# Exosomes in cerebrospinal fluid as biomarkers of bacterial infections of the central nervous system: a pilot study

## TL;DR

This pilot study explores whether exosomes in cerebrospinal fluid can help diagnose bacterial infections in the brain and spinal cord.

## Contribution

The study introduces CSF exosome concentration and size as potential novel biomarkers for central nervous system infections.

## Key findings

- Infected CSF had significantly higher exosome concentrations than non-infected groups.
- Exosomes in infected CSF were significantly larger in diameter compared to other groups.
- Exosomes were detectable in most CSF samples, suggesting their potential for diagnostic use.

## Abstract

Intracranial infections present a significant diagnostic challenge. This pilot study aimed to evaluate the potential of cerebrospinal fluid (CSF)-derived exosomes as novel diagnostic biomarkers for bacterial central nervous system infections.

We enrolled nine patients from Changsha Central Hospital, forming three groups: culture-confirmed intracranial infection (n=3), cerebral hemorrhage with bloody CSF (n=3), and cerebral hemorrhage with clear CSF (n=3). Exosomes were isolated from CSF via ultracentrifugation and characterized using transmission electron microscopy and nanoparticle tracking analysis to assess morphology, concentration, and particle size. Statistical differences between groups were analyzed.

Exosomes were successfully detected in all but one clear-CSF patient. The infected CSF group exhibited a significantly higher mean exosome concentration (1.37e+11 ± 4.40e+10 particles/ml) compared to the bloody (4.08e+9 ± 1.95e+9 particles/ml) and clear CSF groups (1.10e+9 ± 0.56e+9 particles/ml; both p<0.001). Exosome diameter was also significantly larger in infected CSF (167.78 ± 18.65 nm) than in bloody (146.63 ± 6.92 nm) and clear CSF (123.77 ± 13.68 nm; both p<0.001).

This study demonstrates that both the concentration and size of CSF exosomes are significantly elevated in patients with intracranial infections. These findings suggest CSF exosomes hold promise as valuable diagnostic biomarkers, though validation in larger cohorts is necessary to confirm their clinical utility.