# Virulence and Immune Response of Campylobacter jejuni Strains in Chicken Embryo Model

## TL;DR

This study examines how different Campylobacter jejuni strains affect chicken embryos, revealing insights into virulence and immune responses.

## Contribution

The study introduces a chicken embryo model to evaluate virulence and immune responses to various Campylobacter jejuni strains.

## Key findings

- CJ strains caused embryo mortality at 3.7 log CFU/CE but not at lower doses.
- Lower doses induced macroscopic and microscopic lesions without killing embryos.
- Immune stimulation varied among CJ strains, indicating strain-specific immune responses.

## Abstract

This study aimed to evaluate the virulence and infection response of Campylobacter jejuni (CJ) strains isolated from chickens, as well as a standard strain isolated from humans, to understand better the pathogen-host relationship between CJ and chicken embryos (CE) with an active immune system. With its well-developed vascular structures, the CE model offers a valuable method for studying complex biological systems. We assessed embryo mortality, weight, macroscopic and microscopic lesions, bacterial multiplication within the embryo, and macrophage and lymphocyte (T and B cell) counts using flow cytometry. Additionally, histopathological lesions were examined. CJ killed CE at a dose of 3.7 log CFU/CE; however, lower doses (2.5 log CFU/CE) did not result in embryo death but instead caused macroscopic damage along with mild to moderate lesions. Certain strains were also capable of stimulating the immune system; however, this response varied depending on the strain. These findings underscore the importance of studying the virulence, infection dynamics, and immune responses of various CJ strains, highlighting the utility of the CE model for these investigations.

The online version contains supplementary material available at 10.1007/s00284-026-04768-7.