The Prophylactic Protection of P. acidilactici M22 from Feline Milk on S. Typhimurium Infection in Mice

Breast milk is a major source of probiotics, particularly lactic acid bacteria (LAB), which are known to regulate the intestinal microbial community and exert antibacterial effects. However, little is known about the preventive effects of feline milk-derived LAB against Salmonella infection in vivo. In this study, a strain of Pediococcus acidilactici (M22) was isolated from feline milk and evaluated for its protective potential in C57BL/6 mice challenged with Salmonella Typhimurium SL1344 (VNP20009). Following oral administration of M22, mice were infected with S. Typhimurium, and protective efficacy was assessed through body weight changes, bacterial loads in tissues, histopathological examination of the colon, oxidative stress markers, cytokine profiles, and 16S rRNA gene sequencing of cecal microbiota. The results showed that pretreatment with M22 significantly reduced bacterial loads in the liver, spleen, and cecum compared with controls. M22 administration enhanced antioxidant capacity, alleviated infection-induced inflammation, and preserved intestinal barrier integrity by restoring villus morphology and upregulating tight junction proteins (ZO-1 and occludin). Microbiota analysis further revealed that M22 enriched short-chain fatty acid-producing beneficial taxa (e.g., lactic acid bacteria) while suppressing pro-inflammatory genera. Collectively, these findings provide scientific evidence that feline milk-derived P. acidilactici M22 is a safe and effective probiotic candidate. By enhancing gut health and host resistance to infection, M22 offers a promising strategy to improve companion animal health, reduce reliance on antibiotics, and mitigate zoonotic transmission of pathogens.