Non-typhoidal salmonellosis (NTS) caused by ingesting Salmonella enterica contaminated food or drink remains a major bacterial foodborne disease. Clinical outcomes of NTS range from self-limited gastroenteritis to life-threatening invasive NTS (iNTS). In this study, we isolated Salmonella spp. from the stool and blood of patients hospitalized at Maharaj Nakorn Chiang Mai Hospital, Chiang Mai, Thailand, between 2016–2021 (a total of 395 cases). Then, serovar Typhimurium and Enteritidis were identified and further characterized by multiplex PCR, and multi-locus sequence typing. Our data show that multidrug resistance (MDR) sequence type 34 (ST34) and ST11 are the predominant sequence types for serovars Typhimurium and Enteritidis, respectively. Most S. Typhimurium ST34 lacks spvB, and most S. Enteritidis ST11 harbor sseI, sodCI, rpoS and spvB genes. NTS can be found in a wide range of ages, and anemia could be a significant factor for S. Typhimurium infection (86.3%). Both S. Typhimurium (6.7%) and S. Enteritidis (25.0%) can cause iNTS in immunocompromised patients. S. Typhimurium conferred MDR phenotype higher than S. Enteritidis with multiple antibiotic resistance indexes of 0.22 and 0.04, respectively. Here, we characterized the important S. Typhimurium, S. Enteritidis, and human clinical factors of NTS within the region.

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.

Acute non-typhoidal salmonellosis (NTS) from non-typhoidal Salmonella remains a major cause of foodborne bacterial gastroenteritis, and non-antibiotic interventions are needed to combat multidrug-resistant NTS. Bioactive compounds from edible mushroom extracts have shown both direct and indirect antimicrobial activities on Salmonella. However, the variation in their antimicrobial activity could be due to several factors, including the extract’s form and strain. This study investigated the ability of crude exopolysaccharides (EPs) produced by Schizophyllum commune CMU-01 to limit Salmonella infection in vitro. Agar well diffusion and liquid culture were used to determine the direct anti-Salmonella activity of S. commune EPs, while the gentamicin protection assay and qPCR in human gut epithelium (T84 cells) and murine macrophages (RAW264.7 cells) were used to investigate its indirect (immunomodulatory) activity. Our data reveal that S. commune EPs do not confer the direct antimicrobial property against Salmonella. However, its immunomodulatory activity in two important components of the gut innate defense (the gut epithelium and macrophages) against Salmonella infection has been demonstrated. S. commune EPs reduce Salmonella gut epithelial cell invasion and activate macrophages toward M1 (inflammatory phenotype) polarization, resulting in the reduction in intracellular Salmonella burdens. Alterations in proinflammatory and anti-inflammatory cytokine gene expressions were also detected in S. commune EPs-treated cells. These findings suggest that the host innate immune response to fungal exopolysaccharides derived from S. commune CMU-01 favors reducing Salmonella proliferation within host cells by altering the expression levels of proinflammatory cytokines.