Effect of oral administration of Microcin Y on growth performance, intestinal barrier function and gut microbiota of chicks challenged with Salmonella Pullorum

Abstract The lasso peptide microcin Y (MccY) effectively inhibits various serotypes of Salmonella in vitro, but the antibacterial effect against S. Pullorum in poultry is still unclear. This study was the first to evaluate the therapeutic activity of MccY in specific pathogen-free (SPF) chicks infected with S. Pullorum. The chicks were randomized into four groups: (I) negative control group (NC), (II) S. Pullorum-challenged group (SP, 5 × 108 CFU/bird), (III) MccY-treated group (MccY, 20 mg/kg), and (Ⅳ) enrofloxacin-treated group (ENR, 50 mg/L). The results indicated that oral administration of MccY increased body weight and average daily gain (P < 0.05), reduced fecal and cecal S. Pullorum burden (P < 0.05), enhanced the thymus and bursa of Fabricius index and decreased the spleen and liver index (P < 0.05). Moreover, MccY increased the jejunal villus height, lowered the jejunal and ileal crypt depth (P < 0.05), and upregulated the expression of IL-4, IL-10, ZO-1, CLDN-1 in the jejunum and ileum, as well as CLDN-1 in the jejunum (P < 0.05). MccY increased the α-diversity (Simpson index) and the relative richness of Firmicutes, Bacteroidetes and probiotic flora (Faecalibacterium, etc.), while decreasing (P < 0.05) the relative richness of Proteobacteria and pathogenic flora (Salmonella and Klebsiella, etc.). In conclusion, oral administration of MccY promoted growth performance, reduced S. Pullorum colonization in the gut, improved anti-inflammatory and intestinal barrier function, and restored the balance of the gut microbiota, providing an antibiotic replacement for effective prevention and control of S. Pullorum.