A novel vulture-derived Lactobacillus agilis LA-V4 protects broilers from Salmonella Typhimurium by coordinating gut microbiota homeostasis, mucosal barrier integrity, and hepatic autophagic defense
Salmonella Typhimurium (S. Typhimurium) is a major enteric pathogen in poultry production, causing substantial economic losses and posing a serious public health threat through the contamination of animal-derived food products. Although probiotics are increasingly recognized as promising alternatives to antibiotics for controlling Salmonella infection, their mechanistic basis of protection remains insufficiently defined. Here, we evaluated the probiotic efficacy of Lactobacillus agilis L.A-V4, a stress-tolerant strain isolated from vulture feces, in healthy Arbor Acres broilers and in a prophylactic model of S. Typhimurium infection. In healthy birds, L.A-V4 supplementation enhanced mucosal immune responses and appeared to alleviate hepatic metabolic stress associated with rapid early growth. In S. Typhimurium-challenged broilers, L.A-V4 markedly improved intestinal barrier integrity by upregulating the tight junction proteins ZO-1 and Occludin. Moreover, L.A-V4 significantly reduced cecal Salmonella colonization and corrected infection-associated microbial dysbiosis, notably by suppressing the overrepresentation of Firmicutes-related taxa such as Lachnospiraceae and Erysipelotrichales while enriching Lactobacillus and key short-chain fatty acid-producing genera, including v9d2013_group, Phascolarctobacterium, and Fournierella. In hepatic tissue, L.A-V4 restored autophagic activity, as reflected by increased LC3-II and Beclin1 expression and reduced p62 accumulation. Taken together, our findings identify L. agilis L.A-V4 as a novel probiotic candidate that protects broilers against S. Typhimurium infection through coordinated regulation of the gut microbiota, intestinal barrier function, and hepatic autophagic responses.