Adhesins Research Articles

Lactate causes downregulation of Helicobacter pylori adhesin genes sabA and labA while dampening the production of proinflammatory cytokines

Chronic inflammation induced by Helicobacter pylori is strongly associated with gastric cancer development, which is influenced by both bacterial virulence and host genetics. The sialic acid-binding adhesin SabA and the MUC5AC-binding adhesin LabA are important H. pylori virulence factors that facilitate adhesion of the bacterium, which is a crucial step in colonization. Lactate utilization has been reported to play a key role in the pathogenicity of different bacterial species. However, this is poorly understood in H. pylori. In this study, we investigated the effect of lactate on H. pylori adhesin gene expression and the regulation of host inflammatory cytokines. We show that the bacterial adhesins SabA and LabA were downregulated at the transcriptional level during incubation of H. pylori with lactate. Downregulation of sabA required the involvement of the two-component system ArsRS, while labA was regulated via the CheA/CheY system, indicating differences in the regulation of these genes in response to lactate. The levels of the proinflammatory cytokines TNF and IL-6 in H. pylori-stimulated macrophages were reduced when lactate was present. Interestingly, glucose did not prevent the secretion of these cytokines. Taken together, our data suggest that lactate affects H. pylori adhesin gene expression and the host response upon infection.

240 Nutritional Intervention to Improve Carbohydrate Utilization and gut Health in Pigs

Abstract In swine production, using feed antibiotics as antimicrobial growth promotants has been reduced; thus, feed alternatives to manage gut health are required. Dietary fiber, resistant starch, oligosaccharides, and exopolysaccharides are carbohydrate structures and are nutritional tools that may enhance gut health in pigs. Dietary carbohydrates may have a role to alleviate diarrheal diseases including in pigs post-weaning but also reduce constipation in sows. Antibiotics are hypothesized to influence gut health via modulation of intestinal microbial profiles; fermentation and intestinal inflammation are considered important mechanisms. Dietary fiber sources differ in 2 key properties: fermentability and solubility. Rapid fermentation of fiber and oligosaccharides is associated with changes in microbial profiles and increased metabolite production. Recently, microbial composition was hypothesized to be less important and combined output of metabolites should be the focus. Fiber properties may also manipulate retention time and physico-chemical properties of the undigested residue; hence, non-fermentable insoluble fiber may prevent constipation in sows. Starch is mostly digested and absorbed as glucose. However, resistant starch is not digested and acts as insoluble but fermentable fiber and has unique properties, because it specifically increases intestinal abundance of bifidobacteria, which are associated with improved gut health. Using crop breeding, feed processing, and feed additives, the structure of fiber and starch can be altered thereby changing its degradation kinetics and affecting its utilization as energy source and its prebiotic activity. Finally, exopolysaccharides from Limosilactobacillus reuteri and unique oligosaccharides may serve as receptor analogues for pathogenic bacteria, e.g., enterotoxigenic Escherichia coli (ETEC). These receptor analogues block lectin domains of bacterial adhesins and thus prevent adherence of pathogens to the gut wall, thereby avoiding initiation of post-weaning diarrhea. In conclusion, dietary carbohydrates are important energy sources but may also provide important solutions to maintain gut health in pigs.

The XadA Trimeric Autotransporter Adhesins in Xylella fastidiosa Differentially Contribute to Cell Aggregation, Biofilm Formation, Insect Transmission and Virulence to Plants.

Surface adhesion strategies are widely employed by bacterial pathogens during establishment and systemic spread in their host. A variety of cell-surface appendages such as pili, fimbriae, and afimbrial adhesins are involved in these processes. The phytopathogen Xylella fastidiosa employs several of these structures for efficient colonization of its insect and plant hosts. Among the adhesins encoded in the X. fastidiosa genome, three afimbrial adhesins, XadA1, Hsf/XadA2, and XadA3, are predicted to be trimeric autotransporters with a C-terminal YadA-anchor membrane domain. We analyzed the individual contributions of XadA1, XadA2, and XadA3 to various cellular behaviors both in vitro and in vivo. Using isogenic X. fastidiosa mutants, we found that cell-cell aggregation and biofilm formation were severely impaired in the absence of XadA3. No significant reduction of cell-surface attachment was found with any mutant under flow conditions. Acquisition by insect vectors and transmission to grapevines were reduced in the XadA3 deletion mutant. While the XadA3 mutant was hypervirulent in grapevines, XadA1 or XadA2 deletion mutants conferred lower disease severity than the wild-type strain. This insight of the importance of these adhesive proteins and their individual contributions to different aspects of X. fastidiosa biology should guide new approaches to reduce pathogen transmission and disease development. [Formula: see text] Copyright © 2022 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.

Prevention of Initial Bacterial Attachment by Osteopontin and Other Bioactive Milk Proteins.

A considerable body of work has studied the involvement of osteopontin (OPN) in human physiology and pathology, but comparably little is known about the interaction of OPN with prokaryotic cells. Recently, bovine milk OPN has been proposed as a therapeutic agent to prevent the build-up of dental biofilms, which are responsible for the development of caries lesions. Bioactive milk proteins are among the most exciting resources for caries control, as they hamper bacterial attachment to teeth without affecting microbial homeostasis in the mouth. The present work investigated the ability of OPN to prevent the adhesion of three dental biofilm-forming bacteria to saliva-coated surfaces under shear-controlled flow conditions in comparison with the major milk proteins α-lactalbumin, β-lactoglobulin, αs1-casein, β-casein and κ-casein, as well as crude milk protein. OPN was the most effective single protein to reduce the adhesion of Actinomyces naeslundii, Lactobacillus paracasei subsp. paracasei and Streptococcus mitis. β-casein and crude milk protein also had a pronounced effect on all three species, which suggests binding to different microbial surface structures rather than the blocking of a specific bacterial adhesin. Bioactive milk proteins show potential to delay harmful biofilm formation on teeth and hence the onset of biofilm-related oral disease.

Molecular Targets for Antibody-Based Anti-Biofilm Therapy in Infective Endocarditis.

Infective endocarditis (IE) is a heart disease caused by the infection of heart valves, majorly caused by Staphilococcus aureus. IE is initiated by bacteria entering the blood circulation in favouring conditions (e.g., during invasive procedures). So far, the conventional antimicrobial strategies based on the usage of antibiotics remain the major intervention for treating IE. Nevertheless, the therapeutic efficacy of antibiotics in IE is limited not only by the bacterial drug resistance, but also by the formation of biofilms, which resist the penetration of antibiotics into bacterial cells. To overcome these drawbacks, the development of anti-biofilm treatments that can expose bacteria and make them more susceptible to the action of antibiotics, therefore resulting in reduced antimicrobial resistance, is urgently required. A series of anti-biofilm strategies have been developed, and this review will focus in particular on the development of anti-biofilm antibodies. Based on the results previously reported in the literature, several potential anti-biofilm targets are discussed, such as bacterial adhesins, biofilm matrix and bacterial toxins, covering their antigenic properties (with the identification of potential promising epitopes), functional mechanisms, as well as the antibodies already developed against these targets and, where feasible, their clinical translation.

Development and applications of sialoglycan-recognizing probes (SGRPs) with defined specificities: exploring the dynamic mammalian sialoglycome.

Glycans that are abundantly displayed on vertebrate cell surface and secreted molecules are often capped with terminal sialic acids (Sias). These diverse 9-carbon-backbone monosaccharides are involved in numerous intrinsic biological processes. They also interact with commensals and pathogens, while undergoing dynamic changes in time and space, often influenced by environmental conditions. However, most of this sialoglycan complexity and variation remains poorly characterized by conventional techniques, which often tend to destroy or overlook crucial aspects of Sia diversity and/or fail to elucidate native structures in biological systems, i.e. in the intact sialome. To date, in situ detection and analysis of sialoglycans has largely relied on the use of plant lectins, sialidases, or antibodies, whose preferences (with certain exceptions) are limited and/or uncertain. We took advantage of naturally evolved microbial molecules (bacterial adhesins, toxin subunits, and viral hemagglutinin-esterases) that recognize sialoglycans with defined specificity to delineate 9 classes of sialoglycan recognizing probes (SGRPs: SGRP1-SGRP9) that can be used to explore mammalian sialome changes in a simple and systematic manner, using techniques common in most laboratories. SGRP candidates with specificity defined by sialoglycan microarray studies were engineered as tagged probes, each with a corresponding nonbinding mutant probe as a simple and reliable negative control. The optimized panel of SGRPs can be used in methods commonly available in most bioscience labs, such as ELISA, western blot, flow cytometry, and histochemistry. To demonstrate the utility of this approach, we provide examples of sialoglycome differences in tissues from C57BL/6 wild-type mice and human-like Cmah-/- mice.

The 32 kDa Outer Membrane Proteins of Klebsiella pneumoniae Acts as A Bacterial Adhesin

Klebsiella pneumoniae is a bacterium that often causes infection in the human body. At present K. pneumoniae can resist some of the antibiotics it has associated with modification of one of the virulence factors possessed by K. pneumoniae. One virulence factor of K. pneumoniae as pathogen bacteria is Outer Membrane Protein (OMP). The study of adhesin factors in K. pneumoniae involving hemagglutinin and adhesin proteins that have been found in the OMP 20 kDa and 40 kDa, but there is still no research that discusses the role of 32 kDa OMP as a hemagglutinin protein and adhesin. The purpose of this study is to determine the role of 32 kDa outer membrane of K. pneumoniae as hemagglutinin and adhesin proteins. After isolation of Outer Member Protein (OMP) from the K. pneumoniae, which then carried out a hemagglutination test using mice erythrocyte cells and adhesion test using mice enterocyte cells. The results of the hemagglutination test using mice erythrocyte cells obtained the highest hemagglutination titer for the molecular weight of 32 kDa in titers 1/4. The adhesion index with dilution titer has a significant relationship, with a conversion coefficient of 0,813 which means the dilution titer with the OMP adhesion index has a strong relationship with the direction of a positive relationship. The regression test results obtained an R-value of 0,813 which shows a strong relationship, while the R2 value is 66.1%. Conclusion in this study is 32 kDa outer membrane proteins of K. pneumoniae acts as a bacterial adhesin.

Heterologous production of the adhesin LIC13411 from pathogenic Leptospira facilitates binding of non-pathogenic Leptospira in vitro and in vivo.

Leptospirosis is an important cause of morbidity and mortality worldwide. Disease severity ranges from asymptomatic colonization to widespread hemorrhage and multiorgan dysfunction. The causative agents, Leptospira spp., are zoonotic Gram-negative spirochetes. One important step in pathogenesis is binding of bacterial adhesins to host components. Previously our laboratory identified two L. interrogans candidate adhesins, LIC11574 and LIC13411, that bind to VE-cadherin in vitro. In the current study, we demonstrate the ability of two strains of pathogenic L. interrogans to disrupt the localization of VE-cadherin, a protein important to maintaining inter-endothelial junctions. Purified MBP-LIC11574 and MBP-LIC13411 bind human dermal microvascular endothelial cells in a pattern reminiscent of VE-cadherin, but do not disrupt VE-cadherin localization. Genes encoding the candidate adhesins from pathogenic Leptospira were cloned in an overexpression vector and introduced into non-pathogenic L. biflexa, creating gain-of-function strains producing LIC11574 or LIC13411. Protein production and localization to the outer membrane were confirmed by Triton X-114 fractionation. Although these strains do not disrupt VE-cadherin localization, production of LIC13411 increases binding of non-pathogenic Leptospira to human endothelial cells and specifically to VE-cadherin. In a short-term murine model of infection, LIC13411 production led to increased burdens of the non-pathogen in the lung, liver, kidney, and bladder. These data confirm the role of LIC13411 as an adhesin in Leptospira spp. and implicate it in dissemination to multiple organs. Importantly, anti-adhesin therapy has been shown to have many benefits over classical antibiotics. Taken together, this work provides novel insight into the pathogenesis of Leptospira spp. and identifies LIC13411 as a potential prophylactic and therapeutic target.

The In Vitro Replication Cycle of Achromobacter xylosoxidans and Identification of Virulence Genes Associated with Cytotoxicity in Macrophages.

ABSTRACTAchromobacter xylosoxidans is an opportunistic pathogen implicated in a wide variety of human infections including the ability to colonize the lungs of cystic fibrosis (CF) patients. The role of A. xylosoxidans in human pathology remains controversial due to the lack of optimized in vitro and in vivo model systems to identify and test bacterial gene products that promote a pathological response. We have previously identified macrophages as a target host cell for A. xylosoxidans-induced cytotoxicity. By optimizing our macrophage infection model, we determined that A. xylosoxidans enters macrophages and can reside within a membrane bound vacuole for extended periods of time. Intracellular replication appears limited with cellular lysis preceding an enhanced, mainly extracellular replication cycle. Using our optimized in vitro model system along with transposon mutagenesis, we identified 163 genes that contribute to macrophage cytotoxicity. From this list, we characterized a giant RTX adhesin encoded downstream of a type one secretion system (T1SS) that mediates bacterial binding and entry into host macrophages, an important first step toward cellular toxicity and inflammation. The RTX adhesin is encoded by other human isolates and is recognized by antibodies present in serum isolated from CF patients colonized by A. xylosoxidans, indicating this virulence factor is produced and deployed in vivo. This study represents the first characterization of A. xylosoxidans replication during infection and identifies a variety of genes that may be linked to virulence and human pathology.IMPORTANCE Patients affected by CF develop chronic bacterial infections characterized by inflammatory exacerbations and tissue damage. Advancements in sequencing technologies have broadened the list of opportunistic pathogens colonizing the CF lung. A. xylosoxidans is increasingly recognized as an opportunistic pathogen in CF, yet our understanding of the bacterium as a contributor to human disease is limited. Genomic studies have identified potential virulence determinants in A. xylosoxidans isolates, but few have been mechanistically studied. Using our optimized in vitro cell model, we identified and characterized a bacterial adhesin that mediates binding and uptake by host macrophages leading to cytotoxicity. A subset of serum samples from CF patients contains antibodies that recognize the RTX adhesion, suggesting, for the first time, that this virulence determinant is produced in vivo. This work furthers our understanding of A. xylosoxidans virulence factors at a mechanistic level.

Urinary Tract Infections Caused by Uropathogenic Escherichia coli Strains-New Strategies for an Old Pathogen.

Urinary tract infections (UTIs) are among the most common infections worldwide. Uropathogenic Escherichia coli (UPECs) are the main causative agent of UTIs. UPECs initially colonize the human host adhering to the bladder epithelium. Adhesion is followed by the bacterial invasion of urothelial epithelial cells where they can replicate to form compact aggregates of intracellular bacteria with biofilm-like properties. UPEC strains may persist within epithelial urothelial cells, thus acting as quiescent intracellular bacterial reservoirs (QIRs). It has been proposed that host cell invasion may facilitate both the establishment and persistence of UPECs within the human urinary tract. UPEC strains express a variety of virulence factors including fimbrial and afimbrial adhesins, invasins, iron-acquisition systems, and toxins, which cooperate to the establishment of long lasting infections. An increasing resistance rate relative to the antibiotics recommended by current guidelines for the treatment of UTIs and an increasing number of multidrug resistant UPEC isolates were observed. In order to ameliorate the cure rate and improve the outcomes of patients, appropriate therapy founded on new strategies, as alternative to antibiotics, needs to be explored. Here, we take a snapshot of the current knowledge of coordinated efforts to develop innovative anti-infective strategies to control the diffusion of UPECs.

VlsE, the nexus for antigenic variation of the Lyme disease spirochete, also mediates early bacterial attachment to the host microvasculature under shear force.

Hematogenous dissemination is a critical step in the evolution of local infection to systemic disease. The Lyme disease (LD) spirochete, which efficiently disseminates to multiple tissues, has provided a model for this process, in particular for the key early event of pathogen adhesion to the host vasculature. This occurs under shear force mediated by interactions between bacterial adhesins and mammalian cell-surface proteins or extracellular matrix (ECM). Using real-time intravital imaging of the Lyme spirochete in living mice, we previously identified BBK32 as the first LD spirochetal adhesin demonstrated to mediate early vascular adhesion in a living mouse; however, deletion of bbk32 resulted in loss of only about half of the early interactions, suggesting the existence of at least one other adhesin (adhesin-X) that promotes early vascular interactions. VlsE, a surface lipoprotein, was identified long ago by its capacity to undergo rapid antigenic variation, is upregulated in the mammalian host and required for persistent infection in immunocompetent mice. In immunodeficient mice, VlsE shares functional overlap with OspC, a multi-functional protein that displays dermatan sulfate-binding activity and is required for joint invasion and colonization. In this research, using biochemical and genetic approaches as well as intravital imaging, we have identified VlsE as adhesin-X; it is a dermatan sulfate (DS) adhesin that efficiently promotes transient adhesion to the microvasculature under shear force via its DS binding pocket. Intravenous inoculation of mice with a low-passage infectious B. burgdorferi strain lacking both bbk32 and vlsE almost completely eliminated transient microvascular interactions. Comparative analysis of binding parameters of VlsE, BBK32 and OspC provides a possible explanation why these three DS adhesins display different functionality in terms of their ability to promote early microvascular interactions.

Molecular docking reveals Chitosan nanoparticle protection mechanism for dentin against Collagen-binding bacteria

The medical application of chitosan (Cs) has been for about half a century, but the molecular mechanism has not been elucidated yet. This study is to explore the antibacterial mechanism of chitosan nanoparticles (Csnp) in dentin at the atomic resolution level. Extracted tooth specimen was prepared in three groups: A. control group; B. Csnp treatment under ultrasonic agitation (UA); C. Csnp treatment without UA. A scanning electron microscope (SEM) was used to observe the Csnp distribution on the dentin surface. The incubations of Enterococcus faecalis (E. faecalis) were performed. Further, we explored the protection mechanism of chitosan polymers to collagen type I, using molecular docking technique and crystal structure superimposition analysis. We revealed that Csnp under UA was evenly distributed on the dental surface and the Csnp-pretreated dentin had great antibacterial activity for E. faecalis. Our work demonstrated that Csnp occupied the grooves of the triple-helical collagen surface, strengthened by crosslinking, and interfered with the bond of collagen adhesin through steric hindrance effect and interrupting hydrophobic interaction. Csnp protects dentin against E. faecalis by interacting and crosslinking with collagen type I and prevents bacterial collagen adhesin binding through steric hindrance effect and interrupting hydrophobic interaction.Graphical abstract

Serial crystallography and kinetics reveal how the FimH bacterial lectin tweaks between mono‐ and multivalent binding of high‐mannose N‐glycans

BackgroundThe lectin domain of the fimbrial adhesin FimH from Escherichia coli recognizes with the highest affinity and in seemingly monovalent fashion oligomannosides‐3 and ‐5 N‐glycans. This happens with a high affinity (Kd=20 nM) because the alpha1,3‐linked arm remains free from any further alpha1,2‐mannose substitution. The latter causes an at least 10‐fold affinity loss in creating the oligomannose‐6 N‐glycan (1).MethodsThe binding of FimH to pauci‐ and oligomannoside‐containing N‐glycans and similarly glycosylated proteins, as well as its dimannoside endings Manalpha1,2, Manalpha1,3 and Manalpha1,6, have been profiled using the FimH Lectprofile kit (GlycoDiag, Applied Glycomics, France) and a newly designed paucimannose‐containing glycan array. The kinetics of binding, ka and kd, were analysed using surface plasmon resonance and compared with earlier incomplete data (2).ResultsMono‐ and multivalent binding were found in co‐crystal structures of the FimH lectin domain with alpha1,6‐fucosylated oligomannose‐3 and with oligoannose‐6, respectively. The kinetics of binding indicate that once alpha1,2‐linked mannose comes into play, the complexes are not so stable, as previously also measured using calorimetry (3), and accompanied with a high dissociation constant. Molecular dynamics simulations further support that it is not the total interaction energy that determines the final retained complex (metastable complexes), but the kinetics of interaction with the three possible dimannoside endings.ConclusionsKinetics and stability of the complexes drive the most favoured arrangement, via either a unique or multivalent interaction, between the N‐glycan and the FimH protein in the crystal.References :(1) Bouckaert, J., Mackenzie, J., de Paz, J. L., Chipwaza, B., Choudhury, D., Zavialov, A., Mannerstedt, K., Anderson, J., Pierard, D., Wyns, L., Seeberger, P. H., Oscarson, S., De Greve, H., Knight, S. D. (2006) The affinity of the FimH fimbrial adhesin is receptor‐driven and quasi‐independent of Escherichia colipathotypes. Molecular Microbiology 61, 1556‐1568(2) Sauer, M. M., Jakob, R. P., Luber, T., Canonica, F., Navarra, G., Ernst, B., Maier, T., Glockshuber, R. (2019) Binding of the bacterial adhesin FimH to its natural, multivalent high‐mannose type glycan targets. J Am Chem Soc 141, 936‐944(3) Dumych, T., Bridot, C., Gouin, S. G., Paryzhak, S., Szunerits, S., Bilyy, R., Bouckaert, J., (2018) A novel integrated way for deciphering the glycan code for the FimH lectin. Molecules 23, 2794

29 Nutritional Interventions for Intestinal Health of Nursery Pigs: Carbohydrates

Abstract In swine production, using feed antibiotics as antimicrobial growth promotants has been reduced; thus, feed alternatives to manage gut health are required to prevent post-weaning diarrhea. Dietary fiber, resistant starch, oligosaccharides, and exopolysaccharides are carbohydrates that together with glycoproteins are nutritional tools that may be part of managing gut health in pigs. Antibiotics are hypothesized to influence gut health via modulation of intestinal microbial profiles; fermentation and intestinal inflammation are considered important mechanisms. Dietary fiber is an alternative, but its sources differ in at least 2 key properties: fermentability and viscosity. Rapid fermentation of fiber and oligosaccharides is associated with changes in microbial profiles and increased metabolite production. Recently, microbial composition was hypothesized to be less important and combined output of metabolites should be the focus. Increased viscosity has been associated with increased gut content of virulence factors that are linked with diarrhea. Fiber properties may also manipulate retention time and physico-chemical properties of the undigested residue. Starch is mostly digested and absorbed as glucose. However, resistant starch is not digested and acts as fermentable fiber but has unique properties, because it specifically increases intestinal abundance of bifidobacteria that are associated with improved gut health. Feed ingredients and some feed additives influence kinetics of fermentation and have prebiotic activity. Their kinetics of fermentation should be quantified so that it can be considered in feed formulation. Finally, exopolysaccharides from Limosilactobacillus reuteri and unique oligosaccharides and glycoprotein may serve as receptor analogues for pathogenic bacteria, e.g., enterotoxigenic Escherichia coli (ETEC). These receptor analogues block lectin domains of bacterial adhesins and thus prevent adherence of pathogens to the gut wall, thereby avoiding initiation of post-weaning diarrhea. In conclusion, dietary fiber and other carbohydrates may be important solutions to maintain gut health when antibiotics are removed as growth promotants from swine feeds.

Variation of Antigen 43 self-association modulates bacterial compacting within aggregates and biofilms

The formation of aggregates and biofilms enhances bacterial colonisation and infection progression by affording protection from antibiotics and host immune factors. Despite these advantages there is a trade-off, whereby bacterial dissemination is reduced. As such, biofilm development needs to be controlled to suit adaptation to different environments. Here we investigate members from one of largest groups of bacterial adhesins, the autotransporters, for their critical role in the assembly of bacterial aggregates and biofilms. We describe the structural and functional characterisation of autotransporter Ag43 variants from different Escherichia coli pathotypes. We show that specific interactions between amino acids on the contacting interfaces of adjacent Ag43 proteins drives a common mode of trans-association that leads to cell clumping. Furthermore, subtle variation of these interactions alters aggregation kinetics and the degree of compacting within cell clusters. Together, our structure–function investigation reveals an underlying molecular basis for variations in the density of bacterial communities.

Platelets, Bacterial Adhesins and the Pneumococcus.

Systemic infections with pathogenic or facultative pathogenic bacteria are associated with activation and aggregation of platelets leading to thrombocytopenia and activation of the clotting system. Bacterial proteins leading to platelet activation and aggregation have been identified, and while platelet receptors are recognized, induced signal transduction cascades are still often unknown. In addition to proteinaceous adhesins, pathogenic bacteria such as Staphylococcus aureus and Streptococcus pneumoniae also produce toxins such as pneumolysin and alpha-hemolysin. They bind to cellular receptors or form pores, which can result in disturbance of physiological functions of platelets. Here, we discuss the bacteria-platelet interplay in the context of adhesin–receptor interactions and platelet-activating bacterial proteins, with a main emphasis on S. aureus and S. pneumoniae. More importantly, we summarize recent findings of how S. aureus toxins and the pore-forming toxin pneumolysin of S. pneumoniae interfere with platelet function. Finally, the relevance of platelet dysfunction due to killing by toxins and potential treatment interventions protecting platelets against cell death are summarized.

How bacteria utilize sialic acid during interactions with the host: snip, snatch, dispatch, match and attach.

N -glycolylneuraminic acid (Neu5Gc), and its precursor N-acetylneuraminic acid (Neu5Ac), commonly referred to as sialic acids, are two of the most common glycans found in mammals. Humans carry a mutation in the enzyme that converts Neu5Ac into Neu5Gc, and as such, expression of Neu5Ac can be thought of as a ‘human specific’ trait. Bacteria can utilize sialic acids as a carbon and energy source and have evolved multiple ways to take up sialic acids. In order to generate free sialic acid, many bacteria produce sialidases that cleave sialic acid residues from complex glycan structures. In addition, sialidases allow escape from innate immune mechanisms, and can synergize with other virulence factors such as toxins. Human-adapted pathogens have evolved a preference for Neu5Ac, with many bacterial adhesins, and major classes of toxin, specifically recognizing Neu5Ac containing glycans as receptors. The preference of human-adapted pathogens for Neu5Ac also occurs during biosynthesis of surface structures such as lipo-oligosaccharide (LOS), lipo-polysaccharide (LPS) and polysaccharide capsules, subverting the human host immune system by mimicking the host. This review aims to provide an update on the advances made in understanding the role of sialic acid in bacteria-host interactions made in the last 5–10 years, and put these findings into context by highlighting key historical discoveries. We provide a particular focus on ‘molecular mimicry’ and incorporation of sialic acid onto the bacterial outer-surface, and the role of sialic acid as a receptor for bacterial adhesins and toxins.

Structure of the decoy module of human glycoprotein 2 and uromodulin and its interaction with bacterial adhesin FimH

Glycoprotein 2 (GP2) and uromodulin (UMOD) filaments protect against gastrointestinal and urinary tract infections by acting as decoys for bacterial fimbrial lectin FimH. By combining AlphaFold2 predictions with X-ray crystallography and cryo-EM, we show that these proteins contain a bipartite decoy module whose new fold presents the high-mannose glycan recognized by FimH. The structure rationalizes UMOD mutations associated with kidney diseases and visualizes a key epitope implicated in cast nephropathy.

Mouse Gastric Epithelial Cells Resist CagA Delivery by the Helicobacter pylori Type IV Secretion System.

The initial step in bacterial infection is adherence of the bacterium to the target cell surface. Helicobacter pylori exploits the interaction of bacterial adhesin protein HopQ with human epithelial CEACAMs (CEACAM1, 5, and 6) to stably adhere to gastric epithelial cells, which is necessary for delivery of the H. pylori CagA oncoprotein into the epithelial cells via a type IV secretion system. In contrast to human CEACAMs, however, HopQ does not interact with Ceacam1 (mouse CEACAM1) in vitro or in CHO cells ectopically expressing Ceacam1. Since the mouse genome lacks Ceacam5 and Ceacam6, no significant HopQ–Ceacam interaction may occur in mouse gastric epithelial cells. Here, we found that the mouse stomach has a much lower expression level of Ceacam1 than the expression level of CEACAM1 in the human stomach. Consistently, mouse gastric epithelial cells resist CagA delivery by cagA-positive H. pylori, and the delivery is restored by ectopic expression of human CEACAM1 or CEACAM5 in mouse gastric epithelial cells. Thus, despite the fact that mice are routinely used for H. pylori infection studies, a low expression level of Ceacam1 in the mouse stomach together with the loss or greatly reduced interaction of HopQ with Ceacams make the mouse an inappropriate model for studying the role of H. pylori-delivered CagA in gastric pathogenesis, including the development of gastric cancer.

Profilometer Comparison of the Surface Roughness of Four Denture Base Resins: An In Vitro Study

Background: The roughness of denture base materials is mainly affected by inherent material features, the polishing technique, and the operator’s manual skills. The surface irregularities of the denture base resin’s roughness profile is one of the components characterizing the superficial topography of dental prostheses, and it is a critical parameter for describing surface morphology. Generally, the increment of the surface roughness minimizes cleanability and promotes the rate of bacterial adherence, affecting the expression of bacterial adhesins. The purpose of this in vitro study was to investigate the roughness of four commercially available denture base resins employed for removable prosthodontics. Methods: Twenty-five specimens were realized and submitted to observation for three dimensions (vertically, horizontally, 45°). Average surface roughness (Ra), Rv, Rp, and Rq were measured with a calibrated mechanical roughness tester (Taylor Hobson Surtronic 25; Taylor Hobson, Leicester, UK). Data were analyzed through a Kruskal–Wallis test. Results: Significant differences in Ra between the groups were assessed. Baltic Denture System™ (Merz Dental GmbH; Lütjenburg, Germania) showed a lower surface roughness coefficient and a more homogeneous surface. Conclusions: The functional importance of surface roughness parameters for denture base materials must be explored, not only considering recognized surface features.