For submission IJMS:3414297_Songbo Li et al

Non-typhoidal salmonellosis (NTS) caused by multidrug-resistant (MDR) <i>Salmonella enterica</i> 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-<i>Salmonella</i> and immunomodulatory effects between viable (probiotics) and heat-killed (parabiotics) lactic acid bacteria <i>Lactiplantibacillus plantarum</i> KUNN19-2 (KUNN19-2), isolated from Thai-style fermented pork (Nham), against several strains of MDR <i>Salmonella</i>. Only viable KUNN19-2 and its cell-free supernatant directly inhibited <i>Salmonella</i> growth by spot-on lawn and agar well diffusion assays. A significant reduction in <i>Salmonella</i> 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 <i>Salmonella</i> and upregulated pro-inflammatory genes (<i>Mip-2</i>, <i>Nos2</i>) and anti-inflammatory gene (<i>IL10</i>) expression, with viable KUNN19-2 showing a more potent effect. Collectively, viable KUNN19-2 can directly inhibit <i>Salmonella</i> growth. However, viable and heat-killed KUNN19-2 can modulate gut immunity against <i>Salmonella</i> infection, suggesting that parabiotics KUNN19-2 may serve as an alternative treatment against MDR <i>Salmonella</i> through host immune modulation.