# Pyogenic Spondylitis with Epidural Abscess Caused by Streptococcus suis Serotype 2 ST7: Tissue mNGS Confirmation and Whole-Genome Characterization of a Human Isolate

## TL;DR

A farmer developed a rare spinal infection caused by Streptococcus suis, confirmed using advanced genetic and imaging techniques.

## Contribution

This case expands the known clinical manifestations of S. suis and demonstrates the utility of tissue mNGS in diagnosing deep-seated zoonotic infections.

## Key findings

- Tissue mNGS confirmed S. suis in a spinal abscess, supporting its role in pyogenic spondylitis.
- Whole-genome sequencing identified resistance markers and virulence traits in the S. suis isolate.
- The isolate belonged to the Chinese ST7 lineage, linked to prior outbreaks.

## Abstract

Streptococcus suis is an emerging zoonotic pathogen that typically causes bacteremia or meningitis in humans, whereas vertebral osteomyelitis with epidural abscess is exceedingly rare and may be missed. We describe a 65-year-old farmer with fever and severe low back pain after long-term bare-handed handling of raw pig lungs. Pre-treatment blood cultures yielded S. suis identified by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). After transient improvement on empirical therapy, fever recurred with worsening lumbar pain. Contrast-enhanced magnetic resonance imaging (MRI) demonstrated multilevel thoracolumbar pyogenic spondylitis with an epidural abscess and a sub-ligamentous abscess beneath the posterior longitudinal ligament (PLL) extending from L2 to L5. Computed tomography-guided lumbar biopsy followed by tissue metagenomic next-generation sequencing (mNGS) detected S. suis, providing concordant evidence supporting pathogen involvement at the vertebral focus. The bloodstream isolate (SS-JX2025-01) was serotype 2, sequence type 7 (ST7). It remained susceptible to β-lactams and glycopeptides but was resistant to macrolide–lincosamide and tetracycline classes, consistent with erm(B), tet(O), tet(40), and ant(6)-Ia detected by whole-genome sequencing (WGS). Virulence profiling revealed an epf+/sly+/mrp− pattern with multiple adhesins and immune-evasion factors, whereas canonical 89K pathogenicity island markers were absent. Core-genome phylogeny placed SS-JX2025-01 within the Chinese ST7 lineage associated with previous outbreaks. This biopsy-supported case expands the clinical spectrum of invasive S. suis infection, highlights the value of tissue mNGS as an adjunct for supporting deep-seated foci in zoonotic infections, and underscores the importance of occupational prevention in small-scale farming households.