Lactiplantibacillus plantarum postbiotic protects against Salmonella infection in broilers via modulating NLRP3 inflammasome and gut microbiota

Salmonella infection is a major concern in poultry production which poses potential risks to food safety. Our previous study confirmed that Lactiplantibacillus plantarum (LP) postbiotic exhibited a strong antibacterial capacity on Salmonella in vitro. This study aimed to investigate the beneficial effects and underlying mechanism of LP postbiotic on Salmonella-challenged broilers. A total of 240 one-day-old male yellow-feathered broilers were pretreated with 0.8% MRS medium or 0.8% LP postbiotic (LP cell-free culture supernatant, LPC) in drinking water for 28 days, and then challenged with 109 CFU Salmonella enterica serotype Enteritidis (SE). Birds were sacrificed three days post infection. Results showed that LPC maintained the growth performance by increasing BW, ADG and ADFI in broilers under SE challenge. LPC significantly attenuated SE-induced intestinal mucosal damages. Specifically, it decreased the intestinal injury score, increased villus length and villus/crypt, regulated the expression of intestinal injury-related genes (Villin, MMP3, I-FABP), and enhanced tight junctions (ZO-1 and Claudin-1). SE infection caused a dramatic inflammatory response, as indicated by the up-regulated concentrations of IL-1β, IL-6, TNF-α, and the downregulation of IL-10, while LPC pretreatment markedly reversed this trend. We then found that LPC inhibited the activation of NLRP3 inflammasome by decreasing the gene expression of NLRP3, Caspase‐1, IL-lβ and IL-18. Furthermore, LPC suppressed NLRP3 inflammasome activation by inhibiting NF-κB signaling pathway (the reduced levels of TLR4, MyD88, IRAK4 and NF-κB). Finally, our results showed that LPC regulated gut microbiota by enhancing the percentage of Ligilactobacillus and decreasing Alistipes and Barnesiella. In summary, we found that LP postbiotic was effective to protect broilers against Salmonella infection, possibly through suppressing NLRP3 inflammasome and optimizing gut microbiota. Our study provides the potential of postbiotics on prevention of Salmonella infection in poultry.