The single degree of polymerization influences the efficacy of xylooligosaccharides in shaping microbial and metabolite profiles in chicken gut to combat avian pathogenic Escherichia coli.

BACKGROUND

Avian pathogenic Escherichia coli (APEC) threatens both poultry production and human health. Xylooligosaccharides (XOS) may suppress pathogenic bacteria through prebiotic actions. However, the influences of single degree of polymerization (DP) on the inhibition of APEC by XOS remain unknown. This study aimed to probe if XOS and their major monomers (xylobiose, xylotriose and xylotetraose) could differentially combat APEC via prebiotic actions using an in vitro fermentation model with chicken cecal microbiota.

METHODS

Microbiota were randomly divided into 7 groups (5 replicate tubes/group). Control group (CON) received no treatment; XOS group received commercial XOS mixtures; APEC group received APEC; XA, X2, X3 and X4 groups received APEC combined with commercial XOS mixtures, xylobiose, xylotriose and xylotetraose, respectively.

RESULTS

XOS and their major monomers mitigated APEC-induced decline (p < 0.05) in gut microbial α-diversity, with xylotetrose showing the least effect. Gut microbiota in XA, X2, X3 and X4 groups clustered together, with a relative separation observed in X4 group. XOS and their monomers elevated (p < 0.05) the abundances of Firmicutes, Bacteroidota and several probiotics (Lactobacillus, Bacteroides and Megamonas), but reduced (p < 0.05) the abundances of Proteobacteria and Escherichia-Shigella, with xylotetraose exhibiting the least efficacy. Besides, xylotriose and xylotetrose had an advantage over xylotetraose in promoting microbial production of short-chain fatty acids. Metabolomics analysis revealed that APEC challenge mainly downregulated (p < 0.05) several amino acids metabolism pathways of gut microbiota, while xylotriose had an inferiority to XOS in upregulating (p < 0.05) histidine metabolism pathway. Furthermore, microbial fermentation metabolites of all XOS monomers lowered (p < 0.05) certain virulence genes expression in APEC, with xylotriose being the most advantageous.

CONCLUSIONS

XOS and their major monomers differentially improved gut microbiota and metabolite profiles in chicken gut against APEC challenge. Overall, xylotriose exhibited the greatest inhibition against APEC abundance and virulence. Our findings underscore the role of single DP in influencing the prebiotic actions of XOS against APEC, providing a basis for the reasonable application of XOS in diets to combat bacterial challenge.