Heritable nanosilver resistance in priority pathogen: a unique genetic adaptation and comparison with ionic silver and antibiotics. - Related Documents




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950501.0000Heritable nanosilver resistance in priority pathogen: a unique genetic adaptation and comparison with ionic silver and antibiotics. The past decade has seen the incorporation of antimicrobial nanosilver (NAg) into medical devices, and, increasingly, in everyday 'antibacterial' products. With the continued rise of antibiotic resistant bacteria, there are concerns that these priority pathogens will also develop resistance to the extensively commercialized nanoparticle antimicrobials. Herein, this work reports the emergence of stable resistance traits to NAg in the WHO-listed priority pathogen Staphylococcus aureus, which has previously been suggested to have no, or very low, capacity for silver resistance. With no native presence of genetically encoded silver defence mechanisms, the work showed that the bacterium is dependent on mutation of physiologically essential genes, including those involved in nucleotide synthesis and oxidative stress defence. While some mutations were uniquely associated with resistance to NAg, the study also found common mutations that could be protective against both NAg and ionic silver. This is consistent with the observation of NAg/ionic silver cross-resistance. These mutations were detected following withdrawal of the silver exposure, denoting heritable characteristics that allow for spread of the resistance traits even with discontinued silver use. Heritable silver resistance in priority pathogen cautions that these nanoparticle antimicrobials should only be used as needed, to preserve their efficacy for treating infections.202031930233
954510.9997MDR Pumps as Crossroads of Resistance: Antibiotics and Bacteriophages. At present, antibiotic resistance represents a global problem in modern medicine. In the near future, humanity may face a situation where medicine will be powerless against resistant bacteria and a post-antibiotic era will come. The development of new antibiotics is either very expensive or ineffective due to rapidly developing bacterial resistance. The need to develop alternative approaches to the treatment of bacterial infections, such as phage therapy, is beyond doubt. The cornerstone of bacterial defense against antibiotics are multidrug resistance (MDR) pumps, which are involved in antibiotic resistance, toxin export, biofilm, and persister cell formation. MDR pumps are the primary non-specific defense of bacteria against antibiotics, while drug target modification, drug inactivation, target switching, and target sequestration are the second, specific line of their defense. All bacteria have MDR pumps, and bacteriophages have evolved along with them and use the bacteria's need for MDR pumps to bind and penetrate into bacterial cells. The study and understanding of the mechanisms of the pumps and their contribution to the overall resistance and to the sensitivity to bacteriophages will allow us to either seriously delay the onset of the post-antibiotic era or even prevent it altogether due to phage-antibiotic synergy.202235740141
912620.9997The Exploration of Complement-Resistance Mechanisms of Pathogenic Gram-Negative Bacteria to Support the Development of Novel Therapeutics. Resistance to antibiotics in Bacteria is one of the biggest threats to human health. After decades of attempting to isolate or design antibiotics with novel mechanisms of action against bacterial pathogens, few approaches have been successful. Antibacterial drug discovery is now moving towards targeting bacterial virulence factors, especially immune evasion factors. Gram-negative bacteria present some of the most significant challenges in terms of antibiotic resistance. However, they are also able to be eliminated by the component of the innate immune system known as the complement system. In response, Gram-negative bacteria have evolved a variety of mechanisms by which they are able to evade complement and cause infection. Complement resistance mechanisms present some of the best novel therapeutic targets for defending against highly antibiotic-resistant pathogenic bacterial infections.202236015050
913030.9997Glycopeptide antibiotic resistance. Glycopeptide antibiotics are integral components of the current antibiotic arsenal that is under strong pressures as a result of the emergence of a variety of resistance mechanisms over the past 15 years. Resistance has manifested itself largely through the expression of genes that encode proteins that reprogram cell wall biosynthesis and thus evade the action of the antibiotic in the enterococci, though recently new mechanisms have appeared that afford resistance and tolerance in the more virulent staphylococci and streptococci. Overcoming glycopeptide resistance will require innovative approaches to generate new antibiotics or otherwise to inhibit the action of resistance elements in various bacteria. The chemical complexity of the glycopeptides, the challenges of discovering and successfully exploiting new targets, and the growing number of distinct resistance types all increase the difficulty of the current problem we face as a result of the emergence of glycopeptide resistance.200211807177
950640.9997Nisin resistance in Gram-positive bacteria and approaches to circumvent resistance for successful therapeutic use. Antibiotic resistance among bacterial pathogens is one of the most worrying problems in health systems today. To solve this problem, bacteriocins from lactic acid bacteria, especially nisin, have been proposed as an alternative for controlling multidrug-resistant bacteria. Bacteriocins are antimicrobial peptides that have activity mainly against Gram-positive strains. Nisin is one of the most studied bacteriocins and is already approved for use in food preservation. Nisin is still not approved for human clinical use, but many in vitro studies have shown its therapeutic effectiveness, especially for the control of antibiotic-resistant strains. Results from in vitro studies show the emergence of nisin-resistant bacteria after exposure to nisin. Considering that nisin has shown promising results for clinical use, studies to elucidate nisin-resistant mechanisms and the development of approaches to circumvent nisin-resistance are important. Thus, the objectives of this review are to identify the Gram-positive bacterial strains that have shown resistance to nisin, describe their resistance mechanisms and propose ways to overcome the development of nisin-resistance for its successful clinical application.202133689548
954150.9997The Role of the Hfq Protein in Bacterial Resistance to Antibiotics: A Narrative Review. The antibiotic resistance of pathogenic microorganisms is currently one of most major medical problems, causing a few million deaths every year worldwide due to untreatable bacterial infections. Unfortunately, the prognosis is even worse, as over 8 million deaths associated with antibiotic resistance are expected to occur in 2050 if no new effective antibacterial treatments are discovered. The Hfq protein has been discovered as a bacterial RNA chaperone. However, subsequent studies have indicated that this small protein (composed of 102 amino acid residues in Escherichia coli) has more activities, including binding to DNA and influencing its compaction, interaction with biological membranes, formation of amyloid-like structures, and others. Although Hfq is known to participate in many cellular processes, perhaps surprisingly, only reports from recent years have demonstrated its role in bacterial antibiotic resistance. The aim of this narrative review is to discuss how can Hfq affects antibiotic resistance in bacteria and propose how this knowledge may facilitate developing new therapeutic strategies against pathogenic bacteria. We indicate that the mechanisms by which the Hfq protein modulates the response of bacterial cells to antibiotics are quite different, from the regulation of the expression of genes coding for proteins directly involved in antibiotic transportation or action, through direct effects on membranes, to controlling the replication or transposition of mobile genetic elements bearing antibiotic resistance genes. Therefore, we suggest that Hfq could be considered a potential target for novel antimicrobial compounds. We also discuss difficulties in developing such drugs, but since Hfq appears to be a promising target for drugs that may enhance the efficacy of antibiotics, we propose that works on such potential therapeutics are encouraged.202540005731
424760.9997Drug resistance in tuberculosis. Drug-resistant tuberculosis remains a worldwide problem. New laboratory methods have improved our ability to more rapidly identify resistant strains, but the most effective approach is to prevent the appearance of resistance by appropriate choice of antibiotics and directly-observed therapy. Mycobacterium tuberculosis is treated with familiar and unique drugs; consequently, mechanisms of resistance have some unique features. All drug resistance thus far identified develops by mutational events rather than acquisition of resistance genes from other bacteria. An agenda is presented for countering the appearance of further drug resistance in mycobacteria.19979421707
424670.9997Bacteriocins to Thwart Bacterial Resistance in Gram Negative Bacteria. An overuse of antibiotics both in human and animal health and as growth promoters in farming practices has increased the prevalence of antibiotic resistance in bacteria. Antibiotic resistant and multi-resistant bacteria are now considered a major and increasing threat by national health agencies, making the need for novel strategies to fight bugs and super bugs a first priority. In particular, Gram-negative bacteria are responsible for a high proportion of nosocomial infections attributable for a large part to Enterobacteriaceae, such as pathogenic Escherichia coli, Klebsiella pneumoniae, and Pseudomonas aeruginosa. To cope with their highly competitive environments, bacteria have evolved various adaptive strategies, among which the production of narrow spectrum antimicrobial peptides called bacteriocins and specifically microcins in Gram-negative bacteria. They are produced as precursor peptides that further undergo proteolytic cleavage and in many cases more or less complex posttranslational modifications, which contribute to improve their stability and efficiency. Many have a high stability in the gastrointestinal tract where they can target a single pathogen whilst only slightly perturbing the gut microbiota. Several microcins and antibiotics can bind to similar bacterial receptors and use similar pathways to cross the double-membrane of Gram-negative bacteria and reach their intracellular targets, which they also can share. Consequently, bacteria may use common mechanisms of resistance against microcins and antibiotics. This review describes both unmodified and modified microcins [lasso peptides, siderophore peptides, nucleotide peptides, linear azole(in)e-containing peptides], highlighting their potential as weapons to thwart bacterial resistance in Gram-negative pathogens and discusses the possibility of cross-resistance and co-resistance occurrence between antibiotics and microcins in Gram-negative bacteria.202033240239
954380.9997Antisense RNA regulation and application in the development of novel antibiotics to combat multidrug resistant bacteria. Despite the availability of antibiotics and vaccines, infectious diseases remain one of most dangerous threats to humans and animals. The overuse and misuse of antibacterial agents have led to the emergence of multidrug resistant bacterial pathogens. Bacterial cells are often resilient enough to survive in even the most extreme environments. To do so, the organisms have evolved different mechanisms, including a variety of two-component signal transduction systems, which allow the bacteria to sense the surrounding environment and regulate gene expression in order to adapt and respond to environmental stimuli. In addition, some bacteria evolve resistance to antibacterial agents while many bacterial cells are able to acquire resistance genes from other bacterial species to enable them to survive in the presence of toxic antimicrobial agents. The crisis of antimicrobial resistance is an unremitting menace to human health and a burden on public health. The rapid increase in antimicrobial resistant organisms and limited options for development of new classes of antibiotics heighten the urgent need to develop novel potent antibacterial therapeutics in order to combat multidrug resistant infections. In this review, we introduce the regulatory mechanisms of antisense RNA and significant applications of regulated antisense RNA interference technology in early drug discovery. This includes the identification and evaluation of drug targets in vitro and in vivo, the determination of mode of action for antibiotics and new antibacterial agents, as well as the development of peptide-nucleic acid conjugates as novel antibacterials.201323738437
912990.9997Overcoming Intrinsic and Acquired Resistance Mechanisms Associated with the Cell Wall of Gram-Negative Bacteria. The global increase in multi-drug-resistant bacteria is severely impacting our ability to effectively treat common infections. For Gram-negative bacteria, their intrinsic and acquired resistance mechanisms are heightened by their unique cell wall structure. The cell wall, while being a target of some antibiotics, represents a barrier due to the inability of most antibacterial compounds to traverse and reach their intended target. This means that its composition and resulting mechanisms of resistance must be considered when developing new therapies. Here, we discuss potential antibiotic targets within the most well-characterised resistance mechanisms associated with the cell wall in Gram-negative bacteria, including the outer membrane structure, porins and efflux pumps. We also provide a timely update on the current progress of inhibitor development in these areas. Such compounds could represent new avenues for drug discovery as well as adjuvant therapy to help us overcome antibiotic resistance.202032961699
9546100.9997Challenge in the Discovery of New Drugs: Antimicrobial Peptides against WHO-List of Critical and High-Priority Bacteria. Bacterial resistance has intensified in recent years due to the uncontrolled use of conventional drugs, and new bacterial strains with multiple resistance have been reported. This problem may be solved by using antimicrobial peptides (AMPs), which fulfill their bactericidal activity without developing much bacterial resistance. The rapid interaction between AMPs and the bacterial cell membrane means that the bacteria cannot easily develop resistance mechanisms. In addition, various drugs for clinical use have lost their effect as a conventional treatment; however, the synergistic effect of AMPs with these drugs would help to reactivate and enhance antimicrobial activity. Their efficiency against multi-resistant and extensively resistant bacteria has positioned them as promising molecules to replace or improve conventional drugs. In this review, we examined the importance of antimicrobial peptides and their successful activity against critical and high-priority bacteria published in the WHO list.202134064302
9520110.9997Role of Natural Product in Modulation of Drug Transporters and New Delhi Metallo-β Lactamases. A rapid growth in drug resistance has brought options for treating antimicrobial resistance to a halt. Bacteria have evolved to accumulate a multitude of genes that encode resistance for a single drug within a single cell. Alternations of drug transporters are one of the causes for the development of resistance in drug interactions. Conversely, the production of enzymes also inactivates most antibiotics. The discovery of newer classes of antibiotics and drugs from natural products is urgently needed. Alternative medicines play an integral role in countries across the globe but many require validation for treatment strategies. It is essential to explore this chemical diversity in order to find novel drugs with specific activities which can be used as alternative drug targets. This review describes the interaction of drugs with resistant pathogens with a special focus on natural product-derived efflux pump and carbapenemase inhibitors.201930987566
9521120.9997Next-generation strategy for treating drug resistant bacteria: Antibiotic hybrids. Resistance against nearly all antibiotics used clinically have been documented in bacteria. There is an ever-increasing danger caused by multidrug-resistant Gram-negative bacteria in both hospital and community settings. In Gram-negative bacteria, intrinsic resistance to currently available antibiotics is mainly due to overexpressed efflux pumps which are constitutively present and also presence of protective outer membrane. Combination therapy, i.e., use of two or more antibiotics, was thought to be an effective strategy because it took advantage of the additive effects of multiple antimicrobial mechanisms, lower risk of resistance development and lower mortality and improved clinical outcome. However, none of the benefits were seen in in vivo studies. Antibiotic hybrids are being used to challenge the growing drug resistance threat and increase the usefulness of current antibiotic arsenal. Antibiotic hybrids are synthetic constructs of two molecules which are covalently linked. These could be two antibiotics or antibiotic with an adjuvant (efflux pump inhibitor, siderophore, etc.) which increases the access of the antibiotics to the target. The concepts, developments and challenges in the future use of antibiotic hybrids are discussed here. Majority of the studies have been conducted on fluoroquinolones and aminoglycosides molecules. The antibiotic tobramycin has the property to enhance the action of antimicrobial agents against which the multidrug-resistant Gram-negative bacteria were earlier resistant, and thus potentiating the action of legacy antibiotics. Antibiotic hybrids may have a role as the silver bullet in Gram-negative bacteria to overcome drug resistance as well as extend the spectrum of existing antibiotics.201931219074
4433130.9997The Vancomycin Group of Antibiotics and the Fight against Resistant Bacteria. A last line of defence against "superbugs" are the vancomycin group antibiotics. This review describes the determination of their mode of action, and a mechanism of resistance to them. Remarkably, this mechanism of resistance can be overcome without directly modifying the binding site of the antibiotics for the cell-wall precursors of pathogenic bacteria.199929711719
9547140.9997Confronting antibiotic-resistant pathogens: Distinctive drug delivery potentials of progressive nanoparticles. Antimicrobial resistance arises over time, usually due to genetic modifications. Global observations of high resistance rates to popular antibiotics used to treat common bacterial diseases, such as diarrhea, STIs, sepsis, and urinary tract infections, indicate that our supply of effective antibiotics is running low. The mechanisms of action of several antibiotic groups are covered in this review. Antimicrobials disrupt the development and metabolism of bacteria, leading to their eventual death. However, in recent years, microorganisms become resistant to the drugs. Bacteria encode resistant genes against antibiotics and inhibit the function of antibiotics by reducing the uptake of drugs, modifying the enzyme's active site, synthesizing enzymes to degrade antibiotics, and changing the structure of ribosomal subunits. Additionally, the methods of action of resistant bacteria against different kinds of antibiotics as well as their modes of action are discussed. Besides, the resistant pathogenic bacteria which get the most priority by World Health Organisation (WHO) for synthesizing new drugs, have also been incorporated. To overcome antimicrobial resistance, nanomaterials are used to increase the efficacy of antimicrobial drugs. Metallic, inorganic, and polymer-based nanoparticles once conjugated with antibacterial drugs, exhibit synergistic effects by increasing the efficacy of the drugs by inhibiting bacterial growth. Nanomaterial's toxic properties are proportional to their concentrations. Higher concentration nanomaterials are more toxic to the cells. In this review, the toxic properties of nanomaterials on lung cells, lymph nodes, and neuronal cells are also summarized.202438097117
9544150.9997Nano-Strategies to Fight Multidrug Resistant Bacteria-"A Battle of the Titans". Infectious diseases remain one of the leading causes of morbidity and mortality worldwide. The WHO and CDC have expressed serious concern regarding the continued increase in the development of multidrug resistance among bacteria. Therefore, the antibiotic resistance crisis is one of the most pressing issues in global public health. Associated with the rise in antibiotic resistance is the lack of new antimicrobials. This has triggered initiatives worldwide to develop novel and more effective antimicrobial compounds as well as to develop novel delivery and targeting strategies. Bacteria have developed many ways by which they become resistant to antimicrobials. Among those are enzyme inactivation, decreased cell permeability, target protection, target overproduction, altered target site/enzyme, increased efflux due to over-expression of efflux pumps, among others. Other more complex phenotypes, such as biofilm formation and quorum sensing do not appear as a result of the exposure of bacteria to antibiotics although, it is known that biofilm formation can be induced by antibiotics. These phenotypes are related to tolerance to antibiotics in bacteria. Different strategies, such as the use of nanostructured materials, are being developed to overcome these and other types of resistance. Nanostructured materials can be used to convey antimicrobials, to assist in the delivery of novel drugs or ultimately, possess antimicrobial activity by themselves. Additionally, nanoparticles (e.g., metallic, organic, carbon nanotubes, etc.) may circumvent drug resistance mechanisms in bacteria and, associated with their antimicrobial potential, inhibit biofilm formation or other important processes. Other strategies, including the combined use of plant-based antimicrobials and nanoparticles to overcome toxicity issues, are also being investigated. Coupling nanoparticles and natural-based antimicrobials (or other repurposed compounds) to inhibit the activity of bacterial efflux pumps; formation of biofilms; interference of quorum sensing; and possibly plasmid curing, are just some of the strategies to combat multidrug resistant bacteria. However, the use of nanoparticles still presents a challenge to therapy and much more research is needed in order to overcome this. In this review, we will summarize the current research on nanoparticles and other nanomaterials and how these are or can be applied in the future to fight multidrug resistant bacteria.201830013539
4243160.9996Action and resistance mechanisms of antibiotics: A guide for clinicians. Infections account for a major cause of death throughout the developing world. This is mainly due to the emergence of newer infectious agents and more specifically due to the appearance of antimicrobial resistance. With time, the bacteria have become smarter and along with it, massive imprudent usage of antibiotics in clinical practice has resulted in resistance of bacteria to antimicrobial agents. The antimicrobial resistance is recognized as a major problem in the treatment of microbial infections. The biochemical resistance mechanisms used by bacteria include the following: antibiotic inactivation, target modification, altered permeability, and "bypass" of metabolic pathway. Determination of bacterial resistance to antibiotics of all classes (phenotypes) and mutations that are responsible for bacterial resistance to antibiotics (genetic analysis) are helpful. Better understanding of the mechanisms of antibiotic resistance will help clinicians regarding usage of antibiotics in different situations. This review discusses the mechanism of action and resistance development in commonly used antimicrobials.201729109626
9436170.9996Phenotypic Resistance to Antibiotics. The development of antibiotic resistance is usually associated with genetic changes, either to the acquisition of resistance genes, or to mutations in elements relevant for the activity of the antibiotic. However, in some situations resistance can be achieved without any genetic alteration; this is called phenotypic resistance. Non-inherited resistance is associated to specific processes such as growth in biofilms, a stationary growth phase or persistence. These situations might occur during infection but they are not usually considered in classical susceptibility tests at the clinical microbiology laboratories. Recent work has also shown that the susceptibility to antibiotics is highly dependent on the bacterial metabolism and that global metabolic regulators can modulate this phenotype. This modulation includes situations in which bacteria can be more resistant or more susceptible to antibiotics. Understanding these processes will thus help in establishing novel therapeutic approaches based on the actual susceptibility shown by bacteria during infection, which might differ from that determined in the laboratory. In this review, we discuss different examples of phenotypic resistance and the mechanisms that regulate the crosstalk between bacterial metabolism and the susceptibility to antibiotics. Finally, information on strategies currently under development for diminishing the phenotypic resistance to antibiotics of bacterial pathogens is presented.201327029301
4245180.9996Antimicrobial Resistance in Bacteria: Mechanisms, Evolution, and Persistence. In recent years, we have seen antimicrobial resistance rapidly emerge at a global scale and spread from one country to the other faster than previously thought. Superbugs and multidrug-resistant bacteria are endemic in many parts of the world. There is no question that the widespread use, overuse, and misuse of antimicrobials during the last 80 years have been associated with the explosion of antimicrobial resistance. On the other hand, the molecular pathways behind the emergence of antimicrobial resistance in bacteria were present since ancient times. Some of these mechanisms are the ancestors of current resistance determinants. Evidently, there are plenty of putative resistance genes in the environment, however, we cannot yet predict which ones would be able to be expressed as phenotypes in pathogenic bacteria and cause clinical disease. In addition, in the presence of inhibitory and sub-inhibitory concentrations of antibiotics in natural habitats, one could assume that novel resistance mechanisms will arise against antimicrobial compounds. This review presents an overview of antimicrobial resistance mechanisms, and describes how these have evolved and how they continue to emerge. As antimicrobial strategies able to bypass the development of resistance are urgently needed, a better understanding of the critical factors that contribute to the persistence and spread of antimicrobial resistance may yield innovative perspectives on the design of such new therapeutic targets.202031659373
9127190.9996Antimicrobial Peptides: Virulence and Resistance Modulation in Gram-Negative Bacteria. Growing resistance to antibiotics is one of the biggest threats to human health. One of the possibilities to overcome this resistance is to use and develop alternative molecules such as antimicrobial peptides (AMPs). However, an increasing number of studies have shown that bacterial resistance to AMPs does exist. Since AMPs are immunity molecules, it is important to ensure that their potential therapeutic use is not harmful in the long term. Recently, several studies have focused on the adaptation of Gram-negative bacteria to subinhibitory concentrations of AMPs. Such concentrations are commonly found in vivo and in the environment. It is therefore necessary to understand how bacteria detect and respond to low concentrations of AMPs. This review focuses on recent findings regarding the impact of subinhibitory concentrations of AMPs on the modulation of virulence and resistance in Gram-negative bacteria.202032092866