Predictable and unpredictable evolution of antibiotic resistance. - Related Documents




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946301.0000Predictable and unpredictable evolution of antibiotic resistance. Evolution of bacteria towards antibiotic resistance is unavoidable as it represents a particular aspect of the general evolution of bacteria. Thus, at the very best, the only hope we can have in the field of resistance is to delay dissemination of resistant bacteria or resistance genes. Resistance to antibiotics in bacteria can result from mutations in resident structural or regulatory genes or from horizontal acquisition of foreign genetic information. In this review, we will consider the predictable future of the relationship between bacteria and antibiotics.200818397243
946510.9999Antimicrobial drug resistance: "Prediction is very difficult, especially about the future". Evolution of bacteria towards resistance to antimicrobial drugs, including multidrug resistance, is unavoidable because it represents a particular aspect of the general evolution of bacteria that is unstoppable. Therefore, the only means of dealing with this situation is to delay the emergence and subsequent dissemination of resistant bacteria or resistance genes. Resistance to antimicrobial drugs in bacteria can result from mutations in housekeeping structural or regulatory genes. Alternatively, resistance can result from the horizontal acquisition of foreign genetic information. The 2 phenomena are not mutually exclusive and can be associated in the emergence and more efficient spread of resistance. This review discusses the predictable future of the relationship between antimicrobial drugs and bacteria.200516318687
946420.9999Why is antibiotic resistance a deadly emerging disease? Evolution of bacteria towards resistance to antimicrobial agents, including multidrug resistance, is unavoidable because it represents a particular aspect of the general evolution of bacteria that is unstoppable. Therefore, the only means of dealing with this situation is to delay the emergence and subsequent dissemination of resistant bacteria or resistance genes. In this review, we will consider the biochemical mechanisms and the genetics that bacteria use to offset antibiotic selective pressure. The data provided are mainly, if not exclusively, taken from the work carried out in the laboratory, although there are numerous other examples in the literature.201626806259
948130.9999Genetic linkage and horizontal gene transfer, the roots of the antibiotic multi-resistance problem. Bacteria carrying resistance genes for many antibiotics are moving beyond the clinic into the community, infecting otherwise healthy people with untreatable and frequently fatal infections. This state of affairs makes it increasingly important that we understand the sources of this problem in terms of bacterial biology and ecology and also that we find some new targets for drugs that will help control this growing epidemic. This brief and eclectic review takes the perspective that we have too long thought about the problem in terms of treatment with or resistance to a single antibiotic at a time, assuming that dissemination of the resistance gene was affected by simple vertical inheritance. In reality antibiotic resistance genes are readily transferred horizontally, even to and from distantly related bacteria. The common agents of bacterial gene transfer are described and also one of the processes whereby nonantibiotic chemicals, specifically toxic metals, in the environment can select for and enrich bacteria with antibiotic multiresistance. Lastly, some speculation is offered on broadening our perspective on this problem to include drugs directed at compromising the ability of the mobile elements themselves to replicate, transfer, and recombine, that is, the three "infrastructure" processes central to the movement of genes among bacteria.200617127524
949240.9999The Search for 'Evolution-Proof' Antibiotics. The effectiveness of antibiotics has been widely compromised by the evolution of resistance among pathogenic bacteria. It would be restored by the development of antibiotics to which bacteria cannot evolve resistance. We first discuss two kinds of 'evolution-proof' antibiotic. The first comprises literally evolution-proof antibiotics to which bacteria cannot become resistant by mutation or horizontal gene transfer. The second category comprises agents to which resistance may arise, but so rarely that it does not become epidemic. The likelihood that resistance to a novel agent will spread is evaluated here by a simple model that includes biological and therapeutic parameters governing the evolution of resistance within hosts and the transmission of resistant strains between hosts. This model leads to the conclusion that epidemic spread is unlikely if the frequency of mutations that confer resistance falls below a defined minimum value, and it identifies potential targets for intervention to prevent the evolution of resistance. Whether or not evolution-proof antibiotics are ever found, searching for them is likely to improve the deployment of new and existing agents by advancing our understanding of how resistance evolves.201829191398
949150.9999Mutation and evolution of antibiotic resistance: antibiotics as promoters of antibiotic resistance? Antibiotic resistance appearance and spread have been classically considered the result of a process of natural selection, directed by the use of antibiotics. Bacteria, that have to face the antibiotic challenge, evolve to acquire resistance and, under this strong selective pressure, only the fittest survive, leading to the spread of resistance mechanisms and resistant clones. Horizontal transference of resistance mechanisms seems to be the main way of antibiotic resistance acquisition. Nevertheless, recent findings on hypermutability and antibiotic-induced hypermutation in bacteria have modified the landscape. Here, we present a review of the last data on molecular mechanisms of hypermutability in bacteria and their relationship with the acquisition of antibiotic resistance. Finally, we discuss the possibility that antibiotics may act not only as selectors for antibiotic resistant bacteria but also as resistance promoters.200212102604
948560.9999Evolution of Drug Resistance in Bacteria. Resistance to antibiotics is an important and timely problem of contemporary medicine. Rapid evolution of resistant bacteria calls for new preventive measures to slow down this process, and a longer-term progress cannot be achieved without a good understanding of the mechanisms through which drug resistance is acquired and spreads in microbial populations. Here, we discuss recent experimental and theoretical advances in our knowledge how the dynamics of microbial populations affects the evolution of antibiotic resistance . We focus on the role of spatial and temporal drug gradients and show that in certain situations bacteria can evolve de novo resistance within hours. We identify factors that lead to such rapid onset of resistance and discuss their relevance for bacterial infections.201627193537
948970.9999The origins of antibiotic resistance. Antibiotics remain one of our most important pharmacological tools for the control of infectious disease. However, unlike most other drugs, the use of antibiotics selects for resistant organisms and erodes their clinical utility. Resistance can emerge within populations of bacteria by mutation and be retained by subsequent selection or by the acquisition of resistance elements laterally from other organisms. The source of these resistance genes is only now being understood. The evidence supports a large bacterial resistome-the collection of all resistance genes and their precursors in both pathogenic and nonpathogenic bacteria. These genes have arisen by various means including self-protection in the case of antibiotic producers, transport of small molecules for various reasons including nutrition and detoxification of noxious chemicals, and to accomplish other goals, such as metabolism, and demonstrate serendipitous selectivity for antibiotics. Regardless of their origins, resistance genes can rapidly move through bacterial populations and emerge in pathogenic bacteria. Understanding the processes that contribute to the evolution and selection of resistance is essential to mange current stocks of antibiotics and develop new ones.201223090593
969680.9999Evolution of resistance in microorganisms of human origin. Resistance to antimicrobials in bacteria results from either evolution of "new" DNA or from variation in existing DNA. Evidence suggests that new DNA did not originate since the use of antibiotics in medicine, but evolved long ago in soil bacteria. This evidence is based on functional and structural homologies of resistance proteins in human pathogens, and resistance proteins or physiological proteins of soil bacteria. Variation in existing DNA has been shown to comprise variations in structural or regulatory genes of the normal chromosome or mutations in already existing plasmid-mediated resistance genes modifying the resistance phenotype. The success of R-determinants in human pathogens was due to their horizontal spread by transformation, transduction and conjugation. Furthermore, transposition has enabled bacteria to efficiently distribute R-determinants between independent DNA-molecules. Since the genetic processes involved in the development of resistance are rare events, the selective pressure exerted by antibiotics has significantly contributed to the overall evolutionary picture. With few exceptions, experimental data about the role of antibiotic usage outside human medicine with respect to the resistance problem in human pathogens are missing. Epidemiological data about the occurrence of resistance in human pathogens seem to indicate that the major contributing factor to the problem we face today was the extensive use of antibiotics in medicine itself.19938212510
424490.9999Molecular mechanisms of antibiotic resistance. Antibiotic-resistant bacteria that are difficult or impossible to treat are becoming increasingly common and are causing a global health crisis. Antibiotic resistance is encoded by several genes, many of which can transfer between bacteria. New resistance mechanisms are constantly being described, and new genes and vectors of transmission are identified on a regular basis. This article reviews recent advances in our understanding of the mechanisms by which bacteria are either intrinsically resistant or acquire resistance to antibiotics, including the prevention of access to drug targets, changes in the structure and protection of antibiotic targets and the direct modification or inactivation of antibiotics.201525435309
9490100.9999The superbugs: evolution, dissemination and fitness. Since the introduction of antibiotics, bacteria have not only evolved elegant resistance mechanisms to thwart their effect, but have also evolved ways in which to disseminate themselves or their resistance genes to other susceptible bacteria. During the past few years, research has revealed not only how such resistance mechanisms have been able to evolve and to rapidly disseminate, but also how bacteria have, in some cases, been able to adapt to this new burden of resistance with little or no cost to their fitness. Such adaptations make the control of these superbugs all the more difficult.199810066531
9493110.9999Regulatory integration of horizontally-transferred genes in bacteria. Horizontal transfer of genetic material is a fact of microbial life and bacteria can obtain new DNA sequences through the processes of conjugation, transduction and transformation. This offers the bacterium the possibility of evolving rapidly by importing new genes that code for new traits that may assist in environmental adaptation. Research in this area has focused in particular on the role of horizontal transfer in the dissemination through bacterial populations of genes for resistance to antimicrobial agents, including antibiotics. It is becoming clear that many other phenotypic characteristics have been acquired through horizontal routes and that these include traits contributing to pathogenesis and symbiosis. An important corollary to the acquisition of new genes is the problem of how best to integrate them in the existing gene regulatory circuits of the recipient so that fitness is not compromised initially and can be enhanced in the future through optimal expression of the new genes.200919273337
9482120.9999Gene flow, mobile genetic elements and the recruitment of antibiotic resistance genes into Gram-negative pathogens. Antibiotics were one of the great discoveries of the 20th century. However, resistance appeared even in the earliest years of the antibiotic era. Antibiotic resistance continues to become worse, despite the ever-increasing resources devoted to combat the problem. One of the most important factors in the development of resistance to antibiotics is the remarkable ability of bacteria to share genetic resources via Lateral Gene Transfer (LGT). LGT occurs on a global scale, such that in theory, any gene in any organism anywhere in the microbial biosphere might be mobilized and spread. With sufficiently strong selection, any gene may spread to a point where it establishes a global presence. From an antibiotic resistance perspective, this means that a resistance phenotype can appear in a diverse range of infections around the globe nearly simultaneously. We discuss the forces and agents that make this LGT possible and argue that the problem of resistance can ultimately only be managed by understanding the problem from a broad ecological and evolutionary perspective. We also argue that human activities are exacerbating the problem by increasing the tempo of LGT and bacterial evolution for many traits that are important to humans.201121517914
9494130.9999Within-Host Mathematical Models of Antibiotic Resistance. Mathematical models have been used to study the spread of infectious diseases from person to person. More recently studies are developing within-host modeling which provides an understanding of how pathogens-bacteria, fungi, parasites, or viruses-develop, spread, and evolve inside a single individual and their interaction with the host's immune system.Such models have the potential to provide a more detailed and complete description of the pathogenesis of diseases within-host and identify other influencing factors that may not be detected otherwise. Mathematical models can be used to aid understanding of the global antibiotic resistance (ABR) crisis and identify new ways of combating this threat.ABR occurs when bacteria respond to random or selective pressures and adapt to new environments through the acquisition of new genetic traits. This is usually through the acquisition of a piece of DNA from other bacteria, a process called horizontal gene transfer (HGT), the modification of a piece of DNA within a bacterium, or through. Bacteria have evolved mechanisms that enable them to respond to environmental threats by mutation, and horizontal gene transfer (HGT): conjugation; transduction; and transformation. A frequent mechanism of HGT responsible for spreading antibiotic resistance on the global scale is conjugation, as it allows the direct transfer of mobile genetic elements (MGEs). Although there are several MGEs, the most important MGEs which promote the development and rapid spread of antimicrobial resistance genes in bacterial populations are plasmids and transposons. Each of the resistance-spread-mechanisms mentioned above can be modeled allowing us to understand the process better and to define strategies to reduce resistance.202438949703
4065140.9999The role of the natural environment in the emergence of antibiotic resistance in gram-negative bacteria. During the past 10 years, multidrug-resistant Gram-negative Enterobacteriaceae have become a substantial challenge to infection control. It has been suggested by clinicians that the effectiveness of antibiotics is in such rapid decline that, depending on the pathogen concerned, their future utility can be measured in decades or even years. Unless the rise in antibiotic resistance can be reversed, we can expect to see a substantial rise in incurable infection and fatality in both developed and developing regions. Antibiotic resistance develops through complex interactions, with resistance arising by de-novo mutation under clinical antibiotic selection or frequently by acquisition of mobile genes that have evolved over time in bacteria in the environment. The reservoir of resistance genes in the environment is due to a mix of naturally occurring resistance and those present in animal and human waste and the selective effects of pollutants, which can co-select for mobile genetic elements carrying multiple resistant genes. Less attention has been given to how anthropogenic activity might be causing evolution of antibiotic resistance in the environment. Although the economics of the pharmaceutical industry continue to restrict investment in novel biomedical responses, action must be taken to avoid the conjunction of factors that promote evolution and spread of antibiotic resistance.201323347633
9488150.9999Minimizing potential resistance: the molecular view. The major contribution of molecular biology to the study of antibiotic resistance has been the elucidation of nearly all biochemical mechanisms of resistance and the routes for dissemination of genetic information among bacteria. In this review, we consider the potential contribution of molecular biology to counteracting the evolution of resistant bacteria. In particular, we emphasize the fact that fundamental approaches have had direct practical effects on minimizing potential resistance: by improving interpretation of resistance phenotypes, by providing more adequate human therapy, by fostering more prudent use of antibiotics, and by allowing the rational design of new drugs that evade existing resistance mechanisms or address unexploited targets.200111524711
9703160.9999Ecology and evolution of antibiotic resistance. The evolution of bacterial pathogens towards antibiotic resistance is not just a relevant problem for human health, but a fascinating example of evolution that can be studied in real time as well. Although most antibiotics are natural compounds produced by environmental microbiota, exposure of bacterial populations to high concentrations of these compounds as the consequence of their introduction for human therapy (and later on for farming) a few decades ago is a very recent situation in evolutionary terms. Resistance genes are originated in environmental bacteria, where they have evolved for millions of years to play different functions that include detoxification, signal trafficking or metabolic functions among others. However, as the consequence of the strong selective pressure exerted by antimicrobials at clinical settings, farms and antibiotic-contaminated natural ecosystems, the selective forces driving the evolution of these potential resistance determinants have changed in the last few decades. Natural ecosystems contain a large number of potential resistance genes; nevertheless, just a few of them are currently present in gene-transfer units and disseminated among pathogens. Along the review, the processes implied in this situation and the consequences for the future evolution of resistance and the environmental microbiota are discussed.200923765924
9295170.9999Biological activities specified by antibiotic resistance plasmids. Bacteria can display resistance to a wide spectrum of noxious agents and environmental conditions, and these properties are often mediated by genes located on extrachromosomal DNA elements called plasmids. Replication, vertical and horizontal transmission and evolution of these elements are discussed, and examples of the genes responsible for the resistance phenotypes are given. Selective forces that drive the evolution of new combinations of bacterial properties of particular importance in clinical situations are analysed.19863542928
9472180.9999Bacteriophage and Bacterial Susceptibility, Resistance, and Tolerance to Antibiotics. Bacteriophages, viruses that infect and replicate within bacteria, impact bacterial responses to antibiotics in complex ways. Recent studies using lytic bacteriophages to treat bacterial infections (phage therapy) demonstrate that phages can promote susceptibility to chemical antibiotics and that phage/antibiotic synergy is possible. However, both lytic and lysogenic bacteriophages can contribute to antimicrobial resistance. In particular, some phages mediate the horizontal transfer of antibiotic resistance genes between bacteria via transduction and other mechanisms. In addition, chronic infection filamentous phages can promote antimicrobial tolerance, the ability of bacteria to persist in the face of antibiotics. In particular, filamentous phages serve as structural elements in bacterial biofilms and prevent the penetration of antibiotics. Over time, these contributions to antibiotic tolerance favor the selection of resistance clones. Here, we review recent insights into bacteriophage contributions to antibiotic susceptibility, resistance, and tolerance. We discuss the mechanisms involved in these effects and address their impact on bacterial fitness.202235890320
9486190.9999Acquired Bacterial Resistance to Antibiotics and Resistance Genes: From Past to Future. The discovery, commercialization, and regular administration of antimicrobial agents have revolutionized the therapeutic paradigm, making it possible to treat previously untreatable and fatal infections. However, the excessive use of antibiotics has led to develop resistance soon after their use in clinical practice, to the point of becoming a global emergency. The mechanisms of bacterial resistance to antibiotics are manifold, including mechanisms of destruction or inactivation, target site modification, or active efflux, and represent the main examples of evolutionary adaptation for the survival of bacterial species. The acquirement of new resistance mechanisms is a consequence of the great genetic plasticity of bacteria, which triggers specific responses that result in mutational adaptation, acquisition of genetic material, or alteration of gene expression, virtually producing resistance to all currently available antibiotics. Understanding resistance processes is critical to the development of new antimicrobial agents to counteract drug-resistant microorganisms. In this review, both the mechanisms of action of antibiotic resistance (AMR) and the antibiotic resistance genes (ARGs) mainly found in clinical and environmental bacteria will be reviewed. Furthermore, the evolutionary background of multidrug-resistant bacteria will be examined, and some promising elements to control or reduce the emergence and spread of AMR will be proposed.202540149034