N-acyl homoserine lactonase attenuates the virulence of Salmonella typhimurium and its induction of intestinal damages in broilers

This study aimed to investigate the potential mitigating effects of N-acyl homoserine lactonase (AHLase) on the virulence of Salmonella typhimurium and its induction of intestinal damages in broilers. In vitro study was firstly conducted to examine if AHLase treatment could attenuate the virulence of S. typhimurium. Then, an in vivo experiment was performed by allocating 240 broiler chicks at 1 d old into 3 groups (8 replicates per group): negative control (NC), positive control (PC), and PC supplemented with 10,000 U/kg AHLase. All chicks except those in NC were orally challenged by S. typhimurium from 8 to 10 d of age. Parameters were measured on d 11 and 21. The results showed that treatment with 1 U/mL AHLase suppressed the biofilm-forming ability (including biofilm biomass, extracellular DNA secretion and biofilm formation-related gene expression), together with swarming motility and adhesive capacity of S. typhimurium. Supplemental 10,000 U/kg AHLase counteracted S. typhimurium-induced impairments (P < 0.05) in broiler growth performance (including final body weight, average daily gain and average daily feed intake) during either 1–11 d or 12–21 d, and increases (P < 0.05) in the indexes of liver, spleen and bursa of Fabricius on d 11, together with reductions (P < 0.05) in ileal villus height and its ratio to crypt depth on both d 11 and 21. AHLase addition also normalized the increased (P < 0.05) mRNA expression of ileal occludin on both d 11 and 21 in S. typhimurium-challenged broilers. However, neither S. typhimurium challenge nor AHLase addition altered (P > 0.05) serum diamine oxidase activity of broilers. Noticeably, S. typhimurium challenge caused little change in the mRNA expression of ileal inflammatory cytokines except for an increase (P < 0.05) in interleukin-8 expression on d 11, whereas AHLase addition normalized (P < 0.05) this change. In conclusion, AHLase treatment could attenuate the virulence and pathogenicity of S. typhimurium, thus contributing to alleviate S. typhimurium-induced growth retardation and intestinal damages in broilers.