Heparin-binding motifs and biofilm formation by Candida albicans

MBOVJF4278_00820 encodes a novel cytoadhesin of Mycoplasma bovis binding to heparin

Mycoplasma bovis, a minimal bacterium but a notorious cattle pathogen, leads to serious economic losses. This pathogen binding to host cells is emerging as a complex process involving a broad range of surface-exposed structures. For mycoplasma, adhering to host tissue is the first and crucial step of infection. It is well known that the molecules contributing to microbial cytoadhesion are important virulence factors. Here, we cloned, expressed, and purified the recombinant protein, which is encoded by MBOVJF4278_00820, and induced polyclonal antibodies for it in mice. The cytoadhesive properties of this surface-exposed protein were demonstrated on embryonic bovine lung (EBL) and Madin-Darby bovine kidney (MDBK) cells. Furthermore, heparin as the binding target was confirmed, and the characteristics of the interaction between this protein and heparin have also been analyzed. Our data indicate that the surface-associated MBOVJF4278_00820-encoded protein is a novel adhesion-related factor of Mycoplasma bovis.IMPORTANCEAdhesins are crucial in facilitating Mycoplasma bovis infection. In this study, we identified a specific Mycoplasma bovis adhesin that interacts with heparin on the surface of host cells. Given that heparin is ubiquitously distributed across a wide range of tissue cells, the identification of the heparin-binding adhesin is significant for elucidating how Mycoplasma bovis targets diverse host cells and triggers a spectrum of clinical manifestations.

Sulfated glycosaminoglycans are host epithelial cell targets of the Candida albicans toxin candidalysin

Candidalysin, a cytolytic peptide produced by the fungal pathogen Candida albicans, is a key virulence factor. However, its host cell targets remain elusive. Here we performed a genome-wide loss-of-function CRISPR screen in the TR146 human oral epithelial cell line and identified that disruption of genes (XYLT2, B3GALT6 and B3GAT3) in glycosaminoglycan (GAG) biosynthesis conferred resistance to damage induced by candidalysin and live C. albicans. Surface plasmon resonance and atomic force and electron microscopy indicated that candidalysin binds to sulfated GAGs, facilitating its enrichment on the host cell surface. Adding exogenous sulfated GAGs or the analogue dextran sulfate protected cells against candidalysin-induced damage. Dextran sulfate also inhibited C. albicans invasion and fungal-induced epithelial cell cytokine production. In mice with vulvovaginal candidiasis, topical dextran sulfate administration reduced intravaginal tissue damage and inflammation. Collectively, sulfated GAGs are epithelial cell targets of candidalysin and can be used therapeutically to protect cells from candidalysin-induced damage.

A genome-scale screen identifies sulfated glycosaminoglycans as pivotal in epithelial cell damage by Candida albicans

Candidalysin is a cytolytic peptide produced by the opportunistic fungal pathogen Candida albicans. This peptide is a key virulence factor in mouse models of mucosal and hematogenously disseminated candidiasis. Despite intense interest in the role of candidalysin in C. albicans pathogenicity, its host cell targets have remained elusive. To fill this knowledge gap, we performed a genome-wide loss-of-function CRISPR screen in a human oral epithelial cell line to identify specific host factors required for susceptibility to candidalysin-induced cellular damage. Among the top hits were XYLT2, B3GALT6 and B3GAT3, genes that function in glycosaminoglycan (GAG) biosynthesis. Deletion of these genes led to the absence of GAGs such as heparan sulfate on the epithelial cell surface and increased resistance to damage induced by both candidalysin and live C. albicans. Biophysical analyses including surface plasmon resonance and atomic force and electron microscopy indicated that candidalysin physically binds to sulfated GAGs, facilitating its oligomerization or enrichment on the host cell surface. The addition of exogenous sulfated GAGs or the GAG analogue dextran sulfate protected cells against candidalysin-induced damage. Dextran sulfate, but not non-sulfated dextran, also inhibited epithelial cell endocytosis of C. albicans and fungal-induced epithelial cell cytokine and chemokine production. In a murine model of vulvovaginal candidiasis, topical dextran sulfate administration reduced host tissue damage and decreased intravaginal IL-1β and neutrophil levels. Collectively, these data indicate that GAGs are epithelial cell targets of candidalysin and can be used therapeutically to protect cells from candidalysin-induced damage.

Insights into copper sensing and tolerance in Pneumocystis species

Introduction

Pneumocystis species are pathogenic fungi known to cause pneumonia in immunocompromised mammals. They are obligate to their host, replicate extracellularly in lung alveoli and thrive in the copper-enriched environment of mammalian lungs. In this study, we investigated the proteome of Pneumocystis murina, a model organism that infects mice, in the context of its copper sensing and tolerance.

Methods and results

The query for copper-associated annotations in FungiDB followed by a manual curation identified only 21 genes in P. murina, significantly fewer compared to other clinically relevant fungal pathogens or phylogenetically similar free-living fungi. We then employed instrumental analyses, including Size-Exclusion Chromatography Inductively Coupled Plasma Mass Spectrometry (SEC-ICP-MS), Immobilized Metal Affinity Chromatography (IMAC), and Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS), to isolate and identify copper-binding proteins from freshly extracted organisms, revealing 29 distinct cuproproteins. The RNA sequencing (RNA-seq) analysis of P. murina exposed to various CuSO4 concentrations at three temporal intervals (0.5, 2, and 5 h) indicated that significant gene expression changes occurred only under the highest CuSO4 concentration probed (100 μM) and the longest exposure duration (5 h). This stimulus led to the upregulation of 43 genes and downregulation of 27 genes compared to untreated controls. Quantitative PCR (qPCR) confirmed the expression of four out of eight selected upregulated genes, including three assumed transcription factors (PNEG_01236, PNEG_01675, and PNEG_01730) and a putative copper transporter (PNEG_02609). Notably, the three applied methodologies - homology-based annotation, SEC-ICP-MS/IMAC/LC-MS/MS, and RNA-seq - yielded largely distinct findings, with only four genes (PNEG_02587, PNEG_03319, PNEG_02584, and PNEG_02989) identified by both instrumental methods.

Discussion

The insights contribute to the broader knowledge of Pneumocystis copper homeostasis and provide novel facets of host-pathogen interactions for extracellular pathogens. We suggest that future studies of Pneumocystis pathogenicity and copper stress survival should consider the entire spectrum of identified genes.

Inhibition of bacterial swimming by heparin binding of flagellin FliC from Escherichia coli strain Nissle 1917

Escherichia coli Nissle1917 (EcN) is a non-pathogenic probiotic strain widely used to maintain gut health, treat gastrointestinal disorders, and modulate the gut microbiome due to its anti-inflammatory and competitive exclusion effects against pathogenic bacteria. Heparin, abundant on intestinal mucosal surfaces, is a highly sulfated glycosaminoglycan primarily produced by mast cells. Currently, the interaction between EcN surface protein and heparin has remained elusive. In this study, the flagellin FliC responsible for EcN's movement was separated and characterized as a heparin binding protein by mass spectrometry (MS) analysis. The recombinant FliC protein, expressed by plasmid pET28a( +)-fliC, was further prepared to confirm the interaction between FliC and heparin. The results showed that heparin-Sepharose's ability to bind FliC was 48-fold higher than its ability to bind the negative control, bovine serum albumin (BSA). Neither the knockout of gene fliC nor the addition of heparin affects the growth of EcN, but both significantly inhibit the swimming of EcN. Adding 10 mg/ml heparin reduced the swimming diameter of the wild type and the complemented strain to 29-41% of the original, but that did not affect the swimming ability of the knockout strains. These results demonstrate that heparin interacts with EcN flagellin FliC and inhibits bacteria swimming. Exploring this interaction could improve our understanding of the relationship between hosts and microorganisms and provide a potential basis for disease treatment.

Effect of Glycosaminoglycans on Cryptosporidium Oocyst Attachment and Excystation

Cryptosporidium causes severe gastrointestinal disease resulting from the ingestion of oocysts, followed by oocyst excystation in the small intestine and the release of infective sporozoites. An understudied strategy for Cryptosporidium inactivation is purposeful oocyst excystation, as sporozoites do not survive long in the environment. This study showed that C. parvum oocyst excystation was induced by direct contact with various glycosaminoglycans (GAGs), including heparin (Hep), chondroitin sulfate A (CSA), and hyaluronan (HA), assembled on polydopamine (PD)-functionalized surfaces. PD surfaces elicited 97.9 ± 3.6% oocyst attachment, with some of the attached oocysts partially (7.3 ± 1.3%) or fully (4.0 ± 0.6%) excysted after 4 days. The PD-GAG surfaces (GAG concentration = 2 mg/mL) elicited similarly high attachment (>97%) and higher oocyst excystation efficiencies after 4 days. The PD-Hep surfaces elicited the highest number of attached excysted oocysts (11.8 ± 0.63% partially excysted; 11.9 ± 0.49% fully excysted), and the PD-HA surfaces elicited the lowest (8.8 ± 2.1% partially excysted; 7.8 ± 1.2% fully excysted). Surface characterization revealed that the addition of GAGs to the PD surface changed both the surface roughness as well as the surface wettability. Treatment of oocysts with an enzyme that degraded the surface glycocalyx markedly reduced excystation (to <2%) of the oocysts attached to the PD and PD-GAG surfaces. These findings suggest that GAGs provide an important local signal for the excystation of C. parvum oocysts and that certain surface-expressed oocyst receptors are necessary for efficient excystation. These oocyst-receptor relationships may be useful in the design of functionalized surfaces for the purposeful inactivation of oocysts in the environment or in water treatment systems. IMPORTANCE Polydopamine surfaces functionalized with glycosaminoglycans were shown to facilitate the attachment and excystation of Cryptosporidium parvum oocysts. Our findings suggest that a surface-expressed receptor on the oocyst wall plays a key role in excystation, with glycosaminoglycans serving as ligands that trigger the initiation of the process. Future technologies and treatment strategies designed to promote premature excystation of oocysts will minimize the ingestion of sporozoites that initiate infection. Therefore, the results from this study have important implications for the protection of public health from waterborne cryptosporidiosis and may serve as a foundation for engineered surfaces designed to remove oocysts from surface waters or inactivate oocysts in water treatment systems.

Mycoplasma Bovis adhesins and their target proteins

Bovine mycoplasmosis is an important infectious disease of cattle caused by Mycoplasma bovis (M. bovis) which poses a serious threat to the breeding industry. Adhesin is involved in the initial process of M. bovis colonization, which is closely related to the infection, cell invasion, immune escape and virulence of this pathogenic microorganism. For the reason that M. bovis lacks a cell wall, its adhesin is predominantly located on the surface of the cell membrane. The adhesins of M. bovis are usually identified by adhesion and adhesion inhibition analysis, and more than 10 adhesins have been identified so far. These adhesins primarily bind to plasminogen, fibronectin, heparin and amyloid precursor-like protein-2 of host cells. This review aims to concisely summarize the current knowledge regarding the adhesins of M. bovis and their target proteins of the host cell. Additionally, the biological characteristics of the adhesin will be briefly analyzed.

Antifungal lock therapy: an eternal promise or an effective alternative therapeutic approach?

Each year, millions of central venous catheter insertions are performed in intensive care units worldwide. The usage of these indwelling devices is associated with a high risk of bacterial and fungal colonization, leading to the development of microbial consortia, namely biofilms. These sessile structures provide fungal cells with resistance to the majority of antifungals, environmental stress and host immune responses. Based on different guidelines, colonized/infected catheters should be removed and changed immediately in the case of Candida‐related central line infections. However, catheter replacement is not feasible for all patient populations. An alternative therapeutic approach may be antifungal lock therapy, which has received high interest, especially in the last decade. This review summarizes the published Candida‐related in vitro, in vivo data and case studies in terms of antifungal lock therapy. The number of clinical studies remains limited and further studies are needed for safe implementation of the antifungal lock therapy into clinical practice.

Glycosaminoglycan-Protein Interactions and Their Roles in Human Disease

Glycosaminoglycans (GAGs) are a family of linear and negatively charged polysaccharides that exist ubiquitously on the human cell surface as well as in the extracellular matrix. GAGs interact with a wide range of proteins, including proteases, growth factors, cytokines, chemokines and adhesion molecules, enabling them to mediate many physiological processes, such as protein function, cellular adhesion and signaling. GAG-protein interactions participate in and intervene in a variety of human diseases, including cardiovascular disease, infectious disease, neurodegenerative diseases and tumors. The breakthrough in analytical tools and approaches during the last two decades has facilitated a greater understanding of the importance of GAG-protein interactions and their roles in human diseases. This review focuses on aspects of the molecular basis and mechanisms of GAG-protein interactions involved in human disease. The most recent advances in analytical tools, especially mass spectrometry-based GAG sequencing and binding motif characterization methods, are introduced. An update of selected families of GAG binding proteins is presented. Perspectives on development of novel therapeutics targeting specific GAG-protein interactions are also covered in this review.

Flexible Synthetic Carbohydrate Receptors as Inhibitors of Viral Attachment

Carbohydrate-receptor interactions are often involved in the docking of viruses to host cells, and this docking is a necessary step in the virus life cycle that precedes infection and, ultimately, replication. Despite the conserved structures of the glycans involved in docking, they are still considered "undruggable", meaning these glycans are beyond the scope of conventional pharmacological strategies. Recent advances in the development of synthetic carbohydrate receptors (SCRs), small molecules that bind carbohydrates, could bring carbohydrate-receptor interactions within the purview of druggable targets. Here we discuss the role of carbohydrate-receptor interactions in viral infection, the evolution of SCRs, and recent results demonstrating their ability to prevent viral infections in vitro. Common SCR design strategies based on boronic ester formation, metal chelation, and noncovalent interactions are discussed. The benefits of incorporating the idiosyncrasies of natural glycan-binding proteins-including flexibility, cooperativity, and multivalency-into SCR design to achieve nonglucosidic specificity are shown. These studies into SCR design and binding could lead to new strategies for mitigating the grave threat to human health posed by enveloped viruses, which are heavily glycosylated viroids that are the cause of some of the most pressing and untreatable diseases, including HIV, Dengue, Zika, influenza, and SARS-CoV-2.

Antifungal and Cytotoxic Evaluation of Photochemically Synthesized Heparin-Coated Gold and Silver Nanoparticles

Heparin-based silver nanoparticles (AgHep-NPs) and gold nanoparticles (AuHep-NPs) were produced by a photochemical method using silver nitrate and chloroauric acid as metal precursors and UV light at 254 nm. UV-Vis spectroscopy graphs showed absorption for AgHep-NPs and AuHep-NPs at 420 nm and 530 nm, respectively. TEM revealed a pseudospherical morphology and a small size, corresponding to 10-25 nm for AgHep-NPs and 1.5-7.5 nm for AuHep-NPs. Their antifungal activity against Candida albicans, Issatchenkia orientalis (Candida krusei), and Candida parapsilosis was assessed by the microdilution method. We show that AgHep-NPs were effective in decreasing fungus density, whereas AuHep-NPs were not. Additionally, the viability of human gingival fibroblasts was preserved by both nanoparticle types at a level above 80%, indicating a slight cytotoxicity. These results are potentially useful for applications of the described NPs mainly in dentistry and, to a lesser extent, in other biomedical areas.

Mimicking the Endothelium: Dual Action Heparinized Nitric Oxide Releasing Surface

The management of thrombosis and bacterial infection is critical to ensure the functionality of medical devices. While administration of anticoagulants is the current antithrombotic clinical practice, a variety of complications, such as uncontrolled hemorrhages or heparin-induced thrombocytopenia, can occur. Additionally, infection rates remain a costly and deadly complication associated with use of these medical devices. It has been hypothesized that if a synthetic surface could mimic the biochemical mechanisms of the endothelium of blood vessels, thrombosis could be reduced, anticoagulant use could be avoided, and infection could be prevented. Herein, the interfacial biochemical effects of the endothelium were mimicked by altering the surface of medical grade silicone rubber (SR). Surface modification was accomplished via heparin surface immobilization (Hep) and the inclusion of a nitric oxide (NO) donor into the SR polymeric matrix to achieve synergistic effects (Hep-NO-SR). An in vitro bacteria adhesion study revealed that Hep-NO-SR exhibited a 99.46 ± 0.17% reduction in viable bacteria adhesion compared to SR. An in vitro platelet study revealed Hep-NO-SR reduced platelet adhesion by 84.12 ± 6.19% compared to SR, while not generating a cytotoxic response against fibroblast cells. In a 4 h extracorporeal circuit model without systemic anticoagulation, all Hep-NO-SR samples were able to maintain baseline platelet count and device patency; whereas 66% of SR samples clotted within the first 2 h of study. Results indicate that Hep-NO-SR creates a more hemocompatible and antibacterial surface by mimicking two key biochemical functions of the native endothelium.

The Diverse Functional Roles of Elongation Factor Tu (EF-Tu) in Microbial Pathogenesis

Elongation factor thermal unstable Tu (EF-Tu) is a G protein that catalyzes the binding of aminoacyl-tRNA to the A-site of the ribosome inside living cells. Structural and biochemical studies have described the complex interactions needed to effect canonical function. However, EF-Tu has evolved the capacity to execute diverse functions on the extracellular surface of both eukaryote and prokaryote cells. EF-Tu can traffic to, and is retained on, cell surfaces where can interact with membrane receptors and with extracellular matrix on the surface of plant and animal cells. Our structural studies indicate that short linear motifs (SLiMs) in surface exposed, non-conserved regions of the molecule may play a key role in the moonlighting functions ascribed to this ancient, highly abundant protein. Here we explore the diverse moonlighting functions relating to pathogenesis of EF-Tu in bacteria and examine putative SLiMs on surface-exposed regions of the molecule.

Advances in the prevention and management of central-line-associated bloodstream infections: The role of chelator-based catheter locks

The proper functioning of central lines is imperative for the management of patients with cancer or on hemodialysis. However, these lifelines can become infected and can malfunction.Chelators such as citrate and EDTA have been widely studied alone or in combination with other antimicrobial agents in catheter lock solutions to prevent catheter-related bloodstream infections and to maintain catheter patency. Given their anticoagulation, antiplatelet aggregation, antibiofilm, antimicrobial activity, safety profile, as well as their low cost, chelators have long been considered alternatives to heparin and a vital component of catheter lock solutions. In this review, we present a detailed summary of the properties of chelators and in vitro and in vivo studies of chelator-containing lock solutions.

Epidemiology of Infectious and Noninfectious Catheter Complications in Patients Receiving Home Parenteral Nutrition: A Systematic Review and Meta-Analysis

Patients receiving parenteral nutrition (PN) as their primary source of nutrition are at high risk for both infectious and noninfectious catheter complications (catheter-related infections, catheter occlusion, and venous thrombosis). The aim of this review was to synthesize and evaluate what is known about catheter complications and prevention strategies in the PN population. Three electronic databases (Medline, Embase, and CINAHL) were screened for studies published between January 2012 and February 2019 regarding infectious and noninfectious catheter complications in patients receiving PN. Rates of infectious and noninfectious catheter complications, prevalence of causative pathogens, potential risk factors, and prevention strategies via the use of antimicrobial lock therapy (ALT) were assessed. Fifty-three catheter complication studies and 12 ALT studies were included. Studies were grouped by definition of complication: catheter-related bloodstream infections (CRBSI) or central line-associated bloodstream infections (CLABSI). Random effects summary rates per 1000 catheter days were 0.85 CRBSI episodes (95% CI 0.27-2.64) and 1.65 CLABSI episodes (95% CI 1.09-2.48). Use of taurolidine or ethanol ALT was efficacious in reducing infectious catheter complications; however, several studies had concerns for adverse mechanical complications. Potential risk factors for catheter complications were highly varied and often contradictory between studies. The rates of catheter complications were higher among catheterized patients receiving PN compared with nationally reported rates of complications in all catheterized patients. Risk factors for catheter complications need to be better understood for targeted prophylactic use of ALT. Future studies are warranted; however, they should be conducted using more standardized definitions and criteria.

Therapeutic strategies to target microbial protein-glycosaminoglycan interactions

Glycans are involved in a plethora of human pathologies including infectious diseases. Especially, glycosaminoglycans (GAGs), like heparan sulfate and chondroitin sulfate, have been found to be involved in different crucial stages of microbial invasion. Here, we review various therapeutic approaches, which target the interface of host GAGs and microbial proteins and discuss their limitations and challenges for drug development.

[Identification of Heparin-binding Proteins on the Cell Surface of Cryptococcus neoformans]

Interactions between virulence factors of pathogens and host responses play an important role in the establishment of infection by microbes. We focused on interactions between Cryptococcus neoformans proteins and heparin, which is abundant on host epithelial cells. Surface proteins were extracted and analyzed. Fractions from anion-exchange column chromatography interacted with heparin in surface plasmon resonance analyses. Heparin-binding proteins were purified and then separated by gel electrophoresis; and were identified as transaldolase, glutathione-disulfide reductase, and glyoxal oxidase. These results imply that multifunctional molecules on C. neoformans cells, such as those involved in heparin binding, may play roles in adhesion that trigger responses in the host.

Heparin: role in protein purification and substitution with animal-component free material

Heparin is a highly sulfated polysaccharide which belongs to the family of glycosaminoglycans. It is involved in various important biological activities. The major biological purpose is the inhibition of the coagulation cascade to maintain the blood flow in the vasculature. These properties are employed in several therapeutic drugs. Heparin’s activities are associated with its interaction to various proteins. To date, the structural heparin-protein interactions are not completely understood. This review gives a general overview of specific patterns and functional groups which are involved in the heparin-protein binding. An understanding of the heparin-protein interactions at the molecular level is not only advantageous in the therapeutic application but also in biotechnological application of heparin for downstreaming. This review focuses on the heparin affinity chromatography. Diverse recombinant proteins can be successfully purified by this method. While effective, it is disadvantageous that heparin is an animal-derived material. Animal-based components carry the risk of contamination. Therefore, they are liable to strict quality controls and the validation of effective good manufacturing practice (GMP) implementation. Hence, adequate alternatives to animal-derived components are needed. This review examines strategies to avoid these disadvantages. Thereby, alternatives for the provision of heparin such as chemical synthesized heparin, chemoenzymatic heparin, and bioengineered heparin are discussed. Moreover, the usage of other chromatographic systems mimetic the heparin effect is reviewed.

Heparin Mimics Extracellular DNA in Binding to Cell Surface-Localized Proteins and Promoting Staphylococcus aureus Biofilm Formation

Staphylococcus aureus and coagulase-negative staphylococci (CoNS) are the leading causes of catheter implant infections. Identifying the factors that stimulate catheter infection and the mechanism involved is important for preventing such infections. Heparin, the main component of catheter lock solutions, has been shown previously to stimulate S. aureus biofilm formation through an unknown pathway. This work identifies multiple heparin-binding proteins in S. aureus, and it reveals a potential mechanism through which heparin enhances biofilm capacity. Understanding the details of the heparin enhancement effect could guide future use of appropriate lock solutions for catheter implants.

Staphylococcus aureus is a leading cause of catheter-related bloodstream infections. Biofilms form on these implants and are held together by a matrix composed of proteins, polysaccharides, and extracellular DNA (eDNA). Heparin is a sulfated glycosaminoglycan that is routinely used in central venous catheters to prevent thrombosis, but it has been shown to stimulate S. aureus biofilm formation through an unknown mechanism. Data presented here reveal that heparin enhances biofilm capacity in many S. aureus and coagulase-negative staphylococcal strains, and it is incorporated into the USA300 methicillin-resistant S. aureus (MRSA) biofilm matrix. The S. aureus USA300 biofilms containing heparin are sensitive to proteinase K treatment, which suggests that proteins have an important structural role during heparin incorporation. Multiple heparin-binding proteins were identified by proteomics of the secreted and cell wall fractions. Proteins known to contribute to biofilm were identified, and some proteins were reported to have the ability to bind eDNA, such as the major autolysin (Atl) and the immunodominant surface protein B (IsaB). Mutants defective in IsaB showed a moderate decrease in biofilm capacity in the presence of heparin. Our findings suggested that heparin is substituting for eDNA during S. aureus biofilm development. To test this model, eDNA content was increased in biofilms through inactivation of nuclease activity, and the heparin enhancement effect was attenuated. Collectively, these data support the hypothesis that S. aureus can incorporate heparin into the matrix and enhance biofilm capacity by taking advantage of existing eDNA-binding proteins.

IMPORTANCEStaphylococcus aureus and coagulase-negative staphylococci (CoNS) are the leading causes of catheter implant infections. Identifying the factors that stimulate catheter infection and the mechanism involved is important for preventing such infections. Heparin, the main component of catheter lock solutions, has been shown previously to stimulate S. aureus biofilm formation through an unknown pathway. This work identifies multiple heparin-binding proteins in S. aureus, and it reveals a potential mechanism through which heparin enhances biofilm capacity. Understanding the details of the heparin enhancement effect could guide future use of appropriate lock solutions for catheter implants.

A Risk Score for Fluconazole Failure among Patients with Candidemia

This study aimed to develop a prediction model to identify patients with candidemia who were at high risk of failing fluconazole treatment. Adult patients in the United States with candidemia who received fluconazole during hospitalization were selected from the Cerner Health Facts Hospital Database (04/2004 to 03/2013). Fluconazole failure was defined as switching/adding another antifungal, positive Candida culture ≥10 days after fluconazole initiation, or death during hospitalization. Patients were randomized into modeling and validation samples. Using the modeling sample, a regression analysis of least absolute shrinkage and selection operator was used to select risk predictors of fluconazole failure (demographics, Candida species, initiation of fluconazole before positive culture and after admission, and comorbidities, procedures, and treatments during the 6 months before admission and fluconazole initiation). The prediction model was evaluated using the validation sample. We found that of 987 identified patients (average age of 61 years, 51% male, 72% Caucasian), 49% failed and 51% did not fail fluconazole treatment. Of those who failed, 70% switched or added another antifungal, 21% had a second positive Candida test, and 42% died during hospitalization. Nine risk factors were included in the prediction model: days to start fluconazole after admission, Candida glabrata or Candida krusei infection, hematological malignancy, venous thromboembolism (VTE), enteral nutrition, use of nonoperative intubation/irrigation, and other antifungal use. All but VTE were associated with a higher risk of failure. The model's c-statistic was 0.65, with a Hosmer-Lemeshow test P value of 0.23. In summary, this prediction model identified patients with a high risk of fluconazole failure, illustrating the potential value and feasibility of personalizing candidemia treatment.

Drug eluting antimicrobial vascular catheters: Progress and promise

Vascular catheters are critical tools in modern healthcare yet present substantial risks of serious bloodstream infections that exact significant health and economic burdens. Drug-eluting antimicrobial vascular catheters have become important tools in preventing catheter-related bloodstream infections and their importance is expected to increase as significant initiatives are expanded to eliminate and make the occurrence of these infections unacceptable. Here we review clinically significant and emerging drug-eluting antimicrobial catheters within the categories of antibiotic, antiseptic, novel bioactive agents and energy-enhanced drug eluting antimicrobial catheters. Important representatives of each category are reviewed from the standpoints of mechanisms of action, physical-chemical properties, safety, in vitro and clinical effectiveness.

Comparative Efficacies of Antimicrobial Catheter Lock Solutions for Fungal Biofilm Eradication in an in Vitro Model of Catheter-Related Fungemia

Fungal catheter-related bloodstream infections (CRBSIs)-primarily due to Candida species-account for over 12% of all CRBSIs, and have been progressively increasing in prevalence. They present significant health and economic burdens, and high mortality rates. Antimicrobial catheter lock solutions are an important prophylactic option for preventing fungal CRBSIs. In this study, we compared the effectiveness of two FDA-approved catheter lock solutions (heparin and saline) and three experimental antimicrobial catheter lock solutions-30% citrate, taurolidine-citrate-heparin (TCH), and nitroglycerin-citrate-ethanol (NiCE)-in an in vitro model of catheters colonized by fungi. The fungi tested were five different strains of Candida clinical isolates from cancer patients who contracted CRBSIs. Time-to-biofilm-eradication was assessed in the model with 15, 30, and 60 min exposures to the lock solutions. Only the NiCE lock solution was able to fully eradicate all fungal biofilms within 60 min. Neither 30% citrate nor TCH was able to fully eradicate any of the Candida biofilms in this time frame. The NiCE lock solution was significantly superior to TCH in eradicating biofilms of five different Candida species (p = 0.002 for all).

Plasticity of Candida albicans Biofilms

Candida albicans, the most pervasive fungal pathogen that colonizes humans, forms biofilms that are architecturally complex. They consist of a basal yeast cell polylayer and an upper region of hyphae encapsulated in extracellular matrix. However, biofilms formed in vitro vary as a result of the different conditions employed in models, the methods used to assess biofilm formation, strain differences, and, in a most dramatic fashion, the configuration of the mating type locus (MTL). Therefore, integrating data from different studies can lead to problems of interpretation if such variability is not taken into account. Here we review the conditions and factors that cause biofilm variation, with the goal of engendering awareness that more attention must be paid to the strains employed, the methods used to assess biofilm development, every aspect of the model employed, and the configuration of the MTL locus. We end by posing a set of questions that may be asked in comparing the results of different studies and developing protocols for new ones. This review should engender the notion that not all biofilms are created equal.

In Vitro Assessment of the Antimicrobial Efficacy of Optimized Nitroglycerin-Citrate-Ethanol as a Nonantibiotic, Antimicrobial Catheter Lock Solution for Prevention of Central Line-Associated Bloodstream Infections

The rapid, broad-spectrum, biofilm-eradicating activity of the combination of 0.01% nitroglycerin, 7% citrate, and 20% ethanol and its potential as a nonantibiotic, antimicrobial catheter lock solution (ACLS) were previously reported. Here, a nitroglycerin-citrate-ethanol (NiCE) ACLS optimized for clinical assessment was developed by reducing the nitroglycerin and citrate concentrations and increasing the ethanol concentration. Biofilm-eradicating activity was sustained when the ethanol concentration was increased from 20 to 22% which fully compensated for reducing the citrate concentration from 7% to 4% as well as the nitroglycerin concentration from 0.01% to 0.0015% or 0.003%. The optimized formulations demonstrated complete and rapid (2 h) eradication of methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-intermediate Staphylococcus aureus (VISA), methicillin-resistant Staphylococcus epidermidis (MRSE), vancomycin-resistant enterococci (VRE), multidrug-resistant (MDR) Pseudomonas aeruginosa, MDR Klebsiella pneumoniae, MDR Enterobacter cloacae, MDR Acinetobacter baumannii, MDR Escherichia coli, MDR Stenotrophomonas maltophilia, Candida albicans, and Candida glabrata biofilms. The optimized NiCE lock solutions demonstrated anticoagulant activities comparable to those of heparin lock solutions. NiCE lock solution was significantly more effective than taurolidine-citrate-heparin lock solution in eradicating biofilms of Staphylococcus aureus and Candida glabrata The optimized, nonantibiotic, heparin-free NiCE lock solution demonstrates rapid broad-spectrum biofilm eradication as well as effective anticoagulant activity, making NiCE a high-quality ACLS candidate for clinical assessment.

A clamp-like orientation of basic residues set in a parallelogram is essential for heparin binding

While the majority of studies have focused on the biological roles of heparin-binding proteins, relatively little is known about their key residues and structural elements responsible for heparin interaction. In this study, we employed the IgG-binding domain B1 of Streptococcal protein G as a miniature scaffold to investigate how certain positively charged residues within the β-sheet conformation become favorable for heparin binding. By performing a series of arginine substitution mutations followed by gain-of-heparin-binding analysis, we deduced that a clamp-like orientation with discontinuous basic residues separated by ~ 5 Å with ~ 100° interior angle is advantageous for high heparin affinity.

Determination of Biofilm Initiation on Virus-infected Cells by Bacteria and Fungi

The study of polymicrobial interactions across the taxonomic kingdoms that include fungi, bacteria and virus have not been previously examined with respect to how viral members of the microbiome affect subsequent microbe interactions with these virus-infected host cells. The co-habitation of virus with bacteria and fungi is principally present on the mucosal surfaces of the oral cavity and genital tract. Mucosal cells, particularly those with persistent chronic or persistent latent viral infections, could have a significant impact on members of the microbiome through virus alteration in number and type of receptors expressed. Modification in host cell membrane architecture would result in altered ability of subsequent members of the normal flora and opportunistic pathogens to initiate the first step in biofilm formation, i.e., adherence. This study describes a method for quantitation and visual examination of HSV's effect on the initiation of biofilm formation (adherence) of S. aureus and C. albicans.

Glycosaminoglycans and infection

Glycosaminoglycans (GAGs) are complex linear polysaccharides expressed in intracellular compartments, at the cell surface, and in the extracellular environment where they interact with various molecules to regulate many cellular processes implicated in health and disease. Subversion of GAGs is a pathogenic strategy shared by a wide variety of microbial pathogens, including viruses, bacteria, parasites, and fungi. Pathogens use GAGs at virtually every major portals of entry to promote their attachment and invasion of host cells, movement from one cell to another, and to protect themselves from immune attack. Pathogens co-opt fundamental activities of GAGs to accomplish these tasks. This ingenious strategy to subvert essential activities of GAGs likely prevented host organisms from deleting or inactivating these mechanisms during their evolution. The goal of this review is to provide a mechanistic overview of our current understanding of how microbes subvert GAGs at major steps of pathogenesis, using select GAG-pathogen interactions as representative examples.

Candida albicans Shaving to Profile Human Serum Proteins on Hyphal Surface

Candida albicans is a human opportunistic fungus and it is responsible for a wide variety of infections, either superficial or systemic. C. albicans is a polymorphic fungus and its ability to switch between yeast and hyphae is essential for its virulence. Once C. albicans obtains access to the human body, the host serum constitutes a complex environment of interaction with C. albicans cell surface in bloodstream. To draw a comprehensive picture of this relevant step in host-pathogen interaction during invasive candidiasis, we have optimized a gel-free shaving proteomic strategy to identify both, human serum proteins coating C. albicans cells and fungi surface proteins simultaneously. This approach was carried out with normal serum (NS) and heat inactivated serum (HIS). We identified 214 human and 372 C. albicans unique proteins. Proteins identified in C. albicans included 147 which were described as located at the cell surface and 52 that were described as immunogenic. Interestingly, among these C. albicans proteins, we identified 23 GPI-anchored proteins, Gpd2 and Pra1, which are involved in complement system evasion and 7 other proteins that are able to attach plasminogen to C. albicans surface (Adh1, Eno1, Fba1, Pgk1, Tdh3, Tef1, and Tsa1). Furthermore, 12 proteins identified at the C. albicans hyphae surface induced with 10% human serum were not detected in other hypha-induced conditions. The most abundant human proteins identified are involved in complement and coagulation pathways. Remarkably, with this strategy, all main proteins belonging to complement cascades were identified on the C. albicans surface. Moreover, we identified immunoglobulins, cytoskeletal proteins, metabolic proteins such as apolipoproteins and others. Additionally, we identified more inhibitors of complement and coagulation pathways, some of them serpin proteins (serine protease inhibitors), in HIS vs. NS. On the other hand, we detected a higher amount of C3 at the C. albicans surface in NS than in HIS, as validated by immunofluorescence.

Low anticoagulant heparin blocks thrombin-induced endothelial permeability in a PAR-dependent manner

Acute lung injury and acute respiratory distress syndrome are accompanied by thrombin activation and fibrin deposition that enhance lung inflammation, activate endothelial cells and disrupt lung paracellular permeability. Heparin possesses anti-inflammatory properties but its clinical use is limited by hemorrhage and heparin induced thrombocytopenia. We studied the effects of heparin and low anticoagulant 2-O, 3-O desulfated heparin (ODSH) on thrombin-induced increases in paracellular permeability of cultured human pulmonary endothelial cells (ECs). Pretreatment with heparin or ODSH blocked thrombin-induced decrease in the EC transendothelial electrical resistance (TER), attenuated thrombin-stimulated paracellular gap formation and actin cytoskeletal rearrangement. Our data demonstrated that heparin and ODSH had inhibitory effects on thrombin-induced RhoA activation and intracellular calcium elevation. Thrombin-stimulated phosphorylation of the cytoskeletal regulatory proteins, myosin light chain and ezrin/radixin/moesin was also reduced. In these effects, low anticoagulant ODSH was more potent than heparin. Heparin or ODSH alone produced decreases in the EC TER that were abolished by siRNA-mediated depletion of the thrombin receptor, PAR-1. We also demonstrated that, in contrast to heparin, ODSH did not possess thrombin-binding activity. Results suggest that heparin and low anticoagulant ODSH can interfere with thrombin-activated signaling.