Recent advances in therapeutic targets identification and development of treatment strategies towards Pseudomonas aeruginosa infections

Harmine acts as a quorum sensing inhibitor decreasing the virulence and antibiotic resistance of Pseudomonas aeruginosa

BACKGROUND

As antimicrobial resistance (AMR) has become a global health crisis, new strategies against AMR infection are urgently needed. Quorum sensing (QS), responsible for bacterial communication and pathogenicity, is among the targets for anti-virulence drugs that thrive as one of the promising treatments against AMR infection.

METHODS

We identified a natural compound, Harmine, through virtual screening based on three QS receptors of Pseudomonas aeruginosa (P. aeruginosa) and explored the effect of Harmine on QS-controlled and pathogenicity-related phenotypes including pyocyanin production, exocellular protease excretion, biofilm formation, and twitching motility of P. aeruginosa PA14. The protective effect of Harmine on Caenorhabditis elegans (C. elegans) and mice infection models was determined and the synergistic effect of Harmine combined with common antibiotics was explored. The underlaying mechanism of Harmine's QS inhibitory effect was illustrated by molecular docking analysis, transcriptomic analysis, and target verification assay.

RESULTS

In vitro results suggested that Harmine possessed QS inhibitory effects on pyocyanin production, exocellular protease excretion, biofilm formation, and twitching motility of P. aeruginosa PA14, and in vivo results displayed Harmine's protective effect on C. elegans and mice infection models. Intriguingly, Harmine increased susceptibility of both PA14 and clinical isolates of P. aeruginosa to polymyxin B and kanamycin when used in combination. Moreover, Harmine down-regulated a series of QS controlled genes associated with pathogenicity and the underlying mechanism may have involved competitively antagonizing autoinducers' receptors LasR, RhlR, and PqsR.

CONCLUSIONS

This study shed light on the anti-virulence potential of Harmine against QS targets, suggesting the possible use of Harmine and its derivates as anti-virulence compounds.

Decoding the TAome and computational insights into parDE toxin-antitoxin systems in Pseudomonas aeruginosa

Toxin-antitoxin (TA) modules are widely found in the genomes of pathogenic bacteria. They regulate vital cellular functions like transcription, translation, and DNA replication, and are therefore essential to the survival of bacteria under stress. With a focus on the type II parDE modules, this study thoroughly examines TAome in Pseudomonas aeruginosa, a bacterium well-known for its adaptability and antibiotic resistance. We explored the TAome in three P. aeruginosa strains: ATCC 27,853, PAO1, and PA14, and found 15 type II TAs in ATCC 27,853, 12 in PAO1, and 13 in PA14, with significant variation in the associated mobile genetic elements. Five different parDE homologs were found by further TAome analysis in ATCC 27,853, and their relationships were confirmed by sequence alignments and precise genomic positions. After comparing these ParDE modules' sequences to those of other pathogenic bacteria, it was discovered that they were conserved throughout many taxa, especially Proteobacteria. Nucleic acids were predicted as potential ligands for ParD antitoxins, whereas ParE toxins interacted with a wide range of small molecules, indicating a diverse functional repertoire. The interaction interfaces between ParDE TAs were clarified by protein-protein interaction networks and docking studies, which also highlighted important residues involved in binding. This thorough examination improves our understanding of the diversity, evolutionary dynamics, and functional significance of TA systems in P. aeruginosa, providing insights into their roles in bacterial physiology and pathogenicity.

Critical review on plant-derived quorum sensing signaling inhibitors in pseudomonas aeruginosa

Pseudomonas aeruginosa, a biofilm-forming organism with complex quorum mechanisms (Las, Rhl, PQS, and IQS), poses an imminent danger to the healthcare sector and renders current treatment options for chemotherapy ineffectual. The pathogen's diverse pathogenicity, antibiotic resistance, and biofilms make it difficult to eradicate it effectively. Quorum sensing, a complex system reliant on cell density, controls P. aeruginosa's pathogenesis. Quorum-sensing genes are key components of P. aeruginosa's pathogenic arsenal, and their expression determines how severe the spread of infection becomes. Over the past ten years, there has been a noticeable increase in the quest for and development of new antimicrobial medications. Quorum sensing may be an effective treatment for infections triggered by bacteria. Introducing quorum-sensing inhibitors as an anti-virulent strategy might be an intriguing therapeutic method that can be effectively employed along with current medications. Amongst the several speculated processes, a unique anti-virulence strategy using anti-quorum sensing and antibiofilm medications for targeting pseudomonal infestations seems to be at the forefront. Due to their noteworthy quorum quenching capabilities, biologically active phytochemicals have become more well-known in the realm of science in this context. Recent research showed how different phytochemical quorum quenching actions affect P. aeruginosa's QS-dependent pathogenicity. This review focuses on the most current data supporting the implementation of plant bio-actives to treat P.aeruginosa-associated diseases, as well as the benefits and future recommendationsof employing them in anti-virulence therapies as a supplementary drug development approach towards conventional antibiotic approaches.

Repression of resistance mechanisms of Pseudomonas aeruginosa: implications of the combination of antibiotics and phytoconstituents

Antimicrobial resistance is a prevalent problem witnessed globally and creating an alarming situation for the treatment of infections caused by resistant pathogens. Available armaments such as antibiotics often fail to exhibit the intended action against resistant pathogens, leading to failure in the treatments that are causing mortality. New antibiotics or a new treatment approach is necessary to combat this situation. P. aeruginosa is an opportunistic drug resistant pathogen and is the sixth most common cause of nosocomial infections. P. aeruginosa due to its genome organization and other factors are exhibiting resistance against drugs. Bacterial biofilm formation, low permeability of outer membrane, the production of the beta-lactamase, and the production of several efflux systems limits the antibacterial potential of several classes of antibiotics. Combination of phytoconstituents with antibiotics is a promising strategy to combat multidrug resistant P. aeruginosa. Phytoconstituents such as flavonoids, terpenoids, alkaloids, polypeptides, phenolics, and essential oils are well known antibacterial agents. In this review, the activity of combination of the phytoconstituents and antibiotics, and their corresponding mechanism of action was discussed elaborately. The combination of antibiotics and plant-derived compounds exhibited better efficacy compared to antibiotics alone against the antibiotic resistance P. aeruginosa infections.

LL37 Microspheres Loaded on Activated Carbon-chitosan Hydrogel: Anti-bacterial and Anti-toxin Wound Dressing for Chronic Wound Infections

Antimicrobial peptide LL37 is a promising antibacterial candidate due to its potent antimicrobial activity with no known bacterial resistance. However, intrinsically LL37 is susceptible to degradation in wound fluids limits its effectiveness. Bacterial toxins which are released after cell lysis are found to hinder wound healing. To address these challenges, encapsulating LL37 in microspheres (MS) and loading the MS onto activated carbon (AC)-chitosan (CS) hydrogel. This advanced wound dressing not only protects LL37 from degradation but also targets bacterial toxins, aiding in the healing of chronic wound infections. First, LL37 MS and LL37-AC-CS hydrogel were prepared and characterised in terms of physicochemical properties, drug release, and peptide-polymer compatibility. Antibacterial and antibiofilm activity, bacterial toxin elimination, cell migration, and cell cytotoxicity activities were investigated. LL37-AC-CS hydrogel was effective against Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus. LL37-AC-CS hydrogel bound more endotoxin than AC with CS hydrogel alone. The hydrogel also induced cell migration after 72 h and showed no cytotoxicity towards NHDF after 72 h of treatment. In conclusion, the LL37-AC-CS hydrogel was shown to be a stable, non-toxic advanced wound dressing method with enhanced antimicrobial and antitoxin activity, and it can potentially be applied to chronic wound infections to accelerate wound healing.

Michael F, Cox A, Sauvageau J. Optimization of the Synthesis and Conjugation of the Methyl Rhamnan Tip of Pseudomonas aeruginosa A-Band Polysaccharide and Immunogenicity Evaluation for the Continued Development of a Potential Glycoconjugate Vaccine

Pseudomonas aeruginosa is an antimicrobial-resistant bacterium that has no vaccine approved for human use. Additionally, it has been identified by the World Health Organization as a priority pathogen for novel vaccines and therapeutic development. We previously developed a synthetic mimic of the A-band polysaccharide tip that showed promise in terms of immunogenicity for use as a glycoconjugate vaccine. In this current manuscript, we improve upon the previous work to continue the development of this glycoconjugate vaccine. Herein, we report a higher-yielding synthesis of mimics containing a handle and a spacer that improved conjugation efficiency, resulting in better carbohydrate-to-protein ratios and also good immunogenicity of these conjugates in mice and rabbits. The data suggested that perhaps only a tetrasaccharide was required to induce an immune response capable of recognizing whole cells of P. aeruginosa.

Antimicrobial resistance of Pseudomonas aeruginosa: navigating clinical impacts, current resistance trends, and innovations in breaking therapies

Pseudomonas aeruginosa, a Gram-negative bacterium, is recognized for its adaptability and opportunistic nature. It poses a substantial challenge in clinical settings due to its complicated antibiotic resistance mechanisms, biofilm formation, and capacity for persistent infections in both animal and human hosts. Recent studies revealed a potential zoonotic transmission of P. aeruginosa between animals, the environment, and human populations which highlights awareness of this microbe. Implementation of the One Health approach, which underscores the connection between human, animal, and environmental health, we aim to offer a comprehensive perspective on the current landscape of P. aeruginosa management. This review presents innovative strategies designed to counteract P. aeruginosa infections. Traditional antibiotics, while effective in many cases, are increasingly compromised by the development of multidrug-resistant strains. Non-antibiotic avenues, such as quorum sensing inhibition, phage therapy, and nanoparticle-based treatments, are emerging as promising alternatives. However, their clinical application encounters obstacles like cost, side effects, and safety concerns. Effectively addressing P. aeruginosa infections necessitates persistent research efforts, advancements in clinical development, and a comprehension of host-pathogen interactions to deal with this resilient pathogen.

The Biofilm Inhibition Properties of Glucosamine Gold Nanoparticles in Combination with Meropenem against Pseudomonas aeruginosa on the Endotracheal Tube: A Model of Biofilm-Related Ventilator-Associated Pneumonia

Biofilm-related infections play a significant role in the development and persistence of ventilator-associated pneumonia. Pseudomonas aeruginosa (P. aeruginosa) frequently causes biofilm-related infections associated with ventilator tubing. Glucosamine gold nanoparticles (AuNPs) may exhibit antibiofilm properties; however, more studies, including combinatorial therapy with antibiotics, are needed to explore their potential applications in clinical settings. This study aims to investigate the biofilm inhibition properties of glucosamine AuNPs in combination with meropenem against P. aeruginosa ATCC 9027 on the endotracheal tube. A biofilm inhibition assay of glucosamine AuNPs at 0.02 mg/mL, both singly and in combination with meropenem at 1 mg/mL, was carried out against P. aeruginosa ATCC 9027 on an endotracheal tube using the tissue culture plate method. Scanning electron microscopy was performed for visualization. Glucosamine AuNPs at 0.02 mg/mL combined with meropenem at 1 mg/mL showed greater biofilm inhibition (72%) on the endotracheal tube than glucosamine nanoparticles at 0.02 mg/mL alone (26%) (p = 0.001). The scanning electron microscopic visualization revealed that the untreated P. aeruginosa biofilm was denser than the glucosamine nanoparticles-treated biofilm, whether combined with meropenem or using glucosamine nanoparticles alone. The combination of glucosamine AuNPs and meropenem may have the synergistic effect of inhibiting biofilm production of P. aeruginosa on the endotracheal tubes of patients with mechanical ventilation. Conducting additional experiments to explore the impact of combining glucosamine-coated gold nanoparticles (AuNPs) with meropenem on the inhibition of biofilm production by clinical P. aeruginosa isolates would be beneficial.

Minimalist Tetrazine N-Acetyl Muramic Acid Probes for Rapid and Efficient Labeling of Commensal and Pathogenic Peptidoglycans in Living Bacterial Culture and During Macrophage Invasion

N-Acetyl muramic acid (NAM) probes containing alkyne or azide groups are commonly used to investigate aspects of cell wall synthesis because of their small size and ability to incorporate into bacterial peptidoglycan (PG). However, copper-catalyzed alkyne-azide cycloaddition (CuAAC) reactions are not compatible with live cells, and strain-promoted alkyne-azide cycloaddition (SPAAC) reaction rates are modest and, therefore, not as desirable for tracking the temporal alterations of bacterial cell growth, remodeling, and division. Alternatively, the tetrazine-trans-cyclooctene ligation (Tz-TCO), which is the fastest known bioorthogonal reaction and not cytotoxic, allows for rapid live-cell labeling of PG at biologically relevant time scales and concentrations. Previous work to increase reaction kinetics on the PG surface by using tetrazine probes was limited because of low incorporation of the probe. Described here are new approaches to construct a minimalist tetrazine (Tz)-NAM probe utilizing recent advancements in asymmetric tetrazine synthesis. This minimalist Tz-NAM probe was successfully incorporated into pathogenic and commensal bacterial PG where fixed and rapid live-cell, no-wash labeling was successful in both free bacterial cultures and in coculture with human macrophages. Overall, this probe allows for expeditious labeling of bacterial PG, thereby making it an exceptional tool for monitoring PG biosynthesis for the development of new antibiotic screens. The versatility and selectivity of this probe will allow for real-time interrogation of the interactions of bacterial pathogens in a human host and will serve a broader utility for studying glycans in multiple complex biological systems.

Characterization of the dispirotripiperazine derivative PDSTP as antibiotic adjuvant and antivirulence compound against Pseudomonas aeruginosa

Pseudomonas aeruginosa is a major human pathogen, able to establish difficult-to-treat infections in immunocompromised and people with cystic fibrosis (CF). The high rate of antibiotic treatment failure is due to its notorious drug resistance, often mediated by the formation of persistent biofilms. Alternative strategies, capable of overcoming P. aeruginosa resistance, include antivirulence compounds which impair bacterial pathogenesis without exerting a strong selective pressure, and the use of antimicrobial adjuvants that can resensitize drug-resistant bacteria to specific antibiotics. In this work, the dispirotripiperazine derivative PDSTP, already studied as antiviral, was characterized for its activity against P. aeruginosa adhesion to epithelial cells, its antibiotic adjuvant ability and its biofilm inhibitory potential. PDSTP was effective in impairing the adhesion of P. aeruginosa to various immortalized cell lines. Moreover, the combination of clinically relevant antibiotics with the compound led to a remarkable enhancement of the antibiotic efficacy towards multidrug-resistant CF clinical strains. PDSTP-ceftazidime combination maintained its efficacy in vivo in a Galleria mellonella infection model. Finally, the compound showed a promising biofilm inhibitory activity at low concentrations when tested both in vitro and using an ex vivo pig lung model. Altogether, these results validate PDSTP as a promising compound, combining the ability to decrease P. aeruginosa virulence by impairing its adhesion and biofilm formation, with the capability to increase antibiotic efficacy against antibiotic resistant strains.

Optimized preparation pipeline for emergency phage therapy against Pseudomonas aeruginosa at Yale University

Bacteriophage therapy is one potential strategy to treat antimicrobial resistant or persistent bacterial infections, and the year 2021 marked the centennial of Felix d'Hérelle's first publication on the clinical applications of phages. At the Center for Phage Biology & Therapy at Yale University, a preparatory modular approach has been established to offer safe and potent phages for single-patient investigational new drug applications while recognizing the time constraints imposed by infection(s). This study provides a practical walkthrough of the pipeline with an Autographiviridae phage targeting Pseudomonas aeruginosa (phage vB_PaeA_SB, abbreviated to ΦSB). Notably, a thorough phage characterization and the evolutionary selection pressure exerted on bacteria by phages, analogous to antibiotics, are incorporated into the pipeline.

Efficacy of a Mexican folk remedy containing cuachalalate (Amphipterygium adstringens (Schltdl.) Schiede ex Standl) for the treatment of burn wounds infected with Pseudomonas aeruginosa

ETHNOPHARMACOLOGICAL RELEVANCE

Cuachalalate (Amphipterygium adstringens) stem bark has been used to heal wounds and counteract microbial infections since pre-Hispanic times. However, its effect in treating infected burns remains unclear.

STUDY OBJECTIVES

To determine the antipathogenic capacity of a folk remedy (FR) containing cuachalalate stem bark to treat lesions caused by thermal damage and bacterial infection.

MATERIALS AND METHODS

The antipathogenic capacity of the hexanic extract (HE) and FR was evaluated in a burned mouse model infected with Pseudomonas aeruginosa. Second to third-degree burns were induced with 95 °C water in CD1 mice in similar ratios of males to females. The mice were randomly grouped into non-inoculated (Group 1) and P. aeruginosa inoculated. The latter were divided into untreated infection (Group 2) and infection topically treated with HE (Group 3), silver sulfadiazine (Group 4), and tween 80 (Group 5). In the case of FR, the lesions were washed with an aqueous extract (AE) and applied powdered stem bark (Group 6). Animal survival, establishment of the bacteria in the lesions, and systemic dispersion were determined. In addition, histopathological analysis was performed. The chemical composition of the AE was analyzed through molecular networking analysis, and the antivirulence capacity was determined through the inhibition of pyocyanin production and caseinolytic activity.

RESULTS

Only the FR showed antipathogenic activity and increased animal survival by 50% by reducing the systemic dispersion of P. aeruginosa. In addition, it stimulated the formation of granulation tissue and the generation of new blood vessels. The AE did not show bactericidal activity but reduced bacterial virulence, and glycosylated flavonoids and catechins were identified as its main constituents.

CONCLUSIONS

The results of this study contribute to validating the effectiveness of a popular remedy containing cuachalalate stem bark for treating burns infected with P. aeruginosa.

Aptamers: A Cutting-Edge Approach for Gram-Negative Bacterial Pathogen Identification

Early and accurate diagnoses of pathogenic microorganisms is essential to correctly identify diseases, treating infections, and tracking disease outbreaks associated with microbial infections, to develop precautionary measures that allow a fast and effective response in epidemics and pandemics, thus improving public health. Aptamers are a class of synthetic nucleic acid molecules with the potential to be used for medical purposes, since they can be directed towards any target molecule. Currently, the use of aptamers has increased because they are a useful tool in the detection of specific targets. We present a brief review of the use of aptamers to detect and identify bacteria or even some toxins with clinical importance. This work describes the advances in the technology of aptamers, with the purpose of providing knowledge to develop new aptamers for diagnoses and treatment of different diseases caused by infectious microorganisms.

Antibiotics against Pseudomonas aeruginosa on Human Skin Cell Lines: Determination of the Highest Non-Cytotoxic Concentrations with Antibiofilm Capacity for Wound Healing Strategies

Pseudomonas aeruginosa is one of the most common microorganisms causing infections of severe skin wounds. Antibiotic or antiseptic treatments are crucial to prevent and curb these infections. Antiseptics have been reported to be cytotoxic to skin cells and few studies evaluate the impact of commonly used antibiotics. This study evaluates how clinical antibiotics affect skin cells' viability, proliferation, migration, and cytokine secretion and defines the highest non-cytotoxic concentrations that maintain antibacterial activity. Cell proliferation, viability, and migration were evaluated on cell monolayers. Cytokines related to the wound healing process were determined. The minimum inhibitory concentrations and the impact on bacterial biofilm were assessed. Results showed that 0.02 mg/mL ciprofloxacin and 1 mg/mL meropenem are the highest non-cytotoxic concentrations for fibroblasts and keratinocytes while 1.25 mg/mL amikacin and 0.034 mg/mL colistin do not affect fibroblasts' viability and cytokine secretion but have an impact on keratinocytes. These concentrations are above the minimum inhibitory concentration but only amikacin could eradicate the biofilm. For the other antibiotics, cytotoxic concentrations are needed to eradicate the biofilm. Combinations with colistin at non-cytotoxic concentrations effectively eliminate the biofilm. These results provide information about the concentrations required when administering topical antibiotic treatments on skin lesions, and how these antibiotics affect wound management therapies. This study set the basis for the development of novel antibacterial wound healing strategies such as antibiotic artificial skin substitutes.

The Next Generation of Drug Delivery: Harnessing the Power of Bacteriophages

The use of biomaterials, such as bacteriophages, as drug delivery vehicles (DDVs) has gained increasing interest in recent years due to their potential to address the limitations of conventional drug delivery systems. Bacteriophages offer several advantages as drug carriers, such as high specificity for targeting bacterial cells, low toxicity, and the ability to be engineered to express specific proteins or peptides for enhanced targeting and drug delivery. In addition, bacteriophages have been shown to reduce the development of antibiotic resistance, which is a major concern in the field of antimicrobial therapy. Many initiatives have been taken to take up various payloads selectively and precisely by surface functionalization of the outside or interior of self-assembling viral protein capsids. Bacteriophages have emerged as a promising platform for the targeted delivery of therapeutic agents, including drugs, genes, and imaging agents. They possess several properties that make them attractive as drug delivery vehicles, including their ability to specifically target bacterial cells, their structural diversity, their ease of genetic manipulation, and their biocompatibility. Despite the potential advantages of using bacteriophages as drug carriers, several challenges and limitations need to be addressed. One of the main challenges is the limited host range of bacteriophages, which restricts their use to specific bacterial strains. However, this can also be considered as an advantage, as it allows for precise and targeted drug delivery to the desired bacterial cells. The use of biomaterials, including bacteriophages, as drug delivery vehicles has shown promising potential to address the limitations of conventional drug delivery systems. Further research is needed to fully understand the potential of these biomaterials and address the challenges and limitations associated with their use.

The future of cystic fibrosis treatment: from disease mechanisms to novel therapeutic approaches

With the 2019 breakthrough in the development of highly effective modulator therapy providing unprecedented clinical benefits for over 90% of patients with cystic fibrosis who are genetically eligible for treatment, this rare disease has become a front runner of transformative molecular therapy. This success is based on fundamental research, which led to the identification of the disease-causing CFTR gene and our subsequent understanding of the disease mechanisms underlying the pathogenesis of cystic fibrosis, working together with a continuously evolving clinical research and drug development pipeline. In this Series paper, we focus on advances since 2018, and remaining knowledge gaps in our understanding of the molecular mechanisms of CFTR dysfunction in the airway epithelium and their links to mucus dysfunction, impaired host defences, airway infection, and chronic inflammation of the lungs of people with cystic fibrosis. We review progress in (and the remaining obstacles to) pharmacological approaches to rescue CFTR function, and novel strategies for improved symptomatic therapies for cystic fibrosis, including how these might be applicable to common lung diseases, such as bronchiectasis and chronic obstructive pulmonary disease. Finally, we discuss the promise of genetic therapies and gene editing approaches to restore CFTR function in the lungs of all patients with cystic fibrosis independent of their CFTR genotype, and the unprecedented opportunities to transform cystic fibrosis from a fatal disease to a treatable and potentially curable one.

Enzyme Production and Inhibitory Potential of Pseudomonas aeruginosa: Contrasting Clinical and Environmental Isolates

(1) Background: This study summarizes the findings of two studies investigating the inhibitory effects of Pseudomonas aeruginosa strains from clinical and environmental sources against gram-positive and gram-negative bacteria and fungi. The studies also analyzed the correlation between enzyme production and inhibitory effects to gain insights into the antimicrobial capabilities of P. aeruginosa strains; (2) Methods: Both studies employed similar methodologies, including the use of disk diffusion and well diffusion methods to assess the inhibitory effects of P. aeruginosa strains against target pathogens. Enzyme production was analyzed through various biochemical assays to determine the diversity and frequencies of enzyme secretion among the strains; (3) Results: A comparative analysis of enzyme production in P. aeruginosa strains from clinical sources revealed significant variations in enzyme production, with hemolysin and protease being the most commonly produced enzymes. Gelatinase production showed lower rates, whereas chondroitinase and hyaluronidase were absent or occurred less frequently. In contrast, a comparative analysis of enzyme production in environmental isolates showed different patterns, indicating adaptation to environmental conditions. Pyocyanin production was absent in all environmental isolates. The inhibitory effects against gram-positive and gram-negative bacteria varied among different P. aeruginosa strains, with strain-specific variations observed. Limited inhibitory effects were observed against fungi, primarily toward gram-positive bacteria; (4) Conclusions: The findings highlight the strain-specific nature of inhibitory effects and enzyme production in P. aeruginosa strains. The correlation between enzyme production and inhibitory effects against gram-positive bacteria suggest a potential role of specific enzymes, such as hemolysin and protease, in the antimicrobial activity. The complexity of the relationship between enzyme production and the inhibition of different pathogens requires further investigation. The results emphasize the potential of P. aeruginosa strains as sources for antimicrobial strategies, particularly against gram-positive bacteria. Future research should focus on understanding the mechanisms underlying these inhibitory effects and exploring their therapeutic applications.