Probiotic, Paraprobiotic, and Postbiotic Activities of Lactiplantibacillus plantarum KUNN19-2 Against Non-Typhoidal Salmonella Serovars.

Non-typhoidal salmonellosis (NTS) caused by multidrug-resistant (MDR) Salmonella enterica is a significant public health concern worldwide. Probiotics offer a potential alternative to antibiotics in many infectious diseases, including NTS. However, using living bacteria raises safety concerns in clinical settings, especially in the immunocompromised host. This study compared the anti-Salmonella and immunomodulatory effects between viable (probiotics) and heat-killed (paraprobiotics) lactic acid bacteria Lactiplantibacillus plantarum KUNN19-2 (KUNN19-2), isolated from Thai-style fermented pork (Nham), against several strains of MDR Salmonella. Only viable KUNN19-2 and its cell-free supernatant directly inhibited Salmonella growth by spot-on lawn and agar well diffusion assays. A significant reduction in Salmonella numbers in the co-culture assay with viable KUNN19-2 was observed at 12-14 h after the incubation. Viable and heat-killed KUNN19-2 exhibited moderate adhesion to human colonic epithelium (T84) cells. Pretreatment with either form of KUNN19-2 enhanced macrophage (RAW264.7) phagocytic activity against Salmonella and upregulated pro-inflammatory genes (Mip-2 and Nos2) and anti-inflammatory gene (IL10) expression, with viable KUNN19-2 showing a more potent effect. Collectively, viable KUNN19-2 can directly inhibit Salmonella growth. However, viable and heat-killed KUNN19-2 can modulate gut immunity against Salmonella infection, suggesting that paraprobiotic KUNN19-2 may serve as an alternative treatment against MDR Salmonella through host immune modulation.