Search

Escherichia coli and Salmonella are common pathogenic bacteria in human intestine, which can infect epithelial cells and cause diseases. Adhesion to intestinal tissue is the first step of pathogen infection. This work was to investigate the protective function of surface layer protein (SLP) from Lactobacillus casei fb05 against the harmful effects of E. coli and Salmonella on intestinal tissue (collagen and HT-29 cells). The SLP of L. casei fb05 was identified by transmission electron microscopy and SDS-PAGE. The purified SLP could reduce the adhesion of E. coli and Salmonella to collagen and HT-29 cells as observed by light microscope. The flow cytometry results showed that the L. casei fb05 SLP decreased the two pathogens-induced apoptosis of HT-29 cells by about 45%–49%. In addition, the activation of caspase-9 and caspase-3 caused by the two pathogens was significantly declined by the interference of the L. casei fb05 SLP. All the findings demonstrated that the L. casei fb05 SLP could decrease the deleterious effects of E. coli and Salmonella on intestinal tract in two ways: reducing pathogen adhesion and inhibiting pathogen-induced apoptosis. The potential of L. casei fb05 SLP in the treatment of intestinal diseases might be explored in this work. • L. casei surface layer protein (SLP) reduced the adhesion of pathogens to collagen. • L. casei SLP reduced the adhesion of pathogens to HT-29 cells. • L. casei SLP decreased the E. coli and Salmonella -induced apoptosis of HT-29 cells. [ABSTRACT FROM AUTHOR]

Background and purpose: E. coli O157:H7 is one of the intestinal pathogens that mediate serious damages in gastrointestinal track. The bacterium attachment in large intestine is mediated via some colonization factors mainly Type III secretion proteins that are involved in this process. Among these factors, EspA protein plays an important role in system foundation. The aim of this study was cloning and recombinant expression of EspA in order to achieve a stable construct for the protein production and using it as a vaccine candidate in future investigations. Materials and methods: Specific primers were designed by Oligo 7 software and gene amplification was performed by PCR technique on template DNA. Enzymatic digestion and ligation were done by restriction enzymes and T4 ligase enzyme, respectively. Recombinant expression of EspA was induced by IPTG following cloning confirmation. Protein confirmation was done by Western blotting analyze. Results: Results showed that cloning of espA in pET28a (+) vector was performed in an appropriate mode between expected sites. Also, EspA had good and remarkable recombinant expression after induction and the antibody used in western blotting could recognize EspA on nitrocellulose membrane. Conclusion: Stable recombinant construct containing espA gene was fabricated that showed appropriate recombinant expression of protein. So, this protein could be used in future studies as a vaccine candidate against E. coli O157:H7. [ABSTRACT FROM AUTHOR]

Tremendous advances have been made in mapping the complexity of the human gut microbiota in both health and disease states. These analyses have revealed that, rather than a constellation of individual species, a healthy microbiota comprises an interdependent network of microbes. The microbial and host interactions that shape both this network and the gastrointestinal environment are areas of intense investigation. Here we review emerging concepts of how microbial metabolic processes control commensal composition, invading pathogens, immune activation, and intestinal barrier function. We posit that all of these factors are critical for the maintenance of homeostasis and avoidance of overt inflammatory disease. A greater understanding of the underlying mechanisms will shed light on the pathogenesis of many diseases and guide new therapeutic interventions. [ABSTRACT FROM AUTHOR]

Enterotoxigenic Escherichia coli and Salmonella Typhimurium could adhere to epithelial tissue and destroy cell junctions, leading to intestinal inflammation and diarrhea. Lactobacillus could prevent the adhesion of pathogens to host cells and protect the mucosal barrier. The objective of this study was to investigate the protective effects of Lactobacillus amylophilus D14 on Caco-2 cells against the invasion of enterotoxigenic Escherichia coli K88 and Salmonella Typhimurium SL1344. We found that with a reduction in dextran permeability and an increase in transepithelial electrical resistance, L. amylophilus D14 could ameliorate the damage to cell integrity caused by pathogens. Furthermore, L. amylophilus D14 reduced the expression of phosphorylated extracellular signal-regulated protein kinase and phospho-c-jun N-terminal kinase, and it decreased the secretion of IL-8. The abilities of the Lactobacillus to protect the cell junctions were then evaluated on Caco- 2 cells. Increased expression and amelioration distribution of tight junction proteins (zonula occludens-1, claudin-1, and E-cadherin) were observed when the cells were cocultured with pathogens and Lactobacillus simultaneously. Lactobacillus amylophilus D14 may influence the mitogen-activated protein kinase pathway to regulate the correct assembly of the tight junction and adherens junction, protecting the cell junctions and mucosal barrier damaged by enterotoxigenic E. coli K88 or Salmonella Typhimurium SL1344 infection. [ABSTRACT FROM AUTHOR]

Campylobacter jejuni is the most common bacterial cause of enterocolitis in humans, leading to diarrhoea and chronic extraintestinal diseases. Although probiotics are effective in preventing other enteric infections, beneficial microorganisms have not been extensively studied with C. jejuni. The aim of this study was to delineate the ability of selected probiotic Lactobacillus strains to reduce epithelial cell invasion by C. jejuni. Human colon T84 and embryonic intestine 407 epithelial cells were pretreated with Lactobacillus strains and then infected with two prototypic C. jejuni pathogens. Lactobacillus helveticus, strain R0052 reduced C. jejuni invasion into T84 cells by 35–41%, whereas Lactobacillus rhamnosus R0011 did not reduce pathogen invasion. Lactobacillus helveticus R0052 also decreased invasion of one C. jejuni isolate (strain 11168) into intestine 407 cells by 55%. Lactobacillus helveticus R0052 adhered to both epithelial cell types, which suggest that competitive exclusion could contribute to protection by probiotics. Taken together, these findings indicate that the ability of selected probiotics to prevent C. jejuni-mediated disease pathogenesis depends on the pathogen strain, probiotic strain and the epithelial cell type selected. The data support the concept of probiotic strain selectivity, which is dependent on the setting in which it is being evaluated and tested. [ABSTRACT FROM AUTHOR]