Search

Shigella flexneri is a prevalent foodborne and waterborne pathogen that threatens human health. Our previous research indicated that the Lactiplantibacillus plantarum Y12 exopolysaccharide (L-EPS) potentially inhibited the pathogenicity of S. flexneri. The in vitro results of this study demonstrated that L-EPS effectively mitigated the symptoms induced by S. flexneri in HT-29 cells, including inhibited gene expression levels of IL-1β, IL-6, IL-8, TNF-α, TLR 2/4, and NOD1/2; decreased apoptosis ratio; and alleviated damage degree of intestinal barrier function (Zona occludens 1, Occludin, and Claudin-1). The in vivo results demonstrated that S. flexneri treated with L-EPS elicited mild adverse physiological manifestations, an inflammatory response, and tissue damage. The infection of S. flexneri caused significant alterations in the abundance of phylum (Firmicutes, Bacteroidota, Actinobacteriota, and Proteobacteria), family (Lachnospiraceae, Muribaculaceae, Rikenellaceae, Prevotellaceaea, Ruminococcaceae, and Lactobaillaceae), and genus (Escherichia Shigella and Lachnospirillaceae NK4A136 group) within the cecal microbiota. These changes were accompanied by perturbations in taurine and hypotaurine metabolism, tricarboxylic acid (TCA) cycle activity, arginine biosynthesis, and histidine metabolic pathways. However, intervention with L-EPS attenuated the dysbiosis of cecal microbiota and metabolic disturbances. In summary, our research suggested a potential application of L-EPS as a functional food additive for mitigating S. flexneri infection., Competing Interests: Declaration of competing interest The authors declared no potential conflicts of interest with respect to the research, authorship, and publication of this article., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Shigella is a specific enteric pathogen in humans, causing symptoms of bacterial dysentery. The biofilm formation of S. flexneri contributes to the emergence of multidrug resistance and facilitates the establishment of persistent chronic infections. This study investigated the regulatory effects of Lactiplantibacillus plantarum Y12 exopolysaccharide (L-EPS) on gene expression and its spatial hindrance effects in inhibiting the biofilm formation of S. flexneri. The transcriptome analysis revealed a significant impact of L-EPS on the gene expression profile of S. flexneri, with a total of 968 genes showing significant changes (507 up-regulated and 461 down-regulated). The significantly down-regulated KEGG metabolic pathway enriched in phosphotransferase system, Embden-Meyerhf-Parnas, Citrate cycle, Lipopolysaccharide biosynthesis, Cationic antimicrobial peptide resistance, Two-component system. Moreover, L-EPS significantly down-regulated the gene expression levels of fimbriae synthesis (fimF), lipopolysaccharide synthesis (lptE, lptB), anchor protein repeat domain (arpA), virulence factor (lpp, yqgB), antibiotic resistance (marR, cusB, mdtL, mdlB), heavy metal resistance (zraP), and polysaccharide synthesis (mtgA, mdoB, mdoC). The expression of biofilm regulator factor (bssS) and two-component system suppressor factor (mgrB) were significantly up-regulated. The RT-qPCR results indicated that a major component of L-EPS (L-EPS 2-1) exhibited the gene regulatory effect on the S. flexneri biofilm formation. Furthermore, electrophoresis and isothermal microtitration calorimetry demonstrated that the interaction between L-EPS 2-1 and eDNA is electrostatic dependent on the change in environmental pH, disrupting the stable spatial structure of S. flexneri biofilm. In conclusion, L-EPS inhibited the biofilm formation of S. flexneri through gene regulation and spatial obstruction effects., Competing Interests: Declaration of competing interest The authors declared no potential conflicts of interest with respect to the research, authorship, and publication of this article., (Copyright © 2023. Published by Elsevier B.V.)

In developing countries, Shigella flexneri is the most common enteric pathogen causing bacillary dysentery. Biofilm formation by S. flexneri can cause the emergence of antibiotic-resistant strains, which poses serious threats to food safety and human health. In this study, the effects of Lactobacillus plantarum 12 exopolysaccharides (L-EPSs) and S. flexneri exopolysaccharides (S-EPSs) on S. flexneri CMCC51574 biofilm formation were investigated. The results showed that L-EPS could decrease polysaccharide production in the extracellular polymeric matrix of S. flexneri and inhibit biofilm formation by S. flexneri L-EPS could decrease the minimum biofilm elimination concentration (MBEC) of antibiotics against S. flexneri biofilm and inhibit S. flexneri adhesion to and invasion into HT-29 cell monolayers, which might be ascribed to S. flexneri biofilm disturbance by L-EPS. In contrast, S-EPS exhibited the opposite effects compared to L-EPS. The monosaccharide composition analysis showed that L-EPS was composed of mannose, glucuronic acid, galactosamine, glucose, galactose, and xylose, with the molar ratio of 32.26:0.99:1.79:5.63:0.05:4.07, while S-EPS was composed of mannose, glucuronic acid, galactosamine, glucose, and galactose, with the molar ratio of 25.43:2.28:7.13:5.35. L-EPS was separated into the neutral polysaccharide L-EPS 1-1 and the acidic polysaccharide L-EPS 2-1 by ion-exchange chromatography and gel chromatography. L-EPS 2-1 exerted higher antibiofilm activity than L-EPS 1-1. The antibiofilm activity of L-EPS might be associated with its structure. IMPORTANCE S. flexneri is a widespread foodborne pathogen causing food contamination and responsible for food poisoning outbreaks related to various foods in developing countries. Not only has biofilm formation by S. flexneri been difficult to eliminate, but it has also increased the drug resistance of the strain. In the present study, it was demonstrated that L-EPSs secreted by Lactobacillus plantrum 12 could inhibit S. flexneri biofilm formation on, adhesion to, and invasion into HT-29 cells. Also, L-EPSs could decrease the minimum biofilm elimination concentration (MBEC) of the antibiotics used against S. flexneri biofilm. Therefore, L-EPSs were shown to be bioactive macromolecules with the potential ability to act against S. flexneri infections., (Copyright © 2020 American Society for Microbiology.)

Shigella flexneri is a waterborne and foodborne pathogen that can damage human health. The exopolysaccharides (S-EPS) produced by S. flexneri CMCC51574 were found to promote biofilm formation and virulence. In this research, the crude S-EPS produced by S. flexneri CMCC51574 were separated into three main different fractions, S-EPS 1-1, S-EPS 2-1, and S-EPS 3-1. The structure of the S -ESP 2-1 was identified by FT-IR, ion chromatography analysis, methylation analysis, and NMR analysis. The main chain of S-EPS 2-1 was α-Manp-(1 → 3)-α-Manp-[(1 → 2,6)-α-Manp]15-[(1 → 2)-Manf-(1→]8; there were two branched-chain R1 and R2 with a ratio of 4:1, R1: α-Manp-(1 → 6)- and R2: α-Manp-(1 → 6)- Glc-(1 → 6)- were linked with (1 → 2,6)-α-Manp. It was found that S-EPS 2-1 exhibited the highest promoting effect on biofilm formation of S. flexneri. The S-EPS 2-1 was identified to interact with extracellular DNA (eDNA) of S. flexneri , indicating that the S-EPS 2-1 was the specific polysaccharide in the spatial structure of biofilm formation. Our research found the important role of S-EPS in S. flexneri biofilm formation, which will help us to understand the underlining mechanisms of the biofilm formation and find effective ways to prevent S. flexneri biofilm infection. [ABSTRACT FROM AUTHOR]