Disarming Campylobacter hepaticus – the in vitro and in vivo efficacy of natural antimicrobials as anti-virulence proxies

Campylobacter hepaticus is responsible for the emergence of Spotty Liver Disease (SLD) in commercial layer hens. Our experimental in vitro approach demonstrates that natural antimicrobial mixtures (AuraShield - As) can significantly inhibit (P < 0.0001) the growth and motility of C. hepaticus. The antimicrobial acted as a chemoattractant for the pathogen, an effect which is concentration-dependent and leads to reduced bacterial motility. The As reduced C. hepaticus invasion of chicken liver cells (LMH cells) by strengthening TEER. The As also modulates inflammatory responses (notably by lowering IL-8 expression via the NF-κB pathway) and enhances host cell defences. We demonstrate that the presence of As (0.5%) during the infection of LMH cells by C. hepaticus significantly mitigates oxidative stress by reducing the detectable levels of H₂O₂ released into the culture supernatants (P<0.0001). We also show that a reduced H₂O₂ level will not activate the NF-kB pathway, resulting in low levels of IL-8 orthologs expression. In vivo, As was able to significantly reduce (P=0.03) not only the number of C. hepaticus identified in the livers of the infected hens but also the number of liver lesions, while restoring the integrity of the intestinal barrier. These in vitro and in vivo findings present new opportunities for enhanced SLD management strategies that integrate dietary innovations with improved flock biosecurity. By adopting a holistic approach that combines dietary, environmental, and management interventions, producers may achieve more sustainable and effective outcomes in the ongoing battle against Campylobacter hepaticus and Spotty Liver Disease.