Treatment and prevention of urinary tract infection with orally active FimH inhibitors

Novel Nano Drug-Loaded Hydrogel Coatings for the Prevention and Treatment of CAUTI

Catheter-associated urinary tract infection (CAUTI) is a prevalent type of hospital-acquired infection, affecting approximately 15% to 25% of patients with urinary catheters. Long-term use of the catheter can lead to colonization of microorganisms and biofilm formation, and may develop into bacterial CAUTI. However, the frequent replacement of catheters in clinical settings can result in tissue damage, inflammation, ulceration, and additional complications, causing discomfort and pain for patients. In light of these challenges, a novel nanodrug-supported hydrogel coating called NP-AM/FK@OMV-P/H has been developed in this study. Through in vitro experiments, it is confirmed that OMV nano-loaded liquid gel coating has an effective reaction against E.coli HAase and releases antibacterial drugs. This coating has also demonstrated strong inhibition of E.coli and has shown the ability to inhibit the formation of bacterial biofilm. These findings highlight the potential of the OMV nanoparticle gel coating in preventing and treating bacterial infections. Notably, NP-AM/FK@OMV-P/H has exhibited greater efficacy against multidrug-resistant E.coli associated with UTIs compared to coatings containing single antimicrobial peptides or antibiotics. Additionally, it has demonstrated good biosecurity. In conclusion, the NP-AM/FK@OMV-P/H coating holds great potential in providing benefits to patients with CAUTI.

Interface properties of nanostructured carbon-coated biological implants: an overview

The interfaces between medical implants and living tissues are of great complexity because of the simultaneous occurrence of a wide variety of phenomena. The engineering of implant surfaces represents a crucial challenge in material science, but the further improvement of implant properties remains a critical task. It can be achieved through several processes. Among them, the production of specialized coatings based on carbon-based materials stands very promising. The use of carbon coatings allows one to simultaneously fine-tune tribological, mechanical, and chemical properties. Here, we review applications of nanostructured carbon coatings (nanodiamonds, carbon nanotubes, and graphene-related materials) for the improvement of the overall properties of medical implants. We are focusing on biological interactions, improved corrosion resistance, and overall mechanical properties, trying to provide a complete overview within the field.

Mannose-Presenting "Glyco-Colicins" Convert the Bacterial Cell Surface into a Multivalent Adsorption Site for Adherent Bacteria

Biofilm formation is integral to the pathogenesis of numerous adherent bacteria and contributes to antimicrobial resistance (AMR). The rising threat of AMR means the need to develop novel nonbactericidal antiadhesion approaches against such bacteria is more urgent than ever. Both adherent-invasive Escherichia coli (AIEC, implicated in inflammatory bowel disease) and uropathogenic E. coli (UPEC, responsible for ∼80% of urinary tract infections) adhere to terminal mannose sugars on epithelial glycoproteins through the FimH adhesin on their type 1 pilus. Although mannose-based inhibitors have previously been explored to inhibit binding of adherent bacteria to epithelial cells, this approach has been limited by monovalent carbohydrate-protein interactions. Herein, we pioneer a novel approach to this problem through the preparation of colicin E9 bioconjugates that bind to the abundant BtuB receptor in the outer membrane of bacteria, which enables multivalent presentation of functional motifs on the cell surface. We show these bioconjugates label the surface of live E. coli and furthermore demonstrate that mannose-presenting "glyco-colicins" induce E. coli aggregation, thereby using the bacteria, itself, as a multivalent platform for mannose display, which triggers binding to adjacent FimH-presenting bacteria.

ESKAPE pathogens: antimicrobial resistance, epidemiology, clinical impact and therapeutics

The rise of antibiotic resistance and a dwindling antimicrobial pipeline have been recognized as emerging threats to public health. The ESKAPE pathogens - Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa and Enterobacter spp. - were initially identified as critical multidrug-resistant bacteria for which effective therapies were rapidly needed. Now, entering the third decade of the twenty-first century, and despite the introduction of several new antibiotics and antibiotic adjuvants, such as novel β-lactamase inhibitors, these organisms continue to represent major therapeutic challenges. These bacteria share several key biological features, including adaptations for survival in the modern health-care setting, diverse methods for acquiring resistance determinants and the dissemination of successful high-risk clones around the world. With the advent of next-generation sequencing, novel tools to track and combat the spread of these organisms have rapidly evolved, as well as renewed interest in non-traditional antibiotic approaches. In this Review, we explore the current epidemiology and clinical impact of this important group of bacterial pathogens and discuss relevant mechanisms of resistance to recently introduced antibiotics that affect their use in clinical settings. Furthermore, we discuss emerging therapeutic strategies needed for effective patient care in the era of widespread antimicrobial resistance.

Current and emerging strategies to curb antibiotic-resistant urinary tract infections

Rising rates of antibiotic resistance in uropathogenic bacteria compromise patient outcomes and prolong hospital stays. Consequently, new strategies are needed to prevent and control the spread of antibiotic resistance in uropathogenic bacteria. Over the past two decades, sizeable clinical efforts and research advances have changed urinary tract infection (UTI) treatment and prevention strategies to conserve antibiotic use. The emergence of antimicrobial stewardship, policies from national societies, and the development of new antimicrobials have shaped modern UTI practices. Future UTI management practices could be driven by the evolution of antimicrobial stewardship, improved and readily available diagnostics, and an improved understanding of how the microbiome affects UTI. Forthcoming UTI treatment and prevention strategies could employ novel bactericidal compounds, combinations of new and classic antimicrobials that enhance bacterial killing, medications that prevent bacterial attachment to uroepithelial cells, repurposing drugs, and vaccines to curtail the rising rates of antibiotic resistance in uropathogenic bacteria and improve outcomes in people with UTI.

Bioinspired Nanozymes as Nanodecoys for Urinary Tract Infection Treatment

Urinary tract infections (UTIs), common bacterial infections in communities and medical facilities, are mainly mediated by FimH. The glycan sites of the uromodulin protein play a crucial role in protecting against UTIs by interacting with FimH. A bioinspired approach using glycan-FimH interactions may effectively reduce bacteria through an antiadhesive mechanism, thereby curbing bacterial resistance. However, typical antiadhesive therapy alone fails to address the excessive reactive oxygen species and inflammatory response during UTIs. To bridge this gap, antioxidant nanozymes with antiadhesive ability were developed as nanodecoys to counter bacteria and inflammation. Specifically, ultrasmall dextran-coated ceria (DEC) was engineered to address UTIs, with dextran blocking FimH adhesion and ceria exhibiting anti-inflammatory properties. DECs, metabolizable by the kidneys, reduced bacterial content in the urinary tract, mitigating inflammation and tissue damage. In murine models, DECs successfully treated acute UTIs, repeated infections, and catheter-related UTIs. This dual approach not only highlights the potential of nanozymes for UTIs but also suggests applicability to other FimH-induced infections in the lungs and bowels, marking a significant advancement in nanozyme-based clinical approaches.

Discovery of Orally Bioavailable FmlH Lectin Antagonists as Treatment for Urinary Tract Infections

FmlH, a bacterial adhesin of uropathogenic Escherichia coli (UPEC), has been shown to provide a fitness advantage in colonizing the bladder during chronic urinary tract infections (UTIs). Previously reported ortho-biphenyl glycosides based on βGal and βGalNAc have excellent binding affinity to FmlH and potently block binding to its natural carbohydrate receptor, but they lack oral bioavailability. In this paper, we outline studies where we have optimized compounds for improved pharmacokinetics, leading to the discovery of novel analogues with good oral bioavailability. We synthesized galactosides with the anomeric O-linker replaced with more stable S- and C-linked linkers. We also investigated modifications to the GalNAc sugar and modifications to the biphenyl aglycone. We identified GalNAc 69 with an IC50 of 0.19 μM against FmlH and 53% oral bioavailability in mice. We also obtained a FimlH-bound X-ray structure of lead compound 69 (AM4085) which has potential as a new antivirulence therapeutic for UTIs.

Nature of the Interaction of Alpha-D-Mannose and Escherichia coli Bacteria, and Implications for its Regulatory Classification. A Delphi Panel European Consensus Based on Chemistry and Legal Evidence

The nature of alpha-D-mannose-natural aldohexose sugar, C-2 glucose epimer, whose intended use is for preventing urinary tract infections-in the interaction with E. coli is addressed in order to drive the issue of its regulatory classification as a medicinal product or medical device. PRISMA systematic review approach was applied; Delphi Panel method was used to target consensus on statements retrieved from evidence. Based on regulatory definitions and research evidence, the mechanism of D-mannose does not involve a metabolic or immunological action while there is uncertainty regarding the pharmacological action. Specific interaction between the product and the bacteria within the body occurs, but its nature is inert: it does not induce a direct response activating or inhibiting body processes. Moreover, the action of D-mannose takes place, even if inside the bladder, outside the epithelium on bacteria that have not yet invaded the urothelial tissue. Therefore, its mechanism of action is not directed to host structures but to structures (bacteria) external to the host's tissues. On the basis of current regulation, the uncertainty as regard a pharmacological action of alpha-D-mannose makes possible its medical device classification: new regulations and legal judgments can add further considerations. From a pharmacological perspective, research is driven versus synthetic mannosides: no further considerations are expected on alpha-D-mannose.

Fimbria targeting superparamagnetic iron oxide nanoparticles enhance the antimicrobial and antibiofilm activity of ciprofloxacin against quinolone-resistant E. coli

High quinolone resistance of Escherichia coli limits the therapy options for urinary tract infection (UTI). In response to the urgent need for efficient treatment of multidrug-resistant infections, we designed a fimbriae targeting superparamagnetic iron oxide nanoparticle (SPION) delivering ciprofloxacin to ciprofloxacin-resistant E. coli. Bovine serum albumin (BSA) conjugated poly(acrylic acid) (PAA) coated SPIONs (BSA@PAA@SPION) were developed for encapsulation of ciprofloxacin and the nanoparticles were tagged with 4-aminophenyl-α-D-mannopyrannoside (mannoside, Man) to target E. coli fimbriae. Ciprofloxacin-loaded mannoside tagged nanoparticles (Cip-Man-BSA@PAA@SPION) provided high antibacterial activity (97.1 and 97.5%, respectively) with a dose of 32 μg/mL ciprofloxacin against two ciprofloxacin-resistant E. coli isolates. Furthermore, a strong biofilm inhibition (86.9% and 98.5%, respectively) was achieved in the isolates at a dose 16 and 8 times lower than the minimum biofilm eradication concentration (MBEC) of ciprofloxacin. Weaker growth inhibition was observed with untargeted nanoparticles, Cip-BSA@PAA@SPIONs, confirming that targeting E. coli fimbria with mannoside-tagged nanoparticles increases the ciprofloxacin efficiency to treat ciprofloxacin-resistant E. coli. Enhanced killing activity against ciprofloxacin-resistant E. coli planktonic cells and strong growth inhibition of their biofilms suggest that Cip-Man-BSA@PAA@SPION system might be an alternative and/or complementary therapeutic option for the treatment of quinolone-resistant E. coli infections.

ROMP-based Glycopolymers with High Affinity for Mannose-Binding Lectins

Well-defined, highly reactive poly(norbornenyl azlactone)s of controlled length (number-average degree of polymerization D P n ¯ = 10 to 1,000) were made by ring-opening metathesis polymerization (ROMP) of pure exo-norbornenyl azlactone. These were converted into glycopolymers using a facile postpolymerization modification (PPM) strategy based on click aminolysis of azlactone side groups by amino-functionalized glycosides. Pegylated mannoside, heptyl-mannoside, and pegylated glucoside were used in the PPM. Binding inhibition of the resulting glycopolymers was evaluated against a lectin panel (Bc2L-A, FimH, langerin, DC-SIGN, ConA). Inhibition profiles depended on the sugars and the degrees of polymerization. Glycopolymers from pegylated-mannoside-functionalized polynorbornene, with D P n ¯ = 100, showed strong binding inhibition, with subnanomolar range inhibitory concentrations (IC50s). Polymers surpassed the inhibitory potential of their monovalent analogues by four to five orders of magnitude thanks to a multivalent (synergistic) effect. Sugar-functionalized poly(norbornenyl azlactone)s are therefore promising tools to study multivalent carbohydrate-lectin interactions and for applications against lectin-promoted bacterial/viral binding to host cells.

Effect of Mannan Oligosaccharides Extracts in Uropathogenic Escherichia coli Adhesion in Human Bladder Cells

Urinary tract infections (UTIs) are a common public health problem, mainly caused by uropathogenic Escherichia coli (UPEC). Patients with chronic UTIs are usually treated with long-acting prophylactic antibiotics, which promotes the development of antibiotic-resistant UPEC strains and may complicate their long-term management. D-mannose and extracts rich in D-mannose such as mannan oligosaccharides (MOS; D-mannose oligomers) are promising alternatives to antibiotic prophylaxis due to their ability to inhibit bacterial adhesion to urothelial cells and, therefore, infection. This highlights the therapeutic potential and commercial value of using them as health supplements. Studies on the effect of MOS in UTIs are, however, scarce. Aiming to evaluate the potential benefits of using MOS extracts in UTIs prophylaxis, their ability to inhibit the adhesion of UPEC to urothelial cells and its mechanism of action were assessed. Additionally, the expression levels of the pro-inflammatory marker interleukin 6 (IL-6) were also evaluated. After characterizing their cytotoxic profiles, the preliminary results indicated that MOS extracts have potential to be used for the handling of UTIs and demonstrated that the mechanism through which they inhibit bacterial adhesion is through the competitive inhibition of FimH adhesins through the action of mannose, validated by a bacterial growth impact assessment.

Glycomimetics for the inhibition and modulation of lectins

Carbohydrates are essential mediators of many processes in health and disease. They regulate self-/non-self- discrimination, are key elements of cellular communication, cancer, infection and inflammation, and determine protein folding, function and life-times. Moreover, they are integral to the cellular envelope for microorganisms and participate in biofilm formation. These diverse functions of carbohydrates are mediated by carbohydrate-binding proteins, lectins, and the more the knowledge about the biology of these proteins is advancing, the more interfering with carbohydrate recognition becomes a viable option for the development of novel therapeutics. In this respect, small molecules mimicking this recognition process become more and more available either as tools for fostering our basic understanding of glycobiology or as therapeutics. In this review, we outline the general design principles of glycomimetic inhibitors (Section 2). This section is then followed by highlighting three approaches to interfere with lectin function, i.e. with carbohydrate-derived glycomimetics (Section 3.1), novel glycomimetic scaffolds (Section 3.2) and allosteric modulators (Section 3.3). We summarize recent advances in design and application of glycomimetics for various classes of lectins of mammalian, viral and bacterial origin. Besides highlighting design principles in general, we showcase defined cases in which glycomimetics have been advanced to clinical trials or marketed. Additionally, emerging applications of glycomimetics for targeted protein degradation and targeted delivery purposes are reviewed in Section 4.

Outer Membrane Vesicles (OMVs) as Biomedical Tools and Their Relevance as Immune-Modulating Agents against H. pylori Infections: Current Status and Future Prospects

Outer membrane vesicles (OMVs) are lipid-membrane-bounded nanoparticles that are released from Gram-negative bacteria via vesiculation of the outer membrane. They have vital roles in different biological processes and recently, they have received increasing attention as possible candidates for a broad variety of biomedical applications. In particular, OMVs have several characteristics that enable them to be promising candidates for immune modulation against pathogens, such as their ability to induce the host immune responses given their resemblance to the parental bacterial cell. Helicobacter pylori (H. pylori) is a common Gram-negative bacterium that infects half of the world's population and causes several gastrointestinal diseases such as peptic ulcer, gastritis, gastric lymphoma, and gastric carcinoma. The current H. pylori treatment/prevention regimens are poorly effective and have limited success. This review explores the current status and future prospects of OMVs in biomedicine with a special focus on their use as a potential candidate in immune modulation against H. pylori and its associated diseases. The emerging strategies that can be used to design OMVs as viable immunogenic candidates are discussed.

Biofilm and wound healing: from bench to bedside

The bubbling community of microorganisms, consisting of diverse colonies encased in a self-produced protective matrix and playing an essential role in the persistence of infection and antimicrobial resistance, is often referred to as a biofilm. Although apparently indolent, the biofilm involves not only inanimate surfaces but also living tissue, making it truly ubiquitous. The mechanism of biofilm formation, its growth, and the development of resistance are ever-intriguing subjects and are yet to be completely deciphered. Although an abundance of studies in recent years has focused on the various ways to create potential anti-biofilm and antimicrobial therapeutics, a dearth of a clear standard of clinical practice remains, and therefore, there is essentially a need for translating laboratory research to novel bedside anti-biofilm strategies that can provide a better clinical outcome. Of significance, biofilm is responsible for faulty wound healing and wound chronicity. The experimental studies report the prevalence of biofilm in chronic wounds anywhere between 20 and 100%, which makes it a topic of significant concern in wound healing. The ongoing scientific endeavor to comprehensively understand the mechanism of biofilm interaction with wounds and generate standardized anti-biofilm measures which are reproducible in the clinical setting is the challenge of the hour. In this context of "more needs to be done", we aim to explore various effective and clinically meaningful methods currently available for biofilm management and how these tools can be translated into safe clinical practice.

Emerging Non-Antibiotic Options Targeting Uropathogenic Mechanisms for Recurrent Uncomplicated Urinary Tract Infection

Urinary tract infections (UTIs) are the most frequent bacterial infections in the clinical setting. Even without underlying anatomic or functional abnormalities, more than 40% of women experience at least one UTI in their lifetime, of which 30% develop recurrent UTIs (rUTIs) within 6 months. Conventional management with antibiotics for rUTIs may eventually lead to the development of multidrug-resistant uropathogens. Targeting of the pathogenicity of rUTIs, the evolution of uropathogenic Escherichia coli (UPEC), and inadequate host defenses by immune responses should be explored to provide non-antibiotic solutions for the management of rUTIs. The adaptive evolution of UPEC has been observed in several aspects, including colonization, attachment, invasion, and intracellular replication to invade the urothelium and survive intracellularly. Focusing on the antivirulence of UPEC and modulating the immunity of susceptible persons, researchers have provided potential alternative solutions in four categories: antiadhesive treatments (i.e., cranberries and D-mannose), immunomodulation therapies, vaccines, and prophylaxis with topical estrogen therapy and probiotics (e.g., Lactobacillus species). Combination therapies targeting multiple pathogenic mechanisms are expected to be a future trend in UTI management, although some of these treatment options have not been well established in terms of their long-term efficacy. Additional clinical trials are warranted to validate the therapeutic efficacy and durability of these techniques.

Glycopolymers against pathogen infection

Pathogens including viruses, bacteria, fungi, and parasites continue to shape our lives in profound ways every day. As we have learned to live in parallel with pathogens, we have gained a better understanding of the rules of engagement for how they bind, adhere, and invade host cells. One such mechanism involves the exploitation of host cell surface glycans for attachment/adhesion, one of the first steps of infection. This knowledge has led to the development of glycan-based diagnostics and therapeutics for the treatment and prevention of infection. One class of compounds that has become increasingly important are the glycopolymers. Glycopolymers are macromolecules composed of a synthetic scaffold presenting carbohydrates as side chain motifs. Glycopolymers are particularly attractive because their properties can be tuned by careful choice of the scaffold, carbohydrate/glycan, and overall presentation. In this review, we highlight studies over the past ten years that have examined the role of glycopolymers in pathogen adhesion and host cell infection, biofilm formation and removal, and drug delivery with the aim of examining the direct effects of these macromolecules on pathogen engagement. In addition, we also examine the role of glycopolymers as diagnostics for the detection and monitoring of pathogens.

Configuration-Specific Antibody for Bacterial Heptosylation: An Antiadhesion Therapeutic Strategy

Alternative antibacterial therapies refractory to existing mechanisms of antibiotic resistance are urgently needed. One such attractive therapy is to inhibit bacterial adhesion and colonization. Ser O-heptosylation (Ser O-Hep) on autotransporters of Gram-negative bacteria is a novel glycosylation and has been proven to be essential for bacterial colonization. Herein, we chemically synthesized glycopeptides containing this atypical glycan structure and an absolute C6 configuration through the assembly of Ser O-Hep building blocks. Using glycopeptides as haptens, we generated first-in-class poly- and monoclonal antibodies, termed Anti-Ser^Hep1a and Anti-Ser^Hep1b, that stereoselectively recognize Ser O-heptosylation (d/l-glycero) with high specificity in vitro and in vivo. Importantly, these antibodies effectively blocked diffusely adhering Escherichia coli 2787 adhesion to HeLa cells and in mice in a dose- and Ser O-Hep-dependent manner. Together, these antibodies represent not only useful tools for the discovery of unknown serine O-heptosylated proteins bearing various C6 chiral centers but also a novel class of antiadhesion therapeutic agents for the treatment of bacterial infection.

Current Promising Strategies against Antibiotic-Resistant Bacterial Infections

Infections caused by antibiotic-resistant bacteria (ARB) are one of the major global health challenges of our time. In addition to developing new antibiotics to combat ARB, sensitizing ARB, or pursuing alternatives to existing antibiotics are promising options to counter antibiotic resistance. This review compiles the most promising anti-ARB strategies currently under development. These strategies include the following: (i) discovery of novel antibiotics by modification of existing antibiotics, screening of small-molecule libraries, or exploration of peculiar places; (ii) improvement in the efficacy of existing antibiotics through metabolic stimulation or by loading a novel, more efficient delivery systems; (iii) development of alternatives to conventional antibiotics such as bacteriophages and their encoded endolysins, anti-biofilm drugs, probiotics, nanomaterials, vaccines, and antibody therapies. Clinical or preclinical studies show that these treatments possess great potential against ARB. Some anti-ARB products are expected to become commercially available in the near future.

Recent Advances in the Control of Clinically Important Biofilms

Biofilms are complex structures formed by bacteria, fungi, or even viruses on biotic and abiotic surfaces, and they can be found in almost any part of the human body. The prevalence of biofilm-associated diseases has increased in recent years, mainly because of the frequent use of indwelling medical devices that create opportunities for clinically important bacteria and fungi to form biofilms either on the device or on the neighboring tissues. As a result of their resistance to antibiotics and host immunity factors, biofilms have been associated with the development or persistence of several clinically important diseases. The inability to completely eradicate biofilms drastically increases the burden of disease on both the patient and the healthcare system. Therefore, it is crucial to develop innovative ways to tackle the growth and development of biofilms. This review focuses on dental- and implant-associated biofilm infections, their prevalence in humans, and potential therapeutic intervention strategies, including the recent advances in pharmacology and biomedical engineering. It lists current strategies used to control the formation of clinically important biofilms, including novel antibiotics and their carriers, antiseptics and disinfectants, small molecule anti-biofilm agents, surface treatment strategies, and nanostructure functionalization, as well as multifunctional coatings particularly suitable for providing antibacterial effects to the surface of implants, to treat either dental- or implant-related bacterial infections.

Molecular Factors and Mechanisms Driving Multidrug Resistance in Uropathogenic Escherichia coli-An Update

The rapid emergence of multidrug-resistant (MDR) bacteria indisputably constitutes a major global health problem. Pathogenic Escherichia coli are listed among the most critical group of bacteria that require fast development of new antibiotics and innovative treatment strategies. Among harmful extraintestinal Enterobacteriaceae strains, uropathogenic E. coli (UPEC) pose a significant health threat. UPEC are considered the major causative factor of urinary tract infection (UTI), the second-most commonly diagnosed infectious disease in humans worldwide. UTI treatment places a substantial financial burden on healthcare systems. Most importantly, the misuse of antibiotics during treatment has caused selection of strains with the ability to acquire MDR via miscellaneous mechanisms resulting in gaining resistance against many commonly prescribed antibiotics like ampicillin, gentamicin, cotrimoxazole and quinolones. Mobile genetic elements (MGEs) such as transposons, integrons and conjugative plasmids are the major drivers in spreading resistance genes in UPEC. The co-occurrence of various bacterial evasion strategies involving MGEs and the SOS stress response system requires further research and can potentially lead to the discovery of new, much-awaited therapeutic targets. Here, we analyzed and summarized recent discoveries regarding the role, mechanisms, and perspectives of MDR in the pathogenicity of UPEC.

Small Carbohydrate Derivatives as Potent Antibiofilm Agents

Biofilm formation by most pathogenic bacteria is considered as one of the key mechanisms associated with virulence and antibiotic resistance. Biofilm-forming bacteria adhere to the surfaces of biological or implant medical devices and create communities within their self-produced extracellular matrix that are difficult to treat by existing antibiotics. There is an urgent need to synthesize and screen structurally diverse molecules for their antibiofilm activity that can remove or minimize the bacterial biofilm. The development of carbohydrate-based small molecules as antibiofilm agents holds a great promise in addressing the problem of the eradication of biofilm-related infections. Owing to their structural diversity and specificity, the sugar scaffolds are valuable entities for developing antibiofilm agents. In this perspective, we discuss the literature pertaining to carbohydrate-based natural antibiofilm agents and provide an overview of the design, activity, and mode of action of potent synthetic carbohydrate-based molecules.

Immunomodulation therapy offers new molecular strategies to treat UTI

Innovative solutions are needed for the treatment of bacterial infections, and a range of antibacterial molecules have been explored as alternatives to antibiotics. A different approach is to investigate the immune system of the host for new ways of making the antibacterial defence more efficient. However, the immune system has a dual role as protector and cause of disease: in addition to being protective, increasing evidence shows that innate immune responses can become excessive and cause acute symptoms and tissue pathology during infection. This role of innate immunity in disease suggests that the immune system should be targeted therapeutically, to inhibit over-reactivity. The ultimate goal is to develop therapies that selectively attenuate destructive immune response cascades, while augmenting the protective antimicrobial defence but such treatment options have remained underexplored, owing to the molecular proximity of the protective and destructive effects of the immune response. The concept of innate immunomodulation therapy has been developed successfully in urinary tract infections, based on detailed studies of innate immune activation and disease pathogenesis. Effective, disease-specific, immunomodulatory strategies have been developed by targeting specific immune response regulators including key transcription factors. In acute pyelonephritis, targeting interferon regulatory factor 7 using small interfering RNA or treatment with antimicrobial peptide cathelicidin was protective and, in acute cystitis, targeting overactive effector molecules such as IL-1β, MMP7, COX2, cAMP and the pain-sensing receptor NK1R has been successful in vivo. Furthermore, other UTI treatment strategies, such as inhibiting bacterial adhesion and vaccination, have also shown promise.

Hyperactivation of innate immunity is a disease determinant in urinary tract infections (UTIs). Modulation of innate immunity has promise as a therapy for UTIs. In this Review, the authors discuss potential mechanisms and immunomodulatory therapeutic strategies in UTIs.

Excessive innate immune responses to infection cause symptoms and pathology in acute pyelonephritis and acute cystitis.

Innate immunomodulation therapy is, therefore, a realistic option for treating these conditions.

Targeting excessive innate immune responses at the level of transcription has been successful in animal models.

Innate immunomodulation therapy reduces excessive inflammation and tissue pathology and accelerates bacterial clearance from infected kidneys and bladders in mice.

Innate immunomodulation therapy also accelerates the clearance of antibiotic-resistant bacterial strains.

Characterization of host-pathogen-device interactions in Pseudomonas aeruginosa infection of breast implants

BACKGROUND

Pseudomonas aeruginosa (PA) accounts for 7%-22% of breast implant-associated infections (BIAIs), which can result in reconstructive failures and explantation. Investigating host-pathogen-device interactions in mice and patient samples will improve our understanding of colonization mechanisms, for targeted treatments and clinical guidelines.

METHODS

Mice with and without implants (Mentor®) were infected with PAO1 lab strain or BIP2 or BIP16 clinical strains and sacrificed at 1 day or 7 days post-infection (dpi) to evaluate for colonization of implants and underlying tissues via colony-forming unit (CFU) enumeration. Immunostaining was performed on mouse implants, human tissue expanders (TE) colonized by BIP2, and acellular dermal matrix (ADM) colonized by BIP16.

RESULTS

Colonization of tissues and smooth implants by P. aeruginosa was strain-dependent: at 1dpi, all strains acutely infected tissues with and without implants with colonization levels reflecting growth rates of individual strains. At 7dpi, PAO1 caused colonization of ~105 CFUs/100mg of tissue but required implant presence, while in mice infected with BIP2/BIP16, CFUs were below the limit of detection with or without implants. Immunofluorescence staining of mouse implants, however, demonstrated continued presence of BIP2 and BIP16. Staining showed co-localization of all strains with fibrinogen, collagen I and collagen III on mouse and human samples.

CONCLUSIONS

The trajectory of P. aeruginosa in BIAIs was strain-dependent and strains could exhibit acute symptomatic or chronic asymptomatic colonization. With strains causing clinical symptoms, the presence of an implant significantly worsened infection. For asymptomatic colonizers, further studies investigating their long-term impacts, especially during periods of immunosuppression in hosts, are needed.

Small molecules as next generation biofilm inhibitors and anti-infective agents

Biofilms are consortia of microbes attached to surfaces that could be biotic or abiotic in nature. The bacterial cells are enclosed within a microbial synthesized extrapolymeric substances (EPS). The presence of a thick EPS matrix around the cells, protects it from antimicrobials. As the biofilms are difficult to be eradicated in the tissues and implants, the infections due to biofilms are chronic, persistent as well as recurrent in nature. Biofilm formation in multidrug resistant pathogens is a major public health concern. In this review, we have discussed traditional drug discovery approaches and high throughput screening assays involved in the discovery of small molecules for their application as biofilm inhibitory agents. The small molecules target different phases of biofilm growth in pathogenic bacteria. Here, we have focused on three specific application of small molecules, as anti-adhesion agents that prevent adherence and attachment of cells to surfaces; signal inhibitors that disrupt communication between cells resulting in hampered biofilm growth and development; and finally as agents that induce release of cells from mature biofilms. Some of the biofilm inhibitors have also potentiated the antibiotic efficacy leading to complete eradication of biofilms. It is highly pertinent now to focus on developing these as therapeutics and anti-biofilm agents for coating medical implants and devices in clinical settings.

Longitudinal multi-omics analyses link gut microbiome dysbiosis with recurrent urinary tract infections in women

Recurrent urinary tract infections (rUTIs) are a major health burden worldwide, with history of infection being a significant risk factor. While the gut is a known reservoir for uropathogenic bacteria, the role of the microbiota in rUTI remains unclear. We conducted a year-long study of women with (n = 15) and without (n = 16) history of rUTI, from whom we collected urine, blood and monthly faecal samples for metagenomic and transcriptomic interrogation. During the study 24 UTIs were reported, with additional samples collected during and after infection. The gut microbiome of individuals with a history of rUTI was significantly depleted in microbial richness and butyrate-producing bacteria compared with controls, reminiscent of other inflammatory conditions. However, Escherichia coli gut and bladder populations were comparable between cohorts in both relative abundance and phylogroup. Transcriptional analysis of peripheral blood mononuclear cells revealed expression profiles indicative of differential systemic immunity between cohorts. Altogether, these results suggest that rUTI susceptibility is in part mediated through the gut-bladder axis, comprising gut dysbiosis and differential immune response to bacterial bladder colonization, manifesting in symptoms.

Smart Multifunctional Polymer Systems as Alternatives or Supplements of Antibiotics To Overcome Bacterial Resistance

In recent years, infectious diseases have again become a critical threat to global public health largely due to the challenges posed by antimicrobial resistance. Conventional antibiotics have played a crucial role in combating bacterial infections; however, their efficacy is significantly impaired by widespread drug resistance. Natural antimicrobial peptides (AMPs) and their polymeric mimics demonstrate great potential for killing bacteria with low propensity of resistance as they target the microbial membrane rather than a specific molecular target, but they are also toxic to the host eukaryotic cells. To minimize antibiotics systemic spread and the required dose that promote resistance and to advocate practical realization of the promising activity of AMPs and polymers, smart systems to target bacteria are highly sought after. This review presents bacterial recognition by various specific targeting molecules and the delivery systems of active components in supramolecules. Bacteria-induced activations of antimicrobial-based nanoformulations are also included. Recent advances in the bacteria targeting and delivery of synthetic antimicrobial agents may assist in developing new classes of highly selective antimicrobial systems which can improve bactericidal efficacy and greatly minimize the spread of bacterial resistance.

Bladder epithelial cell phosphate transporter inhibition protects mice against uropathogenic Escherichia coli infection

Urinary tract infections are predominantly caused by uropathogenic Escherichia coli (UPEC). UPEC infects bladder epithelial cells (BECs) via fusiform vesicles, escapes into the cytosol to evade exocytosis, and establishes intracellular bacterial communities (IBCs) for the next round of infection. The UPEC vesicle escape mechanism remains unclear. Here we show that UPEC senses host immune responses and initiates escape by upregulating a key phospholipase. The UPEC phospholipase PldA disrupts the vesicle membrane, and pldA expression is activated by phosphate reduction in vesicles. The host phosphate transporter PIT1 is located on the fusiform vesicle membrane, transporting phosphate into the cytosol. UPEC infection upregulates PIT1 via nuclear factor κB (NF-κB), resulting in phosphate reduction. Silencing PIT1 blocks UPEC vesicle escape in BECs, inhibits IBC formation in mouse bladders, and protects mice from UPEC infection. Our results shed light on pathogenic bacteria responding to intracellular phosphate shortage and tackling host defense and provide insights for development of new therapeutic agents to treat UPEC infection.

Catheter-Associated Urinary Tract Infections: Current Challenges and Future Prospects

Catheter-associated urinary tract infection (CAUTI) is the most common healthcare-associated infection and cause of secondary bloodstream infections. Despite many advances in diagnosis, prevention and treatment, CAUTI remains a severe healthcare burden, and antibiotic resistance rates are alarmingly high. In this review, current CAUTI management paradigms and challenges are discussed, followed by future prospects as they relate to the diagnosis, prevention, and treatment. Clinical and translational evidence will be evaluated, as will key basic science studies that underlie preventive and therapeutic approaches. Novel diagnostic strategies and treatment decision aids under development will decrease the time to diagnosis and improve antibiotic accuracy and stewardship. These include several classes of biomarkers often coupled with artificial intelligence algorithms, cell-free DNA, and others. New preventive strategies including catheter coatings and materials, vaccination, and bacterial interference are being developed and investigated. The antibiotic pipeline remains insufficient, and new strategies for the identification of new classes of antibiotics, and rational design of small molecule inhibitor alternatives, are under development for CAUTI treatment.

Role of D-mannose in urinary tract infections - a narrative review

Urinary tract infections (UTIs) are one of the most prevalent bacterial diseases worldwide. Despite the efficacy of antibiotics targeted against UTI, the recurrence rates remain significant among the patients. Furthermore, the development of antibiotic resistance is a major concern and creates a demand for alternative treatment options. D-mannose, a monosaccharide naturally found in fruits, is commonly marketed as a dietary supplement for reducing the risk for UTIs. Research suggests that supplemented D-mannose could be a promising alternative or complementary remedy especially as a prophylaxis for recurrent UTIs. When excreted in urine, D-mannose potentially inhibits Escherichia coli, the main causative organism of UTIs, from attaching to urothelium and causing infection. In this review, we provide an overview of UTIs, E. coli pathogenesis and D-mannose and outline the existing clinical evidence of D-mannose in reducing the risk of UTI and its recurrence. Furthermore, we discuss the potential effect mechanisms of D-mannose against uropathogenic E.coli.

Recent advances on biomedical applications of bacterial outer membrane vesicles

Nanoscale and non-self-replicating outer membrane vesicles (OMVs) are naturally secreted by some bacteria with their structures and compositions similar to that of the outer membrane of parental bacteria. With some...

Molecular basis for inhibition of adhesin-mediated bacterial-host interactions through a peptide-binding domain

Infections typically begin with pathogens adhering to host cells. For bacteria, this adhesion can occur through specific ligand-binding domains. We identify a 20-kDa peptide-binding domain (PBD) in a 1.5-MDa RTX adhesin of a Gram-negative marine bacterium that colonizes diatoms. The crystal structure of this Ca²⁺-dependent PBD suggests that it may bind the C termini of host cell-surface proteins. A systematic peptide library analysis reveals an optimal tripeptide sequence with 30-nM affinity for the PBD, and X-ray crystallography details its peptide-protein interactions. Binding of the PBD to the diatom partner of the bacteria can be inhibited or competed away by the peptide, providing a molecular basis for inhibiting bacterium-host interactions. We further show that this PBD is found in other bacteria, including human pathogens such as Vibrio cholerae and Aeromonas veronii. Here, we produce the PBD ortholog from A. veronii and demonstrate, using the same peptide inhibitor, how pathogens may be prevented from adhering to their hosts.

Exploiting pilus-mediated bacteria-host interactions for health benefits

Surface pili (or fimbriae) are an important but conspicuous adaptation of several genera and species of Gram-negative and Gram-positive bacteria. These long and non-flagellar multi-subunit adhesins mediate the initial contact that a bacterium has with a host or environment, and thus have come to be regarded as a key colonization factor for virulence activity in pathogens or niche adaptation in commensals. Pili in pathogenic bacteria are well recognized for their roles in the adhesion to host cells, colonization of tissues, and establishment of infection. As an 'anti-adhesive' ploy, targeting pilus-mediated attachment for disruption has become a potentially effective alternative to using antibiotics. In this review, we give a description of the several structurally distinct bacterial pilus types thus far characterized, and as well offer details about the intricacy of their individual structure, assembly, and function. With a molecular understanding of pilus biogenesis and pilus-mediated host interactions also provided, we go on to describe some of the emerging new approaches and compounds that have been recently developed to prevent the adhesion, colonization, and infection of piliated bacterial pathogens.

The microbiome and host mucosal interactions in urinary tract diseases

The urinary tract consists of the bladder, ureters, and kidneys, and is an essential organ system for filtration and excretion of waste products and maintaining systemic homeostasis. In this capacity, the urinary tract is impacted by its interactions with other mucosal sites, including the genitourinary and gastrointestinal systems. Each of these sites harbors diverse ecosystems of microbes termed the microbiota, that regulates complex interactions with the local and systemic immune system. It remains unclear whether changes in the microbiota and associated metabolites may be a consequence or a driver of urinary tract diseases. Here, we review the current literature, investigating the impact of the microbiota on the urinary tract in homeostasis and disease including urinary stones, acute kidney injury, chronic kidney disease, and urinary tract infection. We propose new avenues for exploration of the urinary microbiome using emerging technology and discuss the potential of microbiome-based medicine for urinary tract conditions.

Diagnostic Value of the Fimbriae Distribution Pattern in Localization of Urinary Tract Infection

Urinary tract infections (UTIs) are one of the most common infectious diseases. UTIs are mainly caused by uropathogenic Escherichia coli (UPEC), and are either upper or lower according to the infection site. Fimbriae are necessary for UPEC to adhere to the host uroepithelium, and are abundant and diverse in UPEC strains. Although great progress has been made in determining the roles of different types of fimbriae in UPEC colonization, the contributions of multiple fimbriae to site-specific attachment also need to be considered. Therefore, the distribution patterns of 22 fimbrial genes in 90 UPEC strains from patients diagnosed with upper or lower UTIs were analyzed using PCR. The distribution patterns correlated with the infection sites, an XGBoost model with a mean accuracy of 83.33% and a mean area under the curve (AUC) of the receiver operating characteristic (ROC) of 0.92 demonstrated that fimbrial gene distribution patterns could predict the localization of upper and lower UTIs.

The glycobiology of uropathogenic E. coli infection: the sweet and bitter role of sugars in urinary tract immunity

Urinary tract infections (UTI) are among the most prevalent infectious diseases and the most common cause of nosocomial infections, worldwide. Uropathogenic E. coli (UPEC) are responsible for approximately 80% of all UTI, which most commonly affect the bladder. UPEC colonize the urinary tract by ascension of the urethra, followed by cell invasion, and proliferation inside and outside urothelial cells, thereby causing symptomatic infections and quiescent intracellular reservoirs that may lead to recurrence. Sugars, or glycans, are key molecules for host–pathogen interactions, and UTI are no exception. Surface glycans regulate many of the events associated with UPEC adhesion and infection, as well as induction of the host immune response. While the bacterial protein FimH binds mannose‐containing host glycoproteins to initiate infection and UPEC‐secreted polysaccharides block immune mechanisms to favour intracellular replication, host glycans on the urothelial surface and on secreted glycoproteins prevent or limit infection by inhibiting UPEC adhesion. Given the importance of glycans during UTI, here we review the glycobiology of UPEC infection to highlight fundamental sugar‐mediated processes of immunological interest for their potential clinical applications. Interdisciplinary approaches incorporating glycomics and infection biology may help to develop novel non‐antibiotic‐based therapeutic strategies for bacterial infections as the spread of antimicrobial‐resistant uropathogens is currently threatening modern healthcare systems.

Novel Strategies to Combat Bacterial Biofilms

Biofilms are considered as a severe problem in the treatment of bacterial infections; their development causes some noticeable resistance to antibacterial agents. Biofilms are responsible for at least two-thirds of all infections, displaying promoted resistance to classical antibiotic treatments. Therefore, finding new alternative therapeutic approaches is essential for the treatment and inhibition of biofilm-related infections. Therefore, this review aims to describe the potential therapeutic strategies that can inhibit bacterial biofilm development; these include the usage of antiadhesion agents, AMPs, bacteriophages, QSIs, aptamers, NPs and PNAs, which can prevent or eradicate the formation of biofilms. These antibiofilm agents represent a promising therapeutic target in the treatment of biofilm infections and development of a strong capability to interfere with different phases of the biofilm development, including adherence, polysaccharide intercellular adhesion (PIA), quorum sensing molecules and cell-to-cell connection, bacterial aggregation, planktonic bacteria killing and host-immune response modulation. In addition, these components, in combination with antibiotics, can lead to the development of some kind of powerful combined therapy against bacterial biofilm-related infections.

Structural Basis of Ligand Selectivity by a Bacterial Adhesin Lectin Involved in Multispecies Biofilm Formation

Bacterial adhesins are key virulence factors that are essential for the pathogen-host interaction and biofilm formation that cause most infections. Many of the adhesin-driven cell-cell interactions are mediated by lectins.

Carbohydrate recognition by lectins governs critical host-microbe interactions. MpPA14 (Marinomonas primoryensis PA14 domain) lectin is a domain of a 1.5-MDa adhesin responsible for a symbiotic bacterium-diatom interaction in Antarctica. Here, we show that MpPA14 binds various monosaccharides, with l-fucose and N-acetylglucosamine being the strongest ligands (dissociation constant [K_d], ∼150 μM). High-resolution structures of MpPA14 with 15 different sugars bound elucidated the molecular basis for the lectin’s apparent binding promiscuity but underlying selectivity. MpPA14 mediates strong Ca²⁺-dependent interactions with the 3,4-diols of l-fucopyranose and glucopyranoses, and it binds other sugars via their specific minor isomers. Thus, MpPA14 only binds polysaccharides like branched glucans and fucoidans with these free end groups. Consistent with our findings, adhesion of MpPA14 to diatom cells was selectively blocked by l-fucose, but not by N-acetyl galactosamine. The MpPA14 lectin homolog present in a Vibrio cholerae adhesin was produced and was shown to have the same sugar binding preferences as MpPA14. The pathogen’s lectin was unable to effectively bind the diatom in the presence of fucose, thus demonstrating the antiadhesion strategy of blocking infection via ligand-based antagonists.

On-cell saturation transfer difference NMR for the identification of FimH ligands and inhibitors

We describe the development of an on-cell NMR method for the rapid screening of FimH ligands and the structural identification of ligand binding epitopes. FimH is a mannose-binding bacterial adhesin expressed at the apical end of type 1 pili of uropathogenic bacterial strains and responsible for their d-mannose sensitive adhesion to host mammalian epithelial cells. Because of these properties, FimH is a key virulence factor and an attractive therapeutic target for urinary tract infection. We prepared synthetic d-mannose decorated dendrimers, we tested their ability to prevent the FimH-mediated yeast agglutination, and thus we used the compounds showing the best inhibitory activity as models of FimH multivalent ligands to set up our NMR methodology. Our experimental protocol, based on on-cell STD NMR techniques, is a suitable tool for the screening and the epitope mapping of FimH ligands aimed at the development of new antiadhesive and diagnostic tools against urinary tract infection pathogens. Notably, the study is carried out in a physiological environment, i.e. at the surface of living pathogen cells expressing FimH.

Hexavalent thiofucosides to probe the role of the Aspergillus fumigatus lectin FleA in fungal pathogenicity

Aspergillus fumigatus is a pathogenic fungus infecting the respiratory system and responsible for a variety of life-threatening lung diseases. A fucose-binding lectin named FleA which has a controversial role in A. fumigatus pathogenesis was recently identified. New chemical probes with high affinity and enzymatic stability are needed to explore the role of FleA in the infection process. In this study, we developed potent FleA antagonists based on optimized and non-hydrolysable thiofucoside ligands. We first synthesized a set of monovalent sugars showing micromolar affinity for FleA by isothermal titration calorimetry. The most potent derivative was co-crystallized with FleA to gain insights into the binding mode in operation. Its chemical multimerization on a cyclodextrin scaffold led to an hexavalent compound with a significantly enhanced binding affinity (K_d = 223 ± 21 nM) thanks to a chelate binding mode. The compound could probe the role of bronchial epithelial cells in a FleA-mediated response to tissue invasion.

Considerations on D-mannose Mechanism of Action and Consequent Classification of Marketed Healthcare Products

Urinary tract infections (UTIs) are very common disorders that affect adult women. Indeed, 50% of all women suffer from UTIs at least one time in their lifetime; 20-40% of them experience recurrent episodes. The majority of UTIs seems to be due to uropathogenic Escherichia coli that invades urothelial cells and forms quiescent bacterial reservoirs. Recurrences of UTIs are often treated with non-prescribed antibiotics by the patients, with increased issues connected to antibiotics resistance. D-mannose, a monosaccharide that is absorbed but not metabolized by the human body, has been proposed as an alternative approach for managing UTIs since it can inhibit the bacterial adhesion to the urothelium. This manuscript discusses the mechanisms through which D-mannose acts to highlight the regulatory aspects relevant for determining the administrative category of healthcare products placed on the market. The existing literature permits to conclude that the anti-adhesive effect of D-mannose cannot be considered as a pharmacological effect and, therefore, D-mannose-based products should be classified as medical devices composed of substances.

Discovery of Bacterial Fimbria-Glycan Interactions Using Whole-Cell Recombinant Escherichia coli Expression

Chaperone-usher (CU) fimbriae are the most abundant Gram-negative bacterial fimbriae, with 38 distinct CU fimbria types described in Escherichia coli alone. Some E. coli CU fimbriae have been well characterized and bind to specific glycan targets to confer tissue tropism. For example, type 1 fimbriae bind to α-d-mannosylated glycoproteins such as uroplakins in the bladder via their tip-located FimH adhesin, leading to colonization and invasion of the bladder epithelium. Despite this, the receptor-binding affinity of many other E. coli CU fimbria types remains poorly characterized. Here, we used a recombinant E. coli strain expressing different CU fimbriae, in conjunction with glycan array analysis comprising >300 glycans, to dissect CU fimbria receptor specificity. We initially validated the approach by demonstrating the purified FimH lectin-binding domain and recombinant E. coli expressing type 1 fimbriae bound to a similar set of glycans. This technique was then used to map the glycan binding affinity of six additional CU fimbriae, namely, P, F1C, Yqi, Mat/Ecp, K88, and K99 fimbriae. The binding affinity was determined using whole-bacterial-cell surface plasmon resonance. This work describes new information in fimbrial specificity and a rapid and scalable system to define novel adhesin-glycan interactions that underpin bacterial colonization and disease.

Old problems and new solutions: antibiotic alternatives in food animal production

The antimicrobial resistance crisis is a Global Health challenge that impacts humans, animals, and the environment alike. In response to increased demands for animal protein and by-products, there has been a substantial increase in the use of antimicrobial agents in the animal industry. Indeed, they are extensively used to prevent, control, and (or) treat disease in animals. In addition to infection control, in-feed supplementation with antimicrobials became common practice for growth promotion of livestock. Unfortunately, the global overuse of antimicrobials has contributed to the emergence and spread of resistance. As such, many countries have implemented policies and approaches to eliminate the use of antimicrobials as growth promoters in food animals, which necessitates the need for alternate and One Health strategies to maintain animal health and welfare. This review summarizes the antimicrobial resistance crisis from Global Health and One Health perspectives. In addition, we outline examples of potential alternate strategies to circumvent antimicrobial use in animal husbandry practices, including antivirulence agents, bacteriophages, and nutritional measures to control bacterial pathogens. Overall, these alternate strategies require further research and development efforts, including assessment of efficacy and the associated development, manufacturing, and labor costs.

Limited effects of long-term daily cranberry consumption on the gut microbiome in a placebo-controlled study of women with recurrent urinary tract infections

BACKGROUND

Urinary tract infections (UTIs) affect 15 million women each year in the United States, with > 20% experiencing frequent recurrent UTIs. A recent placebo-controlled clinical trial found a 39% reduction in UTI symptoms among recurrent UTI sufferers who consumed a daily cranberry beverage for 24 weeks. Using metagenomic sequencing of stool from a subset of these trial participants, we assessed the impact of cranberry consumption on the gut microbiota, a reservoir for UTI-causing pathogens such as Escherichia coli, which causes > 80% of UTIs.

RESULTS

The overall taxonomic composition, community diversity, carriage of functional pathways and gene families, and relative abundances of the vast majority of observed bacterial taxa, including E. coli, were not changed significantly by cranberry consumption. However, one unnamed Flavonifractor species (OTU41), which represented ≤1% of the overall metagenome, was significantly less abundant in cranberry consumers compared to placebo at trial completion. Given Flavonifractor's association with negative human health effects, we sought to determine OTU41 characteristic genes that may explain its differential abundance and/or relationship to key host functions. Using comparative genomic and metagenomic techniques, we identified genes in OTU41 related to transport and metabolism of various compounds, including tryptophan and cobalamin, which have been shown to play roles in host-microbe interactions.

CONCLUSION

While our results indicated that cranberry juice consumption had little impact on global measures of the microbiome, we found one unnamed Flavonifractor species differed significantly between study arms. This suggests further studies are needed to assess the role of cranberry consumption and Flavonifractor in health and wellbeing in the context of recurrent UTI.

TRIAL REGISTRATION

Clinical trial registration number: ClinicalTrials.gov NCT01776021 .

Developments in Mannose-Based Treatments for Uropathogenic Escherichia coli-Induced Urinary Tract Infections

During their lifetime almost half of women will experience a symptomatic urinary tract infection (UTI) with a further half experiencing a relapse within six months. Currently UTIs are treated with antibiotics, but increasing antibiotic resistance rates highlight the need for new treatments. Uropathogenic Escherichia coli (UPEC) is responsible for the majority of symptomatic UTI cases and thus has become a key pathological target. Adhesion of type one pilus subunit FimH at the surface of UPEC strains to mannose-saturated oligosaccharides located on the urothelium is critical to pathogenesis. Since the identification of FimH as a therapeutic target in the late 1980s, a substantial body of research has been generated focusing on the development of FimH-targeting mannose-based anti-adhesion therapies. In this review we will discuss the design of different classes of these mannose-based compounds and their utility and potential as UPEC therapeutics.

AOA-2 Derivatives as Outer Membrane Protein A Inhibitors for Treatment of Gram-Negative Bacilli Infections

Previously, we identified that a cyclic hexapeptide AOA-2 inhibited the interaction of Gram-negative bacilli (GNB) like Acinetobacter baumannii, Pseudomonas aeruginosa, and Escherichia coli to host cells thereby preventing the development of infection in vitro and in a murine sepsis peritoneal model. In this work, we aimed to evaluate in vitro a library of AOA-2 derivatives in order to improve the effect of AOA-2 against GNB infections. Ten AOA-2 derivatives were synthetized for the in vitro assays. Their toxicities to human lung epithelial cells (A549 cells) for 24 h were evaluated by determining the A549 cells viability using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. The effect of these peptide derivatives and AOA-2 at 250, 125, 62.5, and 31.25 μg/mL on the attachment of A. baumannii ATCC 17978, P. aeruginosa PAO1 and E. coli ATCC 25922 strains to A549 cells was characterized by adherence and viability assays. None of the 10 derivatives showed toxicity to A549 cells. RW01 and RW06 have reduced more the adherence of ATCC 17978, PAO1 and ATCC 2599 strains to A549 cells when compared with the original compound AOA-2. Moreover, both peptides have increased slightly the viability of infected A549 cells by PAO1 and ATCC 25922 than those observed with AOA-2. Finally, RW01 and RW06 have potentiated the activity of colistin against ATCC 17978 strain in the same level with AOA-2. The optimization program of AOA-2 has generated two derivatives (RW01 and RW06) with best effect against interaction of GNB with host cells, specifically against P. aeruginosa and E. coli.

A host receptor enables type 1 pilus-mediated pathogenesis of Escherichia coli pyelonephritis

Type 1 pili have long been considered the major virulence factor enabling colonization of the urinary bladder by uropathogenic Escherichia coli (UPEC). The molecular pathogenesis of pyelonephritis is less well characterized, due to previous limitations in preclinical modeling of kidney infection. Here, we demonstrate in a recently developed mouse model that beyond bladder infection, type 1 pili also are critical for establishment of ascending pyelonephritis. Bacterial mutants lacking the type 1 pilus adhesin (FimH) were unable to establish kidney infection in male C3H/HeN mice. We developed an in vitro model of FimH-dependent UPEC binding to renal collecting duct cells, and performed a CRISPR screen in these cells, identifying desmoglein-2 as a primary renal epithelial receptor for FimH. The mannosylated extracellular domain of human DSG2 bound directly to the lectin domain of FimH in vitro, and introduction of a mutation in the FimH mannose-binding pocket abolished binding to DSG2. In infected C3H/HeN mice, type 1-piliated UPEC and Dsg2 were co-localized within collecting ducts, and administration of mannoside FIM1033, a potent small-molecule inhibitor of FimH, significantly attenuated bacterial loads in pyelonephritis. Our results broaden the biological importance of FimH, specify the first renal FimH receptor, and indicate that FimH-targeted therapeutics will also have application in pyelonephritis.

Urinary tract infections (UTIs) are among the most common bacterial infections in humans. While much has been discovered about how E. coli cause bladder infections, less is known about the host-pathogen interactions that underlie kidney infection (pyelonephritis). We employed recently developed mouse models to show that bacterial surface fibers called type 1 pili, which bear the adhesive protein FimH and are known to mediate E. coli binding to bladder epithelium, are also required for ascending kidney infection. We developed a cell-culture model of bacterial binding to renal collecting duct, then performed a screen using the gene-editing tool CRISPR to identify the first known FimH receptor in the kidney. This epithelial cell-surface protein, desmoglein-2, was shown to directly bind FimH, and we localized this binding to specific extracellular domains of DSG2. Further, we showed that mannosides, small-molecule FimH inhibitors currently in development to treat bladder infection, are also effective in experimental kidney infection. Our study reveals a novel host-pathogen interaction during pyelonephritis and demonstrates how this interaction may be therapeutically targeted.

On the strong connection between nanoscale adhesion of Yad fimbriae and macroscale attachment of Yad-decorated bacteria to glycosylated, hydrophobic and hydrophilic surfaces

Yad fimbriae are currently viewed as versatile bacterial adhesins able to significantly mediate host or plant-pathogen recognition and contribute to the persistence of Escherichia coli in both the environment and within hosts. To date, however, the underlying adhesion process of Yad fimbriae on surfaces defined by controlled coating chemistries has not been evaluated on the relevant molecular scale. In this work, the interaction forces operational between Yad fimbriae expressed by genetically modified E. coli and self-assembled monolayers (SAM) differing in terms of charge, hydrophobicity or the nature of decorating sugar units are quantified by Single Molecule Force Spectroscopy (SMFS) on the nanoscale. It is found that the adhesion of Yad fimbriae onto probes functionalized with xylose is as strong as that measured with probes decorated with anti-Yad antibodies (ca. 80 to 300 pN). In contrast, the interactions of Yad with galactose, lactose, mannose, -OH, -NH₂, -COOH and -CH₃ terminated SAMs are clearly non-specific. Interpretation of SMFS measurements on the basis of worm-like-chain modeling for polypeptide nanomechanics further leads to the estimates of the maximal extension of Yad fimbriae upon stretching, of their persistence length and of their polydispersity. Finally, we show for the first time a strong correlation between the adhesion properties of Yad-decorated bacteria determined from conventional macroscopic counting methods and the molecular adhesion capacity of Yad fimbriae. This demonstration advocates the effort that should be made to understand on the nanoscale level the interactions between fimbriae and their cognate ligands. The results could further help the design of potential anti-adhesive molecules or surfaces to better fight against the virulence of bacterial pathogens.

Lectin and E. coli Binding to Carbohydrate-Functionalized Oligo(ethylene glycol)-Based Microgels: Effect of Elastic Modulus, Crosslinker and Carbohydrate Density

The synthesis of carbohydrate-functionalized biocompatible poly(oligo(ethylene glycol) methacrylate microgels and the analysis of the specific binding to concanavalin A (ConA) and Escherichia coli (E. coli) is shown. By using different crosslinkers, the microgels' size, density and elastic modulus were varied. Given similar mannose (Man) functionalization degrees, the softer microgels show increased ConA uptake, possibly due to increased ConA diffusion in the less dense microgel network. Furthermore, although the microgels did not form clusters with E. coli in solution, surfaces coated with mannose-functionalized microgels are shown to bind the bacteria whereas galactose (Gal) and unfunctionalized microgels show no binding. While ConA binding depends on the overall microgels' density and Man functionalization degree, E. coli binding to microgels' surfaces appears to be largely unresponsive to changes of these parameters, indicating a rather promiscuous surface recognition and sufficiently strong anchoring to few surface-exposed Man units. Overall, these results indicate that carbohydrate-functionalized biocompatible oligo(ethylene glycol)-based microgels are able to immobilize carbohydrate binding pathogens specifically and that the binding of free lectins can be controlled by the network density.

Biofilms as Promoters of Bacterial Antibiotic Resistance and Tolerance

Multidrug resistant bacteria are a global threat for human and animal health. However, they are only part of the problem of antibiotic failure. Another bacterial strategy that contributes to their capacity to withstand antimicrobials is the formation of biofilms. Biofilms are associations of microorganisms embedded a self-produced extracellular matrix. They create particular environments that confer bacterial tolerance and resistance to antibiotics by different mechanisms that depend upon factors such as biofilm composition, architecture, the stage of biofilm development, and growth conditions. The biofilm structure hinders the penetration of antibiotics and may prevent the accumulation of bactericidal concentrations throughout the entire biofilm. In addition, gradients of dispersion of nutrients and oxygen within the biofilm generate different metabolic states of individual cells and favor the development of antibiotic tolerance and bacterial persistence. Furthermore, antimicrobial resistance may develop within biofilms through a variety of mechanisms. The expression of efflux pumps may be induced in various parts of the biofilm and the mutation frequency is induced, while the presence of extracellular DNA and the close contact between cells favor horizontal gene transfer. A deep understanding of the mechanisms by which biofilms cause tolerance/resistance to antibiotics helps to develop novel strategies to fight these infections.

Does targeting Arg98 of FimH lead to high affinity antagonists?

Bacterial resistance has become an important challenge in the treatment of urinary tract infections. The underlying resistance mechanisms can most likely be circumvented with an antiadhesive approach, antagonizing the lectin FimH located at the tip of fimbriae of uropathogenic E. coli. Here we report on a novel series of FimH antagonists based on the 1-(α-d-mannopyranosyl)-4-phenyl-1,2,3-triazole scaffold, designed to incorporate carboxylic acid or ester functions to interact with FimH Arg98. The most potent representative of the series, ester 11e, displayed a K_d value of 7.6 nM for the lectin domain of FimH with a general conclusion that all esters outperform carboxylates in terms of affinity. Surprisingly, all compounds from this new series exhibited improved binding affinities also for the R98A mutant, indicating another possible interaction contributing to binding. Our study on 1-(α-d-mannopyranosyl)-4-phenyl-1,2,3-triazole-based FimH antagonists offers proof that targeting Arg98 side chain by a "chemical common sense", i.e. by introduction of the acidic moiety to form ionic bond with Arg98 is most likely unsuitable approach to boost FimH antagonists' potency.