Systemic Lectin-Glycan Interaction of Pathogenic Enteric Bacteria in the Gastrointestinal Tract

Microorganisms, such as bacteria, viruses, and fungi, and host cells, such as plants and animals, have carbohydrate chains and lectins that reciprocally recognize one another. In hosts, the defense system is activated upon non-self-pattern recognition of microbial pathogen-associated molecular patterns. These are present in Gram-negative and Gram-positive bacteria and fungi. Glycan-based PAMPs are bound to a class of lectins that are widely distributed among eukaryotes. The first step of bacterial infection in humans is the adhesion of the pathogen's lectin-like proteins to the outer membrane surfaces of host cells, which are composed of glycans. Microbes and hosts binding to each other specifically is of critical importance. The adhesion factors used between pathogens and hosts remain unknown; therefore, research is needed to identify these factors to prevent intestinal infection or treat it in its early stages. This review aims to present a vision for the prevention and treatment of infectious diseases by identifying the role of the host glycans in the immune response against pathogenic intestinal bacteria through studies on the lectin-glycan interaction.

Biocompatible Nanocomposite Tailored to Endure the Gastric Niche Renders Effective in Vitro Elimination of Intestinal Pathogenic Bacteria and Supports Adhesion by Beneficial Bacteria

Bacteriocins produced by lactic acid bacteria (LAB) are potent therapeutic arsenals for targeting gastrointestinal pathogens and a promising alternative to antibiotics, because of their selective activity and reduced propensity to trigger collateral damage to the beneficial gut microbes. However, proteolytic inactivation in the gastric niche renders bacteriocins ineffective. The present study addresses this challenge and demonstrates that a biocompatible milk protein fraction can be leveraged to generate a robust nanocargo, which renders protection from proteolysis in the gastric milieu and facilitates delivery of the encapsulated bacteriocin pediocin. In a simulated gastric transit experiment, pediocin-loaded milk protein nanocomposite (Ped-MNC) could render a 3.0 log reduction in the viability of model gastrointestinal pathogens. Ped-MNC is nontoxic to cultured human intestinal cells (HT-29 cells) and effectively abrogates pathogenic bacteria adhering onto intestinal cells. In a combinatorial regimen, Ped-MNC and the beneficial LAB Lactobacillus plantarum DF9 could substantially reduce the levels of the pathogen Enterococcus faecalis MTCC 439 adhering onto HT-29 cells and interestingly the nanocomposite does not hinder adhesion of intestinal cells by the beneficial LAB. The developed nanocomposite holds promise as a niche specific therapeutic for selective mitigation of intestinal pathogens.

Characteristics of microbial communities and intestinal pathogenic bacteria for migrated Larus ridibundus in southwest China

Larus ridibundus, a migratory wild bird, has become one of the most popular gull species in southwest China in recent years. There has been no information on the gut microbiota and intestinal pathogenic bacteria configuration in wild L. ridibundus, even though the public are in close contact with this bird. In this study, 16S rRNA amplicon‐sequencing methods were used to describe the microbial community structure and intestinal pathogenic bacteria were isolated to identify their characteristics. The taxonomic results revealed that Firmicutes (86%), Proteobacteria (10%), and Tenericutes (3%) were the three most abundant phyla in the gut of L. ridibundus. Enterococcaceae, Enterobacteriaceae, and Mycoplasmataceae were the most predominant families, respectively. The number of operational taxonomic units (OTUs), the richness estimates and diversity indices of microbiota, was statistically different (p < 0.05). However, beta diversity showed that no statistical significance (p > 0.05) between all the fecal samples. The most frequently isolated intestinal pathogenic bacteria from L. ridibundus were enteropathogenic Escherichia coli (32%) and Salmonella (21%). Pulsed‐field gel electrophoresis (PFGE) results of Salmonella species revealed a high degree of similarity between isolates, which was not observed for other species. None of the potentially pathogenic isolates were identical to human‐isolated counterparts suggesting that there was little cross‐infection between humans and gulls, despite close proximity. In brief, this study provided a baseline for future L. ridibundus microbiology analysis, and made an understanding of the intestinal bacterial community structure and diversity.