of the gut microbial and altered metabolic potential.