In vitro surface properties of the newly recognized gastric pathogen Helicobacter pylori

Helicobacter pylori Biofilm Formation Is Differentially Affected by Common Culture Conditions, and Proteins Play a Central Role in the Biofilm Matrix

The concept of Helicobacter pylori biofilm formation is relatively new. To help provide a foundation for future biofilm studies, we characterized the biofilm formation ability of a common H. pylori lab strain, G27. The goal of this study was to evaluate biofilm formation by G27 in response to common culture conditions and to explore the biofilm matrix. Our results indicate that while various types of growth media did not dramatically affect biofilm formation, surface selection had a significant effect on the final biofilm mass. Furthermore, enzymatic assays and confocal microscopy revealed that proteins appear to be the primary structural component of the H. pylori extracellular matrix; extracellular DNA (eDNA) and polysaccharides were also present but appear to play a secondary role. Finally, we found that two well-characterized antibiofilm cationic peptides differentially affected early and late-stage biofilms. Together these results provide interesting avenues for future investigations that will seek to understand H. pylori biofilm formation.IMPORTANCE The study of H. pylori biofilm formation is still in its infancy. As such, there is great variability in how biofilm assays are performed across labs. While several groups have begun to investigate factors that influence H. pylori biofilm formation, it is not yet understood how H. pylori biofilm formation may vary based on commonly used conditions. These inconsistencies lead to difficulties in interpretation and comparison between studies. Here, we set out to characterize biofilm formation by a commonly available lab strain, G27. Our findings provide novel insight into optimal biofilm conditions, the biofilm matrix, and possible mechanisms to block or disrupt biofilm formation.

In Vitro Inhibition of Helicobacter pylori Growth by Redox Cycling Phenylaminojuglones

Infection by Helicobacter pylori increases 10 times the risk of developing gastric cancer. Juglone, a natural occurring 1,4-naphthoquinone, prevents H. pylori growth by interfering with some of its critical metabolic pathways. Here, we report the design, synthesis, and in vitro evaluation of a series of juglone derivatives, namely, 2/3-phenylaminojuglones, as potential H. pylori growth inhibitors. Results show that 5 out of 12 phenylaminojuglones (at 1.5 μg/mL) were 1.5-2.2-fold more active than juglone. Interestingly, most of the phenylaminojuglones (10 out of 12) were 1.1-2.8 fold more active than metronidazole, a known H. pylori growth inhibitor. The most active compound, namely, 2-((3,4,5-trimethoxyphenyl)amino)-5-hydroxynaphthalene-1,4-dione 7, showed significant higher halo of growth inhibitions (HGI = 32.25 mm) to that of juglone and metronidazole (HGI = 14.50 and 11.67 mm). Structural activity relationships of the series suggest that the nature and location of the nitrogen substituents in the juglone scaffold, likely due in part to their redox potential, may influence the antibacterial activity of the series.

Axisymmetric Drop Shape Analysis (ADSA): An Outline

Drop shape techniques for the measurement of interfacial tension are powerful, versatile and flexible. The shape of the drop/bubble depends on the balance between surface tension and external forces, e.g. gravity. This balance is reflected mathematically in the Laplace equation of capillarity. Axisymmetric Drop Shape Analysis (ADSA) is a commonly used drop shape technique. A streamlined version of the development of ADSA over the past several decades is presented to illustrate its validity and range of utility. Several configurations of interest will be considered and presented systematically. Shape and surface tension will be linked to a shape parameter based on proper concepts of differential geometry. The resulting shape parameter will be shown to allow determination of the range of applicability of such a drop shape method.

Preparation of epigallocatechin gallate-loaded nanoparticles and characterization of their inhibitory effects on Helicobacter pylori growth in vitro and in vivo

A variety of approaches have been proposed for overcoming the unpleasant side effects associated with antibiotics treatment of Helicobacter pylori (H. pylori) infections. Research has shown that epigallocatechin-3-gallate (EGCG), a major ingredient in green tea, has antibacterial activity for antiurease activity against H. pylori. Oral EGCG is not good because of its digestive instability and the fact that it often cannot reach the targeted site of antibacterial activity. To localize EGCG to H. pylori infection site, this study developed a fucose-chitosan/gelatin nanoparticle to encapsulate EGCG at the target and make direct contact with the region of microorganisms on the gastric epithelium. Analysis of a simulated gastrointestinal medium indicated that the proposed in vitro nanocarrier system effectively controls the release of EGCG, which interacts directly with the intercellular space at the site of H. pylori infection. Meanwhile, results of in vivo clearance assays indicated that our prepared fucose-chitosan/gelatin/EGCG nanoparticles had a significantly greater H. pylori clearance effect and more effectively reduced H. pylori-associated gastric inflammation in the gastric-infected mouse model than the EGCG solution alone.

Molecular mechanisms of late apoptotic/necrotic cell clearance

Phagocytosis serves as one of the key processes involved in development, maintenance of tissue homeostasis, as well as in eliminating pathogens from an organism. Under normal physiological conditions, dying cells (e.g., apoptotic and necrotic cells) and pathogens (e.g., bacteria and fungi) are rapidly detected and removed by professional phagocytes such as macrophages and dendritic cells (DCs). In most cases, specific receptors and opsonins are used by phagocytes to recognize and bind their target cells, which can trigger the intracellular signalling events required for phagocytosis. Depending on the type of target cell, phagocytes may also release both immunomodulatory molecules and growth factors to orchestrate a subsequent immune response and wound healing process. In recent years, evidence is growing that opsonins and receptors involved in the removal of pathogens can also aid the disposal of dying cells at all stages of cell death, in particular plasma membrane-damaged cells such as late apoptotic and necrotic cells. This review provides an overview of the molecular mechanisms and the immunological outcomes of late apoptotic/necrotic cell removal and highlights the striking similarities between late apoptotic/necrotic cell and pathogen clearance.

The sodium-dependent D-glucose transport protein of Helicobacter pylori

Helicobacter pylori is a gram-negative pathogenic microaerophile with a particular tropism for the mucosal surface of the gastric epithelium. Despite its obligatory microaerophilic character, it can metabolize D-glucose and/or D-galactose in both oxidative and fermentative pathways via a Na(+)-dependent secondary active transport, a glucokinase and enzymes of the pentose phosphate pathway. We have assigned the Na(+)-dependent transport of glucose to the protein product of the H. pylori 1174 gene. The gene was heterologously expressed in a glucose transport-deficient Escherichia coli strain, where transport activities of radiolabelled D-glucose, D-galactose and 2-deoxy-D-glucose were restored, consistent with the expected specificity of the hexose uptake system in H. pylori. D-mannose was also identified as a substrate. The HP1174 transport protein was purified and reconstituted into proteoliposomes, where sodium dependence of sugar transport activity was demonstrated. Additionally the tryptophan/tyrosine fluorescence of the purified protein showed quenching by 2-deoxy-D-glucose, D-mannose, D-glucose or D-galactose in the presence of sodium ions. This is the first reported purification and characterization of an active glucose transport protein member of the TC 2.1.7 subgroup of the Major Facilitator Superfamily, constituting the route for entry of sugar nutrients into H. pylori. A model is derived of its three-dimensional structure as a paradigm of the family.

A phase-variable capsule is involved in virulence of Campylobacter jejuni 81-176

Campylobacter jejuni strain 81-176 (HS36, 23) synthesizes two distinct glycan structures, as visualized by immunoblotting of proteinase K-digested whole-cell preparations. A site-specific insertional mutant in the kpsM gene results in loss of expression of a high-molecular-weight (HMW) glycan (apparent Mr 26 kDa to > 85 kDa) and increased resolution of a second ladder-like glycan (apparent Mr 26-50 kDa). The kpsM mutant of 81-176 is no longer typeable in either HS23 or HS36 antisera, indicating that the HMW glycan structure is the serodeterminant of HS23 and HS36. Both the kpsM-dependent HMW glycan and the kpsM-independent ladder-like structure appear to be capsular in nature, as both are attached to phospholipid rather than lipid A. Additionally, the 81-176 kpsM gene can complement a deletion in Escherichia coli kpsM, allowing the expression of an alpha2,8 polysialic acid capsule in E. coli. Loss of the HMW glycan in 81-176 kpsM also increases the surface hydrophobicity and serum sensitivity of the bacterium. The kpsM mutant is also significantly reduced in invasion of INT407 cells and reduced in virulence in a ferret diarrhoeal disease model. The expression of the kpsM-dependent capsule undergoes phase variation at a high frequency.

Adhesion, autoaggregation and hydrophobicity of 13 strains of Bifidobacterium longum

To identify bacterial traits related to adhesion ability in human bifidobacteria, 13 strains of Bifidobacterium longum isolated from human gastric juice and intestine were studied. Strains were tested for their capability to adhere to Caco-2 cells and classified as adhesive (Adh+) or non-adhesive (Adh-). Adh+ and Adh- strains were then investigated for their autoaggregation ability and surface hydrophobicity. Comparing the properties of Adh+ and Adh-, we observed that strains were able to adhere to cell monolayers if they autoaggregate and manifest a good degree of hydrophobicity as determined by microbial adhesion to hydrocarbons. These two traits could be used for preliminary screening to identify potentially adherent isolates.

Binding of Shigella to rat and human intestinal mucin

Invasion of epithelial cells by Shigella is an early step in their pathogenesis. Adherence is generally presumed to be a prerequisite for invasion. This study examined the possibility of intestinal mucins serving as initial binding sites for clinical isolates of S. boydii and S. sonnei. The interactions of Shigella with rat and human small intestinal and colonic mucin were investigated. In solid phase binding assays, [35S] labelled Shigella did not show any preferential binding to rat/human small intestinal mucin or to rat colonic mucin. On the other hand, Shigella bound specifically to human colonic mucin in a concentration-dependent manner. This specific binding to human colonic mucin was not by weak hydrophobic interactions and could not be attributed to the presence of contaminating glycolipids in the mucin preparation. The human colonic mucin receptor was sensitive to periodate treatment suggesting the involvement of the carbohydrate portion of the mucin. Reduction and alkylation of mucin enhanced adherence probably by exposing buried binding sites. The monosaccharides present in mucins were ineffective as hapten inhibitors as was the lectin wheat germ agglutinin suggesting that the mucin receptor is a more complex one. This study identifies, for the first time, the presence of a specific Shigella-binding site on the carbohydrate portion of human colonic mucin, which is not present in rat colonic mucin or in rat/human small intestinal mucin.

Cell surface glycosaminoglycans are not involved in the adherence of Helicobacter pylori to cultured Hs 198.St human gastric cells, Hs 746T human gastric adenocarcinoma cells, or HeLa cells

Hs 198.St cells (a line derived from normal human gastric tissue), Hs 746T cells (a line derived from human gastric adenocarcinoma), and HeLa cells were used together with 3H-labelled Helicobacter pylori, strain NCTC 11637 to determine if cell surface glycosaminoglycans could act as initial receptors for adherence of the bacteria. Although as much as 40% of the 3H-labelled bacteria adhered to monolayers of the cultured cells, removal of glycosaminoglycans by prior treatment of the cells with heparitinase, heparinase, or chondroitin ABC lyase had no effect in modifying the adherence. Prior addition of heparan sulfate, heparin, or chondroitin/dermatan sulfate to bacteria had no effect on adherence, nor were bacteria released when these same glycosaminoglycans or these same enzymes were added to cultures already containing adherent bacteria. These results indicated that neither heparan sulfate nor chondroitin/dermatan sulfate are involved as receptors in the initial adherence step of H. pylori to these cultured cells.

Comparison of Helicobacter pylori and attaching-effacing Escherichia coli adhesion to eukaryotic cells

Adhesion of Helicobacter pylori was reported previously to be morphologically identical to "attaching and effacing" Escherichia coli. Therefore, the aim of the present study was to define the adhesion phenotype of H. pylori LC-11 to HEp-2, KATO-III, HEL, and CHO tissue culture cells. By using both staining of F-actin with fluorescein-labeled phalloidin and ultrastructural analysis, diffuse bacterial adhesion to discrete microvillus-denuded regions of the plasma membrane was observed in each of the infected cell lines. However, strain LC-11 did not induce formation of F-actin adhesion pedestals on the eukaryotic cells. H. pylori was negative by colony blot hybridization with an E. coli attaching and effacing gene probe. Elevations in inositol triphosphates followed infection of HEp-2 cells with H. pylori (405% of control values +/- 147%; P < 0.05). To correlate the observed histopathology with expression of the H. pylori phosphatidylethanolamine receptor, a thin-layer chromatography overlay-binding assay was used to identify receptors in each of the cell lines. H. pylori adhered to eukaryotic cells regardless of the presence (HEp-2, KATO-III, and CHO cells) or absence (HEL cells) of the lipid receptor as detected under the assay conditions. However, in comparison to cell lines that possess the phosphatidylethanolamine receptor, HEL cells demonstrated less quantitative H. pylori binding. These findings suggest that mechanisms distinct from E. coli enteropathogens underlie the adhesion of H. pylori to mucosal surfaces. In addition to the phosphatidylethanolamine H. pylori receptor, another host factor(s) likely mediates the attachment of H. pylori to human eukaryotic cells.

Adherence of Helicobacter pylori to HEp-2 cells

The adherence of 25 strains of Helicobacter pylori was evaluated in HEp-2 cells. These bacterial isolates, obtained from Chilean patients with gastric disorders, were also tested for haemagglutination of human red blood cells. Adherence of HEp-2 cells was expressed as a common property of all strains, irrespective of whether the cultures were grown on semi-solid or in liquid media. Previous reports that haemagglutinating activity was present in cells grown only on semi-solid media were confirmed. Adherence to HEp-2 cells was suppressed when bacterial cells were pretreated with homologous or heterologous whole human serum, containing specific antibodies of H. pylori. Adherence remained unaltered when bacterial cells were similarly treated with normal serum lacking specific antibodies. These observations imply that adhesions are expressed in vivo and suggest that an adherence mechanism, not depending on the expression of specific haemagglutinin antigen, operates for H. pylori.

Cholesterol binding of Helicobacter pylori

H. pylori cells grown on cholesterol-free medium adsorb cholesterol from serum, egg yolk, and VDRL reagent. The binding of cholesterol does not influence the hydrophobicity of the cells. The haemagglutinating activity is slightly diminished. The cell-bound haemolytic activity is completely inhibited. The affinity of H. pylori for cholesterol probably acts as factor of chemotaxis and adherence.

Flocculation of venereal disease research laboratory reagent by Helicobacter pylori

Helicobacter pylori strains flocculated with Venereal Disease Research Laboratory (VDRL) reagent in a glass slide test. Other pathogenic bacterial and fungal strains were nonreactive. The specific VDRL reaction property of Helicobacter pylori indicates an affinity of the cells for lipoidal substances, and can be used as a diagnostic aid for species identification.