A chicken-origin Ligilactobacillus agilis R22 exerts probiotic features including growth-promotion and anti-Salmonella infection.

INTRODUCTION

In the quest for the development of antibiotic alternatives, this study aimed to systematically evaluate the probiotic potential and mechanism of action of Ligilactobacillus agilis R22, a novel strain isolated from chickens.

METHODS

The in vitro probiotic properties of L. agilis R22, including growth ability, gastrointestinal tolerance, and antimicrobial activity, were initially assessed. Genomic and untargeted metabolomic analyses were conducted to explore its genetic and metabolic profiles. For in vivo evaluation, dietary supplementation of R22 was performed in broilers to assess growth performance, gut morphology, microbiota, and metabolites. Furthermore, a Salmonella enterica serovar Pullorum infection model in chicks and a fecal microbiota transplantation (FMT) experiment in mice were established to investigate its protective efficacy and underlying mechanisms.

RESULTS

L. agilis R22 exhibited robust growth, high tolerance to simulated gastrointestinal environments, and significant antimicrobial activity. Omics analyses revealed multiple probiotic-associated genes, an absence of virulence genes, and the capacity to synthesize essential nutrients for the host. In broilers, R22 supplementation significantly improved growth performance, intestinal morphology, and increased the levels of ghrelin and insulin-like growth factor-1. While the overall gut microbiota structure was not significantly altered, beneficial species and specific intestinal metabolites were enriched. In the S. Pullorum infection model, R22 effectively inhibited pathogen colonization in the gut and systemic dissemination to other organs, significantly mitigating pathological changes. Additionally, the FMT mouse model provided evidence that the in vivo protective effects of R22 are mediated by the gut microbiota it remodels.

DISCUSSION: The affected intestinal metabolites and the remodeled gut microbiota collectively contribute to the in vivo beneficial effects of L. agilis R22. Taken together, L. agilis R22 is a promising probiotic candidate that can be utilized in microbial feed additives.