101
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Echaubard P, Sripa B, Mallory FF, Wilcox BA. The role of evolutionary biology in research and control of liver flukes in Southeast Asia. INFECTION GENETICS AND EVOLUTION 2016; 43:381-97. [PMID: 27197053 DOI: 10.1016/j.meegid.2016.05.019] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/24/2015] [Revised: 05/12/2016] [Accepted: 05/14/2016] [Indexed: 01/04/2023]
Abstract
Stimulated largely by the availability of new technology, biomedical research at the molecular-level and chemical-based control approaches arguably dominate the field of infectious diseases. Along with this, the proximate view of disease etiology predominates to the exclusion of the ultimate, evolutionary biology-based, causation perspective. Yet, historically and up to today, research in evolutionary biology has provided much of the foundation for understanding the mechanisms underlying disease transmission dynamics, virulence, and the design of effective integrated control strategies. Here we review the state of knowledge regarding the biology of Asian liver Fluke-host relationship, parasitology, phylodynamics, drug-based interventions and liver Fluke-related cancer etiology from an evolutionary biology perspective. We consider how evolutionary principles, mechanisms and research methods could help refine our understanding of clinical disease associated with infection by Liver Flukes as well as their transmission dynamics. We identify a series of questions for an evolutionary biology research agenda for the liver Fluke that should contribute to an increased understanding of liver Fluke-associated diseases. Finally, we describe an integrative evolutionary medicine approach to liver Fluke prevention and control highlighting the need to better contextualize interventions within a broader human health and sustainable development framework.
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Affiliation(s)
- Pierre Echaubard
- WHO Collaborating Centre for Research and Control of Opisthorchiasis, Tropical Disease Research laboratory, Department of Experimental Pathology, Faculty of Medicine, Khon Kaen University, Khon Kaen 40002, Thailand; Department of Biology, Laurentian University, Sudbury, Ontario P3E 2C6, Canada; Global Health Asia, Faculty of Public Health, Mahidol University, Bangkok, Thailand.
| | - Banchob Sripa
- WHO Collaborating Centre for Research and Control of Opisthorchiasis, Tropical Disease Research laboratory, Department of Experimental Pathology, Faculty of Medicine, Khon Kaen University, Khon Kaen 40002, Thailand; Liver Fluke and Cholangiocarcinoma Research Center, Department of Parasitology, Khon Kaen University, Khon Kaen 40002, Thailand
| | - Frank F Mallory
- Department of Biology, Laurentian University, Sudbury, Ontario P3E 2C6, Canada
| | - Bruce A Wilcox
- Global Health Asia, Faculty of Public Health, Mahidol University, Bangkok, Thailand; Cummings School of Veterinary Medicine, Tufts University, Medford, MA 02155, USA
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102
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Nunn CL, Wallace I, Beall CM. Connecting evolution, medicine, and public health. Evol Anthropol 2016; 24:127-9. [PMID: 26267433 DOI: 10.1002/evan.21451] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Affiliation(s)
- Charles L Nunn
- Department of Evolutionary Anthropology, Duke Global Health Institute, Triangle Center for Evolutionary Medicine, Duke University, Durham, NC
| | - Ian Wallace
- Department of Anthropology, Stony Brook University, Stony Brook, NY
| | - Cynthea M Beall
- Department of Anthropology, Case Western Reserve University Cleveland, OH
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103
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Oronsky BT, Carter CA, Oronsky AL, Salacz ME, Reid T. "No patient left behind": an alternative to "the War on Cancer" metaphor. Med Oncol 2016; 33:55. [PMID: 27129923 DOI: 10.1007/s12032-016-0769-1] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2016] [Accepted: 04/19/2016] [Indexed: 11/29/2022]
Abstract
The War on Cancer began with President Nixon's National Cancer Act of 1971. Treatment-related 'collateral damage' to healthy cells and tissues that reduces quality of life is an unfortunate but inevitable consequence of the overriding imperative to "win the war." In the face of a quality of life decrement, patients are encouraged with militaristic turns-of-phrases to "soldier on," "fight it," and "never say die." Rather than this dysfunctional imagery, which relegates patients to the status of mere cogs in the ever-grinding wheel of the clinical war machine and encourages the practice of disease-centered medicine, we propose an alternate analogy/organizing principle borrowed from the realm of education: No patient left behind.
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Affiliation(s)
- Bryan T Oronsky
- EpicentRx, Inc., 800 W El Camino Real, Suite 180, Mountain View, CA, 94040, USA.
| | - Corey A Carter
- Walter Reed National Military Medical Center, 8901 Wisconsin Ave, Bethesda, MD, 20889, USA
| | - Arnold L Oronsky
- InterWest Partners, 2710 Sand Hill Rd #200, Menlo Park, CA, 94025, USA
| | - Michael E Salacz
- University of Kansas Medical Center, 3901 Rainbow Boulevard, Kansas City, KS, 66160, USA
| | - Tony Reid
- University of California San Diego (UCSD), Moores Cancer Center, 3855 Health Sciences Dr, La Jolla, CA, 92093, USA
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104
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Gjini E, Brito PH. Integrating Antimicrobial Therapy with Host Immunity to Fight Drug-Resistant Infections: Classical vs. Adaptive Treatment. PLoS Comput Biol 2016; 12:e1004857. [PMID: 27078624 PMCID: PMC4831758 DOI: 10.1371/journal.pcbi.1004857] [Citation(s) in RCA: 62] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2015] [Accepted: 03/09/2016] [Indexed: 12/18/2022] Open
Abstract
Antimicrobial resistance of infectious agents is a growing problem worldwide. To prevent the continuing selection and spread of drug resistance, rational design of antibiotic treatment is needed, and the question of aggressive vs. moderate therapies is currently heatedly debated. Host immunity is an important, but often-overlooked factor in the clearance of drug-resistant infections. In this work, we compare aggressive and moderate antibiotic treatment, accounting for host immunity effects. We use mathematical modelling of within-host infection dynamics to study the interplay between pathogen-dependent host immune responses and antibiotic treatment. We compare classical (fixed dose and duration) and adaptive (coupled to pathogen load) treatment regimes, exploring systematically infection outcomes such as time to clearance, immunopathology, host immunization, and selection of resistant bacteria. Our analysis and simulations uncover effective treatment strategies that promote synergy between the host immune system and the antimicrobial drug in clearing infection. Both in classical and adaptive treatment, we quantify how treatment timing and the strength of the immune response determine the success of moderate therapies. We explain key parameters and dimensions, where an adaptive regime differs from classical treatment, bringing new insight into the ongoing debate of resistance management. Emphasizing the sensitivity of treatment outcomes to the balance between external antibiotic intervention and endogenous natural defenses, our study calls for more empirical attention to host immunity processes.
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Affiliation(s)
- Erida Gjini
- Instituto Gulbenkian de Ciência, Oeiras, Portugal
- * E-mail:
| | - Patricia H. Brito
- Instituto Gulbenkian de Ciência, Oeiras, Portugal
- Nova Medical School, Faculdade de Ciências Médicas, Universidade Nova de Lisboa, Lisbon, Portugal
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105
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Legros M, Bonhoeffer S. A combined within-host and between-hosts modelling framework for the evolution of resistance to antimalarial drugs. J R Soc Interface 2016; 13:rsif.2016.0148. [PMID: 27075004 PMCID: PMC4874437 DOI: 10.1098/rsif.2016.0148] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2016] [Accepted: 03/22/2016] [Indexed: 11/25/2022] Open
Abstract
The spread of drug resistance represents a significant challenge to many disease control efforts. The evolution of resistance is a complex process influenced by transmission dynamics between hosts as well as infection dynamics within these hosts. This study aims to investigate how these two processes combine to impact the evolution of resistance in malaria parasites. We introduce a stochastic modelling framework combining an epidemiological model of Plasmodium transmission and an explicit within-human infection model for two competing strains. Immunity, treatment and resistance costs are included in the within-host model. We show that the spread of resistance is generally less likely in areas of intense transmission, and therefore of increased competition between strains, an effect exacerbated when costs of resistance are higher. We also illustrate how treatment influences the spread of resistance, with a trade-off between slowing resistance and curbing disease incidence. We show that treatment coverage has a stronger impact on disease prevalence, whereas treatment efficacy primarily affects resistance spread, suggesting that coverage should constitute the primary focus of control efforts. Finally, we illustrate the importance of feedbacks between modelling scales. Overall, our results underline the importance of concomitantly modelling the evolution of resistance within and between hosts.
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Affiliation(s)
- Mathieu Legros
- ETH Zürich, Institut für Integrative Biologie, 8092 Zürich, Switzerland
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106
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Torres‐Barceló C, Franzon B, Vasse M, Hochberg ME. Long-term effects of single and combined introductions of antibiotics and bacteriophages on populations of Pseudomonas aeruginosa. Evol Appl 2016; 9:583-95. [PMID: 27099623 PMCID: PMC4831460 DOI: 10.1111/eva.12364] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2015] [Accepted: 01/07/2016] [Indexed: 12/25/2022] Open
Abstract
With escalating resistance to antibiotics, there is an urgent need to develop alternative therapies against bacterial pathogens and pests. One of the most promising is the employment of bacteriophages (phages), which may be highly specific and evolve to counter antiphage resistance. Despite an increased understanding of how phages interact with bacteria, we know very little about how their interactions may be modified in antibiotic environments and, reciprocally, how phage may affect the evolution of antibiotic resistance. We experimentally evaluated the impacts of single and combined applications of antibiotics (different doses and different types) and phages on in vitro evolving populations of the opportunistic pathogen Pseudomonas aeruginosa PAO1. We also assessed the effects of past treatments on bacterial virulence in vivo, employing larvae of Galleria mellonella to survey the treatment consequences for the pathogen. We find a strong synergistic effect of combining antibiotics and phages on bacterial population density and in limiting their recovery rate. Our long-term study establishes that antibiotic dose is important, but that effects are relatively insensitive to antibiotic type. From an applied perspective, our results indicate that phages can contribute to managing antibiotic resistance levels, with limited consequences for the evolution of bacterial virulence.
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Affiliation(s)
| | - Blaise Franzon
- Institut des Sciences de l'EvolutionUniversité de MontpellierMontpellierFrance
| | - Marie Vasse
- Institut des Sciences de l'EvolutionUniversité de MontpellierMontpellierFrance
| | - Michael E. Hochberg
- Institut des Sciences de l'EvolutionUniversité de MontpellierMontpellierFrance
- Santa Fe InstituteSanta FeNMUSA
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107
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Bushman M, Morton L, Duah N, Quashie N, Abuaku B, Koram KA, Dimbu PR, Plucinski M, Gutman J, Lyaruu P, Kachur SP, de Roode JC, Udhayakumar V. Within-host competition and drug resistance in the human malaria parasite Plasmodium falciparum. Proc Biol Sci 2016; 283:20153038. [PMID: 26984625 PMCID: PMC4810865 DOI: 10.1098/rspb.2015.3038] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2015] [Accepted: 02/16/2016] [Indexed: 11/12/2022] Open
Abstract
Infections with the malaria parasite Plasmodium falciparum typically comprise multiple strains, especially in high-transmission areas where infectious mosquito bites occur frequently. However, little is known about the dynamics of mixed-strain infections, particularly whether strains sharing a host compete or grow independently. Competition between drug-sensitive and drug-resistant strains, if it occurs, could be a crucial determinant of the spread of resistance. We analysed 1341 P. falciparum infections in children from Angola, Ghana and Tanzania and found compelling evidence for competition in mixed-strain infections: overall parasite density did not increase with additional strains, and densities of individual chloroquine-sensitive (CQS) and chloroquine-resistant (CQR) strains were reduced in the presence of competitors. We also found that CQR strains exhibited low densities compared with CQS strains (in the absence of chloroquine), which may underlie observed declines of chloroquine resistance in many countries following retirement of chloroquine as a first-line therapy. Our observations support a key role for within-host competition in the evolution of drug-resistant malaria. Malaria control and resistance-management efforts in high-transmission regions may be significantly aided or hindered by the effects of competition in mixed-strain infections. Consideration of within-host dynamics may spur development of novel strategies to minimize resistance while maximizing the benefits of control measures.
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Affiliation(s)
- Mary Bushman
- Department of Biology, Emory University, Atlanta, GA 30322, USA Malaria Branch, Division of Parasitic Diseases and Malaria, Center for Global Health, Centers for Disease Control and Prevention, Atlanta, GA 30333, USA
| | - Lindsay Morton
- Malaria Branch, Division of Parasitic Diseases and Malaria, Center for Global Health, Centers for Disease Control and Prevention, Atlanta, GA 30333, USA
| | - Nancy Duah
- Epidemiology Department, Noguchi Memorial Institute for Medical Research, University of Ghana, Legon, Ghana
| | - Neils Quashie
- Epidemiology Department, Noguchi Memorial Institute for Medical Research, University of Ghana, Legon, Ghana Centre for Tropical Clinical Pharmacology and Therapeutics, University of Ghana Medical School, Accra, Ghana
| | - Benjamin Abuaku
- Epidemiology Department, Noguchi Memorial Institute for Medical Research, University of Ghana, Legon, Ghana
| | - Kwadwo A Koram
- Epidemiology Department, Noguchi Memorial Institute for Medical Research, University of Ghana, Legon, Ghana
| | | | - Mateusz Plucinski
- Malaria Branch, Division of Parasitic Diseases and Malaria, Center for Global Health, Centers for Disease Control and Prevention, Atlanta, GA 30333, USA Epidemic Intelligence Service, Centers for Disease Control and Prevention, Atlanta, GA 30333, USA
| | - Julie Gutman
- Malaria Branch, Division of Parasitic Diseases and Malaria, Center for Global Health, Centers for Disease Control and Prevention, Atlanta, GA 30333, USA
| | - Peter Lyaruu
- Ifakara Health Institute, Dar es Salaam, Tanzania
| | - S Patrick Kachur
- Malaria Branch, Division of Parasitic Diseases and Malaria, Center for Global Health, Centers for Disease Control and Prevention, Atlanta, GA 30333, USA
| | | | - Venkatachalam Udhayakumar
- Malaria Branch, Division of Parasitic Diseases and Malaria, Center for Global Health, Centers for Disease Control and Prevention, Atlanta, GA 30333, USA
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108
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Jansen PA, Grøntvedt RN, Tarpai A, Helgesen KO, Horsberg TE. Surveillance of the Sensitivity towards Antiparasitic Bath-Treatments in the Salmon Louse (Lepeophtheirus salmonis). PLoS One 2016; 11:e0149006. [PMID: 26889677 PMCID: PMC4759459 DOI: 10.1371/journal.pone.0149006] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2015] [Accepted: 01/26/2016] [Indexed: 11/18/2022] Open
Abstract
The evolution of drug resistant parasitic sea lice is of major concern to the salmon farming industry worldwide and challenges sustainable growth of this enterprise. To assess current status and development of L. salmonis sensitivity towards different pesticides used for parasite control in Norwegian salmon farming, a national surveillance programme was implemented in 2013. The programme aims to summarize data on the use of different pesticides applied to control L. salmonis and to test L. salmonis sensitivity to different pesticides in farms along the Norwegian coast. Here we analyse two years of test-data from biological assays designed to detect sensitivity-levels towards the pesticides azamethiphos and deltamethrin, both among the most common pesticides used in bath-treatments of farmed salmon in Norway in later years. The focus of the analysis is on how different variables predict the binomial outcome of the bioassay tests, being whether L. salmonis are immobilized/die or survive pesticide exposure. We found that local kernel densities of bath treatments, along with a spatial geographic index of test-farm locations, were significant predictors of the binomial outcome of the tests. Furthermore, the probability of L. salmonis being immobilized/dead after test-exposure was reduced by odds-ratios of 0.60 (95% CI: 0.42–0.86) for 2014 compared to 2013 and 0.39 (95% CI: 0.36–0.42) for low concentration compared to high concentration exposure. There were also significant but more marginal effects of parasite gender and developmental stage, and a relatively large random effect of test-farm. We conclude that the present data support an association between local intensities of bath treatments along the coast and the outcome of bioassay tests where salmon lice are exposed to azamethiphos or deltamethrin. Furthermore, there is a predictable structure of L. salmonis phenotypes along the coast in the data, characterized by high susceptibility to pesticides in the far north and far south, but low susceptibility in mid Norway. The study emphasizes the need to address local susceptibility to pesticides and the need for restrictive use of pesticides to preserve treatment efficacy.
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Affiliation(s)
- Peder A. Jansen
- Norwegian Veterinary Institute, Oslo, Norway
- Sea Lice Research Centre, Department of Biology, University of Bergen, Bergen, Norway
- * E-mail:
| | | | | | - Kari O. Helgesen
- NMBU School of Veterinary Science, Sea Lice Research Centre, Oslo, Norway
| | - Tor Einar Horsberg
- NMBU School of Veterinary Science, Sea Lice Research Centre, Oslo, Norway
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109
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Chindelevitch L, Colijn C, Moodley P, Wilson D, Cohen T. ClassTR: Classifying Within-Host Heterogeneity Based on Tandem Repeats with Application to Mycobacterium tuberculosis Infections. PLoS Comput Biol 2016; 12:e1004475. [PMID: 26829497 PMCID: PMC4734664 DOI: 10.1371/journal.pcbi.1004475] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2015] [Accepted: 07/22/2015] [Indexed: 11/18/2022] Open
Abstract
Genomic tools have revealed genetically diverse pathogens within some hosts. Within-host pathogen diversity, which we refer to as "complex infection", is increasingly recognized as a determinant of treatment outcome for infections like tuberculosis. Complex infection arises through two mechanisms: within-host mutation (which results in clonal heterogeneity) and reinfection (which results in mixed infections). Estimates of the frequency of within-host mutation and reinfection in populations are critical for understanding the natural history of disease. These estimates influence projections of disease trends and effects of interventions. The genotyping technique MLVA (multiple loci variable-number tandem repeats analysis) can identify complex infections, but the current method to distinguish clonal heterogeneity from mixed infections is based on a rather simple rule. Here we describe ClassTR, a method which leverages MLVA information from isolates collected in a population to distinguish mixed infections from clonal heterogeneity. We formulate the resolution of complex infections into their constituent strains as an optimization problem, and show its NP-completeness. We solve it efficiently by using mixed integer linear programming and graph decomposition. Once the complex infections are resolved into their constituent strains, ClassTR probabilistically classifies isolates as clonally heterogeneous or mixed by using a model of tandem repeat evolution. We first compare ClassTR with the standard rule-based classification on 100 simulated datasets. ClassTR outperforms the standard method, improving classification accuracy from 48% to 80%. We then apply ClassTR to a sample of 436 strains collected from tuberculosis patients in a South African community, of which 92 had complex infections. We find that ClassTR assigns an alternate classification to 18 of the 92 complex infections, suggesting important differences in practice. By explicitly modeling tandem repeat evolution, ClassTR helps to improve our understanding of the mechanisms driving within-host diversity of pathogens like Mycobacterium tuberculosis.
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Affiliation(s)
- Leonid Chindelevitch
- Department of Epidemiology of Microbial Diseases, Yale School of Public Health, New Haven, Connecticut, United States of America
- * E-mail:
| | - Caroline Colijn
- Department of Mathematics, Imperial College, London, United Kingdom
| | - Prashini Moodley
- School of Laboratory Medicine and Medical Sciences, Nelson R Mandela School of Medicine, University of KwaZulu-Natal, Durban, South Africa
| | - Douglas Wilson
- Department of Medicine, Edendale Hospital, Pietermaritzberg, South Africa
- Nelson R Mandela School of Medicine, University of KwaZulu-Natal, Durban, South Africa
| | - Ted Cohen
- Department of Epidemiology of Microbial Diseases, Yale School of Public Health, New Haven, Connecticut, United States of America
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110
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Day T, Read AF. Does High-Dose Antimicrobial Chemotherapy Prevent the Evolution of Resistance? PLoS Comput Biol 2016; 12:e1004689. [PMID: 26820986 PMCID: PMC4731197 DOI: 10.1371/journal.pcbi.1004689] [Citation(s) in RCA: 101] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2015] [Accepted: 11/30/2015] [Indexed: 12/25/2022] Open
Abstract
High-dose chemotherapy has long been advocated as a means of controlling drug resistance in infectious diseases but recent empirical studies have begun to challenge this view. We develop a very general framework for modeling and understanding resistance emergence based on principles from evolutionary biology. We use this framework to show how high-dose chemotherapy engenders opposing evolutionary processes involving the mutational input of resistant strains and their release from ecological competition. Whether such therapy provides the best approach for controlling resistance therefore depends on the relative strengths of these processes. These opposing processes typically lead to a unimodal relationship between drug pressure and resistance emergence. As a result, the optimal drug dose lies at either end of the therapeutic window of clinically acceptable concentrations. We illustrate our findings with a simple model that shows how a seemingly minor change in parameter values can alter the outcome from one where high-dose chemotherapy is optimal to one where using the smallest clinically effective dose is best. A review of the available empirical evidence provides broad support for these general conclusions. Our analysis opens up treatment options not currently considered as resistance management strategies, and it also simplifies the experiments required to determine the drug doses which best retard resistance emergence in patients. The evolution of antimicrobial resistant pathogens threatens much of modern medicine. For over one hundred years, the advice has been to ‘hit hard’, in the belief that high doses of antimicrobials best contain resistance evolution. We argue that nothing in evolutionary theory supports this as a good rule of thumb in the situations that challenge medicine. We show instead that the only generality is to either use the highest tolerable drug dose or the lowest clinically effective dose; that is, one of the two edges of the therapeutic window. This approach suggests treatment options not currently considered, and simplifies the experiments required to identify the dose that best retards resistance evolution.
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Affiliation(s)
- Troy Day
- Department of Mathematics and Statistics, Jeffery Hall, Queen’s University, Kingston, Ontario, Canada
- Department of Biology, Queen’s University, Kingston, Ontario, Canada
- The Fogarty International Center, National Institutes of Health, Bethesda, Maryland, United States of America
- * E-mail:
| | - Andrew F. Read
- The Fogarty International Center, National Institutes of Health, Bethesda, Maryland, United States of America
- Center for Infectious Disease Dynamics, Departments of Biology and Entomology, The Pennsylvania State University, University Park, Pennsylvania, United States of America
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111
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Ogbunugafor CB, Wylie CS, Diakite I, Weinreich DM, Hartl DL. Adaptive Landscape by Environment Interactions Dictate Evolutionary Dynamics in Models of Drug Resistance. PLoS Comput Biol 2016; 12:e1004710. [PMID: 26808374 PMCID: PMC4726534 DOI: 10.1371/journal.pcbi.1004710] [Citation(s) in RCA: 49] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2015] [Accepted: 12/16/2015] [Indexed: 12/12/2022] Open
Abstract
The adaptive landscape analogy has found practical use in recent years, as many have explored how their understanding can inform therapeutic strategies that subvert the evolution of drug resistance. A major barrier to applications of these concepts is a lack of detail concerning how the environment affects adaptive landscape topography, and consequently, the outcome of drug treatment. Here we combine empirical data, evolutionary theory, and computer simulations towards dissecting adaptive landscape by environment interactions for the evolution of drug resistance in two dimensions-drug concentration and drug type. We do so by studying the resistance mediated by Plasmodium falciparum dihydrofolate reductase (DHFR) to two related inhibitors-pyrimethamine and cycloguanil-across a breadth of drug concentrations. We first examine whether the adaptive landscapes for the two drugs are consistent with common definitions of cross-resistance. We then reconstruct all accessible pathways across the landscape, observing how their structure changes with drug environment. We offer a mechanism for non-linearity in the topography of accessible pathways by calculating of the interaction between mutation effects and drug environment, which reveals rampant patterns of epistasis. We then simulate evolution in several different drug environments to observe how these individual mutation effects (and patterns of epistasis) influence paths taken at evolutionary "forks in the road" that dictate adaptive dynamics in silico. In doing so, we reveal how classic metrics like the IC50 and minimal inhibitory concentration (MIC) are dubious proxies for understanding how evolution will occur across drug environments. We also consider how the findings reveal ambiguities in the cross-resistance concept, as subtle differences in adaptive landscape topography between otherwise equivalent drugs can drive drastically different evolutionary outcomes. Summarizing, we discuss the results with regards to their basic contribution to the study of empirical adaptive landscapes, and in terms of how they inform new models for the evolution of drug resistance.
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Affiliation(s)
- C. Brandon Ogbunugafor
- Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, Massachusetts, United States of America
- Broad Institute of MIT and Harvard, Cambridge, Massachusetts, United States of America
- * E-mail:
| | - C. Scott Wylie
- Department of Ecology and Evolutionary Biology, Brown University, Providence, Rhode Island, United States of America
| | - Ibrahim Diakite
- Department of Global Health and Social Medicine, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Daniel M. Weinreich
- Department of Ecology and Evolutionary Biology, Brown University, Providence, Rhode Island, United States of America
| | - Daniel L. Hartl
- Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, Massachusetts, United States of America
- Broad Institute of MIT and Harvard, Cambridge, Massachusetts, United States of America
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112
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Ogbunugafor CB, Hartl D. A pivot mutation impedes reverse evolution across an adaptive landscape for drug resistance in Plasmodium vivax. Malar J 2016; 15:40. [PMID: 26809718 PMCID: PMC4727274 DOI: 10.1186/s12936-016-1090-3] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2015] [Accepted: 01/10/2016] [Indexed: 12/03/2022] Open
Abstract
BACKGROUND The study of reverse evolution from resistant to susceptible phenotypes can reveal constraints on biological evolution, a topic for which evolutionary theory has relatively few general principles. The public health catastrophe of antimicrobial resistance in malaria has brought these constraints on evolution into a practical realm, with one proposed solution: withdrawing anti-malarial medication use in high resistance settings, built on the assumption that reverse evolution occurs readily enough that populations of pathogens may revert to their susceptible states. While past studies have suggested limits to reverse evolution, there have been few attempts to properly dissect its mechanistic constraints. METHODS Growth rates were determined from empirical data on the growth and resistance from a set of combinatorially complete set of mutants of a resistance protein (dihydrofolate reductase) in Plasmodium vivax, to construct reverse evolution trajectories. The fitness effects of individual mutations were calculated as a function of drug environment, revealing the magnitude of epistatic interactions between mutations and genetic backgrounds. Evolution across the landscape was simulated in two settings: starting from the population fixed for the quadruple mutant, and from a polymorphic population evenly distributed between double mutants. RESULTS A single mutation of large effect (S117N) serves as a pivot point for evolution to high resistance regions of the landscape. Through epistatic interactions with other mutations, this pivot creates an epistatic ratchet against reverse evolution towards the wild type ancestor, even in environments where the wild type is the most fit of all genotypes. This pivot mutation underlies the directional bias in evolution across the landscape, where evolution towards the ancestor is precluded across all examined drug concentrations from various starting points in the landscape. CONCLUSIONS The presence of pivot mutations can dictate dynamics of evolution across adaptive landscape through epistatic interactions within a protein, leaving a population trapped on local fitness peaks in an adaptive landscape, unable to locate ancestral genotypes. This irreversibility suggests that the structure of an adaptive landscape for a resistance protein should be understood before considering resistance management strategies. This proposed mechanism for constraints on reverse evolution corroborates evidence from the field indicating that phenotypic reversal often occurs via compensatory mutation at sites independent of those associated with the forward evolution of resistance. Because of this, molecular methods that identify resistance patterns via single SNPs in resistance-associated markers might be missing signals for resistance and compensatory mutation throughout the genome. In these settings, whole genome sequencing efforts should be used to identify resistance patterns, and will likely reveal a more complicated genomic signature for resistance and susceptibility, especially in settings where anti-malarial medications have been used intermittently. Lastly, the findings suggest that, given their role in dictating the dynamics of evolution across the landscape, pivot mutations might serve as future targets for therapy.
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Affiliation(s)
- C Brandon Ogbunugafor
- Department of Biology, University of Vermont, Burlington, VT, USA.
- Vermont Complex Systems Center, The University of Vermont, Burlington, VT, USA.
| | - Daniel Hartl
- Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA, USA.
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113
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Torres-Barceló C, Hochberg ME. Evolutionary Rationale for Phages as Complements of Antibiotics. Trends Microbiol 2016; 24:249-256. [PMID: 26786863 DOI: 10.1016/j.tim.2015.12.011] [Citation(s) in RCA: 180] [Impact Index Per Article: 22.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2015] [Revised: 12/15/2015] [Accepted: 12/28/2015] [Indexed: 01/21/2023]
Abstract
Antibiotic-resistant bacterial infections are a major concern to public health. Phage therapy has been proposed as a promising alternative to antibiotics, but an increasing number of studies suggest that both of these antimicrobial agents in combination are more effective in controlling pathogenic bacteria than either alone. We advocate the use of phages in combination with antibiotics and present the evolutionary basis for our claim. In addition, we identify compelling challenges for the realistic application of phage-antibiotic combined therapy.
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Affiliation(s)
- Clara Torres-Barceló
- Institut des Sciences de l'Evolution, Université Montpellier, Place E Bataillon 34095, Montpellier, France.
| | - Michael E Hochberg
- Institut des Sciences de l'Evolution, Université Montpellier, Place E Bataillon 34095, Montpellier, France; Santa Fe Institute, 1399 Hyde Park Road, Santa Fe, NM 87501, USA.
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114
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Leftwich PT, Bolton M, Chapman T. Evolutionary biology and genetic techniques for insect control. Evol Appl 2016; 9:212-30. [PMID: 27087849 PMCID: PMC4780389 DOI: 10.1111/eva.12280] [Citation(s) in RCA: 65] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2015] [Accepted: 05/25/2015] [Indexed: 01/15/2023] Open
Abstract
The requirement to develop new techniques for insect control that minimize negative environmental impacts has never been more pressing. Here we discuss population suppression and population replacement technologies. These include sterile insect technique, genetic elimination methods such as the release of insects carrying a dominant lethal (RIDL), and gene driving mechanisms offered by intracellular bacteria and homing endonucleases. We also review the potential of newer or underutilized methods such as reproductive interference, CRISPR technology, RNA interference (RNAi), and genetic underdominance. We focus on understanding principles and potential effectiveness from the perspective of evolutionary biology. This offers useful insights into mechanisms through which potential problems may be minimized, in much the same way that an understanding of how resistance evolves is key to slowing the spread of antibiotic and insecticide resistance. We conclude that there is much to gain from applying principles from the study of resistance in these other scenarios - specifically, the adoption of combinatorial approaches to minimize the spread of resistance evolution. We conclude by discussing the focused use of GM for insect pest control in the context of modern conservation planning under land-sparing scenarios.
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Affiliation(s)
- Philip T. Leftwich
- School of Biological SciencesUniversity of East AngliaNorwich Research ParkNorwichUK
| | - Michael Bolton
- School of Biological SciencesUniversity of East AngliaNorwich Research ParkNorwichUK
| | - Tracey Chapman
- School of Biological SciencesUniversity of East AngliaNorwich Research ParkNorwichUK
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115
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Wang X, Zhang J, Wang Y, Wang C, Xiao J, Zhang Q, Cheng Y. Multi-responsive photothermal-chemotherapy with drug-loaded melanin-like nanoparticles for synergetic tumor ablation. Biomaterials 2015; 81:114-124. [PMID: 26731575 DOI: 10.1016/j.biomaterials.2015.11.037] [Citation(s) in RCA: 299] [Impact Index Per Article: 33.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2015] [Accepted: 11/29/2015] [Indexed: 12/11/2022]
Abstract
Photothermal-chemotherapy (PT-CT) is a promising strategy for cancer treatment, but its development is hindered by the issues regarding to the long-term safety of carriers and imperfect drug release profiles. In this article, we use polyethylene glycol-modified polydopamine nanoparticles (PDA-PEG) as an outstanding PT-CT agent for cancer treatment. PDA-PEG possesses excellent biocompatibility and photothermal effect, and could easily load anticancer drugs such as doxorubicin (DOX) and 7-ethyl-10-hydroxycamptothecin (SN38) via π-π stacking and/or hydrogen binding. Moreover, the drug-loaded PDA-PEG showed great stability and drug-retaining capability in physiological condition, and could respond to multiple stimuli including near infrared light, pH and reactive oxygen species to trigger the release of loaded anticancer drugs. The in vitro and in vivo studies demonstrated that PDA-PEG-mediated PT-CT showed synergetic effect for cancer therapy.
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Affiliation(s)
- Xinyu Wang
- Shanghai Key Laboratory of Regulatory Biology, School of Life Sciences, East China Normal University, Shanghai, 200241, PR China
| | - Jishen Zhang
- Department of Orthopedic Oncology, Changzheng Hospital, The Second Military Medical University, Shanghai, 200003, PR China
| | - Yitong Wang
- Shanghai Key Laboratory of Regulatory Biology, School of Life Sciences, East China Normal University, Shanghai, 200241, PR China
| | - Changping Wang
- Shanghai Key Laboratory of Regulatory Biology, School of Life Sciences, East China Normal University, Shanghai, 200241, PR China
| | - Jianru Xiao
- Department of Orthopedic Oncology, Changzheng Hospital, The Second Military Medical University, Shanghai, 200003, PR China.
| | - Qiang Zhang
- Shanghai Key Laboratory of Regulatory Biology, School of Life Sciences, East China Normal University, Shanghai, 200241, PR China.
| | - Yiyun Cheng
- Shanghai Key Laboratory of Regulatory Biology, School of Life Sciences, East China Normal University, Shanghai, 200241, PR China.
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116
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The Role of Recombination in Evolutionary Rescue. Genetics 2015; 202:721-32. [PMID: 26627842 DOI: 10.1534/genetics.115.180299] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2015] [Accepted: 11/16/2015] [Indexed: 11/18/2022] Open
Abstract
How likely is it that a population escapes extinction through adaptive evolution? The answer to this question is of great relevance in conservation biology, where we aim at species' rescue and the maintenance of biodiversity, and in agriculture and medicine, where we seek to hamper the emergence of pesticide or drug resistance. By reshuffling the genome, recombination has two antagonistic effects on the probability of evolutionary rescue: it generates and it breaks up favorable gene combinations. Which of the two effects prevails depends on the fitness effects of mutations and on the impact of stochasticity on the allele frequencies. In this article, we analyze a mathematical model for rescue after a sudden environmental change when adaptation is contingent on mutations at two loci. The analysis reveals a complex nonlinear dependence of population survival on recombination. We moreover find that, counterintuitively, a fast eradication of the wild type can promote rescue in the presence of recombination. The model also shows that two-step rescue is not unlikely to happen and can even be more likely than single-step rescue (where adaptation relies on a single mutation), depending on the circumstances.
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117
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Extremely high genetic diversity in a single tumor points to prevalence of non-Darwinian cell evolution. Proc Natl Acad Sci U S A 2015; 112:E6496-505. [PMID: 26561581 DOI: 10.1073/pnas.1519556112] [Citation(s) in RCA: 234] [Impact Index Per Article: 26.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
The prevailing view that the evolution of cells in a tumor is driven by Darwinian selection has never been rigorously tested. Because selection greatly affects the level of intratumor genetic diversity, it is important to assess whether intratumor evolution follows the Darwinian or the non-Darwinian mode of evolution. To provide the statistical power, many regions in a single tumor need to be sampled and analyzed much more extensively than has been attempted in previous intratumor studies. Here, from a hepatocellular carcinoma (HCC) tumor, we evaluated multiregional samples from the tumor, using either whole-exome sequencing (WES) (n = 23 samples) or genotyping (n = 286) under both the infinite-site and infinite-allele models of population genetics. In addition to the many single-nucleotide variations (SNVs) present in all samples, there were 35 "polymorphic" SNVs among samples. High genetic diversity was evident as the 23 WES samples defined 20 unique cell clones. With all 286 samples genotyped, clonal diversity agreed well with the non-Darwinian model with no evidence of positive Darwinian selection. Under the non-Darwinian model, MALL (the number of coding region mutations in the entire tumor) was estimated to be greater than 100 million in this tumor. DNA sequences reveal local diversities in small patches of cells and validate the estimation. In contrast, the genetic diversity under a Darwinian model would generally be orders of magnitude smaller. Because the level of genetic diversity will have implications on therapeutic resistance, non-Darwinian evolution should be heeded in cancer treatments even for microscopic tumors.
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118
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Vestergaard M, Paulander W, Marvig RL, Clasen J, Jochumsen N, Molin S, Jelsbak L, Ingmer H, Folkesson A. Antibiotic combination therapy can select for broad-spectrum multidrug resistance in Pseudomonas aeruginosa. Int J Antimicrob Agents 2015; 47:48-55. [PMID: 26597931 DOI: 10.1016/j.ijantimicag.2015.09.014] [Citation(s) in RCA: 59] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2015] [Revised: 09/14/2015] [Accepted: 09/29/2015] [Indexed: 12/26/2022]
Abstract
Combination therapy with several antibiotics is one strategy that has been applied in order to limit the spread of antimicrobial resistance. We compared the de novo evolution of resistance during combination therapy with the β-lactam ceftazidime and the fluoroquinolone ciprofloxacin with the resistance evolved after single-drug exposure. Combination therapy selected for mutants that displayed broad-spectrum resistance, and a major resistance mechanism was mutational inactivation of the repressor gene mexR that regulates the multidrug efflux operon mexAB-oprM. Deregulation of this operon led to a broad-spectrum resistance phenotype that decreased susceptibility to the combination of drugs applied during selection as well as to unrelated antibiotic classes. Mutants isolated after single-drug exposure displayed narrow-spectrum resistance and carried mutations in the MexCD-OprJ efflux pump regulator gene nfxB conferring ciprofloxacin resistance, or in the gene encoding the non-essential penicillin-binding protein DacB conferring ceftazidime resistance. Reconstruction of resistance mutations by allelic replacement and in vitro fitness assays revealed that in contrast to single antibiotic use, combination therapy consistently selected for mutants with enhanced fitness expressing broad-spectrum resistance mechanisms.
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Affiliation(s)
- Martin Vestergaard
- Department of Veterinary Disease Biology, University of Copenhagen, Copenhagen, Denmark
| | - Wilhelm Paulander
- Department of Veterinary Disease Biology, University of Copenhagen, Copenhagen, Denmark
| | - Rasmus L Marvig
- Center for Genomic Medicine, Rigshospitalet, Copenhagen, Denmark
| | - Julie Clasen
- National Veterinary Institute, Technical University of Denmark, Copenhagen, Denmark
| | - Nicholas Jochumsen
- Department of Systems Biology, Technical University of Denmark, Copenhagen, Denmark
| | - Søren Molin
- Department of Systems Biology, Technical University of Denmark, Copenhagen, Denmark
| | - Lars Jelsbak
- Department of Systems Biology, Technical University of Denmark, Copenhagen, Denmark
| | - Hanne Ingmer
- Department of Veterinary Disease Biology, University of Copenhagen, Copenhagen, Denmark
| | - Anders Folkesson
- National Veterinary Institute, Technical University of Denmark, Copenhagen, Denmark.
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119
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Woods RJ, Read AF. Clinical management of resistance evolution in a bacterial infection: A case study. EVOLUTION MEDICINE AND PUBLIC HEALTH 2015; 2015:281-8. [PMID: 26454762 PMCID: PMC4629395 DOI: 10.1093/emph/eov025] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/09/2015] [Accepted: 09/17/2015] [Indexed: 11/24/2022]
Abstract
This chronic bacterial infection evolved extensive resistance, killing the patient. Evolutionary science is insufficiently developed to better manage such life-threatening evolution. We report the case of a patient with a chronic bacterial infection that could not be cured. Drug treatment became progressively less effective due to antibiotic resistance, and the patient died, in effect from overwhelming evolution. Even though the evolution of drug resistance was recognized as a major threat, and the fundamentals of drug resistance evolution are well understood, it was impossible to make evidence-based decisions about the evolutionary risks associated with the various treatment options. We present this case to illustrate the urgent need for translational research in the evolutionary medicine of antibiotic resistance.
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Affiliation(s)
- Robert J Woods
- Division of Infectious Diseases, Department of Internal Medicine, University of Michigan, Ann Arbor, MI 48109, USA
| | - Andrew F Read
- Department of Biology, Center for Infectious Disease Dynamics, Pennsylvania State University, University Park PA 16802, USA Department of Entomology, Center for Infectious Disease Dynamics, Pennsylvania State University, University Park PA 16802, USA
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120
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Colijn C, Cohen T. How competition governs whether moderate or aggressive treatment minimizes antibiotic resistance. eLife 2015; 4. [PMID: 26393685 PMCID: PMC4641510 DOI: 10.7554/elife.10559] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2015] [Accepted: 09/18/2015] [Indexed: 11/16/2022] Open
Abstract
Understanding how our use of antimicrobial drugs shapes future levels of drug resistance is crucial. Recently, there has been debate over whether an aggressive (i.e., high dose) or more moderate (i.e., lower dose) treatment of individuals will most limit the emergence and spread of resistant bacteria. In this study, we demonstrate how one can understand and resolve these apparently contradictory conclusions. We show that a key determinant of which treatment strategy will perform best at the individual level is the extent of effective competition between resistant and sensitive pathogens within a host. We extend our analysis to the community level, exploring the spectrum between strict inter-strain competition and strain independence. From this perspective as well, we find that the magnitude of effective competition between resistant and sensitive strains determines whether an aggressive approach or moderate approach minimizes the burden of resistance in the population. DOI:http://dx.doi.org/10.7554/eLife.10559.001 Antibiotics are chemical compounds used to treat bacterial infections. The discovery of antibiotics, starting with penicillin in 1929, revolutionized medicine, making it possible to cure or prevent life-threatening infections such as tetanus and pneumonia. However, many bacteria have become resistant to one or more antibiotics and so can no longer be killed by these drugs. The emergence of antibiotic resistance reflects an evolutionary process that occurs during antibiotic treatment. While the antibiotic will kill most bacteria, some bacteria may naturally have a feature or genetic mutation that allows them to survive in the presence of the antibiotic. These bacteria then reproduce and pass on their resistant traits, eventually leading to the emergence of a new antibiotic-resistant strain of bacteria. Once a resistant strain exists it may be able to spread from one person to another. There is conflicting evidence about how best to prevent antibiotic-resistant bacteria from evolving and spreading. The results of some experiments suggest that treating bacteria with large doses of antibiotics early in an infection is the most effective way to optimize treatment and minimize the risk of an antibiotic-resistant strain developing. However, other studies suggest that exposing bacteria to high levels of antibiotics more efficiently selects for resistance; in this case a more moderate approach should be used when treating bacterial infections. Here, Colijn and Cohen present a mathematical model that suggests that the natural competition between the antibiotic-resistant and antibiotic-sensitive strains of bacteria influence which treatment strategy should be taken. Strains were modeled both within individual hosts and spreading in a community of individuals. In the models, aggressive antibiotic treatment is most effective (in that it minimizes antibiotic resistance) when the antibiotic-resistant strain either does not experience strong competition from the non-resistant strains of bacteria or is not fit enough to be a good competitor. However, a more moderate treatment is appropriate when the two strains are competing and the antibiotic-resistant strain is a fit competitor. Competition may mean that moderate treatment is best to avoid resistance at the community level, even in situations when aggressive treatment is likely best for individuals. Two important future challenges are to better understand the diversity of strains in bacterial infections, and to develop tools to measure to what extent strains are effectively competing with each other. DOI:http://dx.doi.org/10.7554/eLife.10559.002
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Affiliation(s)
- Caroline Colijn
- Department of Mathematics, Imperial College London, London, United Kingdom
| | - Ted Cohen
- School of Public Health, Yale University, New Haven, United States
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121
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Moura de Sousa J, Sousa A, Bourgard C, Gordo I. Potential for adaptation overrides cost of resistance. Future Microbiol 2015; 10:1415-31. [PMID: 26343510 DOI: 10.2217/fmb.15.61] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
AIM To investigate the cost of antibiotic resistance versus the potential for resistant clones to adapt in maintaining polymorphism for resistance. MATERIALS & METHODS Experimental evolution of Escherichia coli carrying different resistance alleles was performed under an environment devoid of antibiotics and evolutionary parameters estimated from their frequencies along time. RESULTS & CONCLUSION Costly resistance mutations were found to coexist with lower cost resistances for hundreds of generations, contrary to the hypothesis that the cost of a resistance dictates its extinction. Estimated evolutionary parameters for the different resistance backgrounds suggest a higher adaptive potential of clones with costly antibiotic resistance mutations, overriding their initial cost of resistance and allowing their maintenance in the absence of drugs.
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Affiliation(s)
| | - Ana Sousa
- Instituto Gulbenkian de Ciência, Rua da Quinta Grande 6, Oeiras, Portugal
| | - Catarina Bourgard
- Instituto Gulbenkian de Ciência, Rua da Quinta Grande 6, Oeiras, Portugal
| | - Isabel Gordo
- Instituto Gulbenkian de Ciência, Rua da Quinta Grande 6, Oeiras, Portugal
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122
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Do mixed infections matter? Assessing virulence of mixed-clone infections in experimental human and murine malaria. INFECTION GENETICS AND EVOLUTION 2015; 36:82-91. [PMID: 26334940 DOI: 10.1016/j.meegid.2015.08.041] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/30/2015] [Revised: 08/27/2015] [Accepted: 08/27/2015] [Indexed: 01/26/2023]
Abstract
BACKGROUND Malaria parasites within an individual infection often consist of multiple strains (clonal populations) of a single species, which have the potential to interact both with one another, and with the host immune system. Several effects of these interactions have been measured in different parasite systems including competition and mutualism; however, direct observation of these effects in human malaria has been limited by sampling complexities and inherent ethical limitations. METHODS Using multiple complementary epidemiological models, we propose a suite of analyses to more fully utilize data from challenge experiments, and re-examine historical human challenge studies with mixed-strain Plasmodium vivax inocula. We then compare these results with murine model systems using mixed-strain Plasmodium yoelii or Plasmodium chabaudi, to explore the utility of these methods in fully utilizing these data, including the first quantitative estimates of effect sizes for mixed-strain parasitemia. These models also provide a method to assess consistency within these animal model systems. RESULTS We find that amongst a limited set of P. vivax (incubation time) and P. yoelii infections (time-to-mortality), survival times at a study population-level are intermediate between each single-clone infection, and are not dominated by the more virulent clone; in P. vivax relapses, mixed clone infections also show intermediate survival curves. In these infections, the results strongly suggest that highly virulent clones have their virulence attenuated by the presence of less-virulent clones. The analysis of multiple experiments with P. chabaudi suggests greater nuances in the interactions between strains, and that mortality and time-to-event in mixed-strain infections are both indistinguishable from single infections with the more virulent strain. CONCLUSIONS These divergent dynamics support earlier work that suggested drivers of virulence may differ in fundamental ways between malaria species that are reticulocyte-specific and those that readily infect all red blood cell stages which should be studied in greater detail. The effect sizes (magnitude of biological effects) from these analyses are significant, and suggest the potential for important gains in malaria control by greater incorporation of evolutionary epidemiology theory. Moreover, we suggest that using these epidemiological models may generally allow fuller use of data from experimentally challenging animal model experiments.
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123
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Pollitt LC, Bram JT, Blanford S, Jones MJ, Read AF. Existing Infection Facilitates Establishment and Density of Malaria Parasites in Their Mosquito Vector. PLoS Pathog 2015; 11:e1005003. [PMID: 26181518 PMCID: PMC4504473 DOI: 10.1371/journal.ppat.1005003] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2015] [Accepted: 06/04/2015] [Indexed: 02/06/2023] Open
Abstract
Very little is known about how vector-borne pathogens interact within their vector and how this impacts transmission. Here we show that mosquitoes can accumulate mixed strain malaria infections after feeding on multiple hosts. We found that parasites have a greater chance of establishing and reach higher densities if another strain is already present in a mosquito. Mixed infections contained more parasites but these larger populations did not have a detectable impact on vector survival. Together these results suggest that mosquitoes taking multiple infective bites may disproportionally contribute to malaria transmission. This will increase rates of mixed infections in vertebrate hosts, with implications for the evolution of parasite virulence and the spread of drug-resistant strains. Moreover, control measures that reduce parasite prevalence in vertebrate hosts will reduce the likelihood of mosquitoes taking multiple infective feeds, and thus disproportionally reduce transmission. More generally, our study shows that the types of strain interactions detected in vertebrate hosts cannot necessarily be extrapolated to vectors.
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Affiliation(s)
- Laura C. Pollitt
- Centre for Immunity, Infection and Evolution, University of Edinburgh, Edinburgh, United Kingdom
- Center for Infectious Disease Dynamics, Departments of Biology and Entomology, Pennsylvania State University, State College, Pennsylvania, United States of America
- * E-mail:
| | - Joshua T. Bram
- Center for Infectious Disease Dynamics, Departments of Biology and Entomology, Pennsylvania State University, State College, Pennsylvania, United States of America
| | - Simon Blanford
- Center for Infectious Disease Dynamics, Departments of Biology and Entomology, Pennsylvania State University, State College, Pennsylvania, United States of America
| | - Matthew J. Jones
- Center for Infectious Disease Dynamics, Departments of Biology and Entomology, Pennsylvania State University, State College, Pennsylvania, United States of America
| | - Andrew F. Read
- Center for Infectious Disease Dynamics, Departments of Biology and Entomology, Pennsylvania State University, State College, Pennsylvania, United States of America
- Fogarty International Center, National Institutes of Health, Bethesda, Maryland, United States of America
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124
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McClure NS, Day T. A theoretical examination of the relative importance of evolution management and drug development for managing resistance. Proc Biol Sci 2015; 281:rspb.2014.1861. [PMID: 25377456 PMCID: PMC4240990 DOI: 10.1098/rspb.2014.1861] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Drug resistance is a serious public health problem that threatens to thwart our ability to treat many infectious diseases. Repeatedly, the introduction of new drugs has been followed by the evolution of resistance. In principle, there are two complementary ways to address this problem: (i) enhancing drug development and (ii) slowing the evolution of drug resistance through evolutionary management. Although these two strategies are not mutually exclusive, it is nevertheless worthwhile considering whether one might be inherently more effective than the other. We present a simple mathematical model that explores how interventions aimed at these two approaches affect the availability of effective drugs. Our results identify an interesting feature of evolution management that, all else equal, tends to make it more effective than enhancing drug development. Thus, although enhancing drug development will necessarily be a central part of addressing the problem of resistance, our results lend support to the idea that evolution management is probably a very significant component of the solution as well.
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Affiliation(s)
- Nathan S McClure
- Department of Biology, Queen's University, Kingston, Ontario, Canada K7L 3N6
| | - Troy Day
- Department of Biology, Queen's University, Kingston, Ontario, Canada K7L 3N6 Department of Mathematics and Statistics, Queen's University, Kingston, Ontario, Canada K7L 3N6
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125
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Hao YQ, Brockhurst MA, Petchey OL, Zhang QG. Evolutionary rescue can be impeded by temporary environmental amelioration. Ecol Lett 2015; 18:892-8. [PMID: 26119065 DOI: 10.1111/ele.12465] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2015] [Revised: 03/13/2015] [Accepted: 05/20/2015] [Indexed: 02/04/2023]
Abstract
Rapid evolutionary adaptation has the potential to rescue from extinction populations experiencing environmental changes. Little is known, however, about the impact of short-term environmental fluctuations during long-term environmental deterioration, an intrinsic property of realistic environmental changes. Temporary environmental amelioration arising from such fluctuations could either facilitate evolutionary rescue by allowing population recovery (a positive demographic effect) or impede it by relaxing selection for beneficial mutations required for future survival (a negative population genetic effect). We address this uncertainty in an experiment with populations of a bacteriophage virus that evolved under deteriorating conditions (gradually increasing temperature). Periodic environmental amelioration (short periods of reduced temperature) caused demographic recovery during the early phase of the experiment, but ultimately reduced the frequency of evolutionary rescue. These experimental results suggest that environmental fluctuations could reduce the potential of evolutionary rescue.
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Affiliation(s)
- Yi-Qi Hao
- Institute for Evolutionary Biology and Environmental Studies, University of Zurich, Winterthurerstrasse 190, 8057, Zurich, Switzerland.,State Key Laboratory of Earth Surface Processes and Resource Ecology and MOE Key Laboratory for Biodiversity Science and Ecological Engineering, Beijing Normal University, Beijing, 100875, China
| | | | - Owen L Petchey
- Institute for Evolutionary Biology and Environmental Studies, University of Zurich, Winterthurerstrasse 190, 8057, Zurich, Switzerland.,Department of Aquatic Ecology, Eawag: Swiss Federal Institute of Aquatic Science and Technology, Dübendorf, Switzerland
| | - Quan-Guo Zhang
- State Key Laboratory of Earth Surface Processes and Resource Ecology and MOE Key Laboratory for Biodiversity Science and Ecological Engineering, Beijing Normal University, Beijing, 100875, China
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126
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Kouyos RD, Metcalf CJE, Birger R, Klein EY, Abel zur Wiesch P, Ankomah P, Arinaminpathy N, Bogich TL, Bonhoeffer S, Brower C, Chi-Johnston G, Cohen T, Day T, Greenhouse B, Huijben S, Metlay J, Mideo N, Pollitt LC, Read AF, Smith DL, Standley C, Wale N, Grenfell B. The path of least resistance: aggressive or moderate treatment? Proc Biol Sci 2015; 281:20140566. [PMID: 25253451 DOI: 10.1098/rspb.2014.0566] [Citation(s) in RCA: 62] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
The evolution of resistance to antimicrobial chemotherapy is a major and growing cause of human mortality and morbidity. Comparatively little attention has been paid to how different patient treatment strategies shape the evolution of resistance. In particular, it is not clear whether treating individual patients aggressively with high drug dosages and long treatment durations, or moderately with low dosages and short durations can better prevent the evolution and spread of drug resistance. Here, we summarize the very limited available empirical evidence across different pathogens and provide a conceptual framework describing the information required to effectively manage drug pressure to minimize resistance evolution.
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Affiliation(s)
- Roger D Kouyos
- Department of Ecology and Evolutionary Biology, Princeton University, Princeton, NJ, USA Division of Infectious Diseases and Hospital Epidemiology, University Hospital Zürich, University of Zürich, Zürich, Switzerland
| | - C Jessica E Metcalf
- Department of Ecology and Evolutionary Biology, Princeton University, Princeton, NJ, USA Department of Zoology, Oxford University, Oxford, UK
| | - Ruthie Birger
- Department of Ecology and Evolutionary Biology, Princeton University, Princeton, NJ, USA
| | - Eili Y Klein
- Department of Ecology and Evolutionary Biology, Princeton University, Princeton, NJ, USA Center for Advanced Modeling, Department of Emergency Medicine, Johns Hopkins University, Baltimore, MD, USA
| | - Pia Abel zur Wiesch
- Division of Global Health Equity, Brigham and Women's Hospital and Department of Epidemiology, Harvard School of Public Health, Boston, MA, USA
| | - Peter Ankomah
- Department of Biology, Emory University, Atlanta, GA, USA
| | - Nimalan Arinaminpathy
- Department of Ecology and Evolutionary Biology, Princeton University, Princeton, NJ, USA Department of Infectious Disease Epidemiology, Imperial College London, London, UK
| | - Tiffany L Bogich
- Department of Ecology and Evolutionary Biology, Princeton University, Princeton, NJ, USA Fogarty International Center, National Institutes of Health, Bethesda, MD, USA
| | | | - Charles Brower
- Department of Ecology and Evolutionary Biology, Princeton University, Princeton, NJ, USA Center for Disease Dynamics, Economics & Policy, Washington, DC, USA
| | - Geoffrey Chi-Johnston
- Department of Epidemiology, Bloomberg School of Public Health, Johns Hopkins University, Baltimore, MD, USA
| | - Ted Cohen
- Division of Global Health Equity, Brigham and Women's Hospital and Department of Epidemiology, Harvard School of Public Health, Boston, MA, USA
| | - Troy Day
- Departments of Mathematics and Biology, Queen's University, Kingston, Ontario, Canada
| | - Bryan Greenhouse
- Department of Medicine, Division of Infectious Diseases, University of California, San Francisco, VA, USA
| | - Silvie Huijben
- Barcelona Centre for International Health Research, Hospital Clínic, Universitat de Barcelona, Barcelona, Spain
| | - Joshua Metlay
- General Medicine Division, Massachusetts General Hospital, Boston, MA, USA
| | - Nicole Mideo
- Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, Ontario, Canada
| | - Laura C Pollitt
- Centre for Infectious Disease Dynamics, The Pennsylvania State University, University Park, State College, PA, USA Departments of Biology and Entomology, The Pennsylvania State University, University Park, State College, PA, USA Centre for Immunology, Infection and Evolution, University of Edinburgh, Edinburgh, UK
| | - Andrew F Read
- Centre for Infectious Disease Dynamics, The Pennsylvania State University, University Park, State College, PA, USA Departments of Biology and Entomology, The Pennsylvania State University, University Park, State College, PA, USA Fogarty International Center, National Institutes of Health, Bethesda, MD, USA
| | - David L Smith
- Department of Zoology, Oxford University, Oxford, UK
| | - Claire Standley
- Department of Health Policy, George Washington University, Washington, DC, USA
| | - Nina Wale
- Centre for Infectious Disease Dynamics, The Pennsylvania State University, University Park, State College, PA, USA Departments of Biology and Entomology, The Pennsylvania State University, University Park, State College, PA, USA
| | - Bryan Grenfell
- Department of Ecology and Evolutionary Biology, Princeton University, Princeton, NJ, USA Fogarty International Center, National Institutes of Health, Bethesda, MD, USA
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127
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Moreno-Gamez S, Hill AL, Rosenbloom DIS, Petrov DA, Nowak MA, Pennings PS. Imperfect drug penetration leads to spatial monotherapy and rapid evolution of multidrug resistance. Proc Natl Acad Sci U S A 2015; 112:E2874-83. [PMID: 26038564 PMCID: PMC4460514 DOI: 10.1073/pnas.1424184112] [Citation(s) in RCA: 96] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Infections with rapidly evolving pathogens are often treated using combinations of drugs with different mechanisms of action. One of the major goal of combination therapy is to reduce the risk of drug resistance emerging during a patient's treatment. Although this strategy generally has significant benefits over monotherapy, it may also select for multidrug-resistant strains, particularly during long-term treatment for chronic infections. Infections with these strains present an important clinical and public health problem. Complicating this issue, for many antimicrobial treatment regimes, individual drugs have imperfect penetration throughout the body, so there may be regions where only one drug reaches an effective concentration. Here we propose that mismatched drug coverage can greatly speed up the evolution of multidrug resistance by allowing mutations to accumulate in a stepwise fashion. We develop a mathematical model of within-host pathogen evolution under spatially heterogeneous drug coverage and demonstrate that even very small single-drug compartments lead to dramatically higher resistance risk. We find that it is often better to use drug combinations with matched penetration profiles, although there may be a trade-off between preventing eventual treatment failure due to resistance in this way and temporarily reducing pathogen levels systemically. Our results show that drugs with the most extensive distribution are likely to be the most vulnerable to resistance. We conclude that optimal combination treatments should be designed to prevent this spatial effective monotherapy. These results are widely applicable to diverse microbial infections including viruses, bacteria, and parasites.
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Affiliation(s)
- Stefany Moreno-Gamez
- Program for Evolutionary Dynamics, Department of Mathematics, Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA 02138; Theoretical Biology Group, Groningen Institute for Evolutionary Life Sciences, University of Groningen, Groningen, 9747 AG, The Netherlands
| | - Alison L Hill
- Program for Evolutionary Dynamics, Department of Mathematics, Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA 02138
| | - Daniel I S Rosenbloom
- Program for Evolutionary Dynamics, Department of Mathematics, Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA 02138; Department of Biomedical Informatics, Columbia University Medical Center, New York, NY 10032
| | - Dmitri A Petrov
- Department of Biology, Stanford University, Stanford, CA 94305
| | - Martin A Nowak
- Program for Evolutionary Dynamics, Department of Mathematics, Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA 02138
| | - Pleuni S Pennings
- Department of Biology, Stanford University, Stanford, CA 94305; Department of Biology, San Francisco State University, San Francisco, CA 94132; and Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA 02138
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128
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Opinion: Control vs. eradication: applying infectious disease treatment strategies to cancer. Proc Natl Acad Sci U S A 2015; 112:937-8. [PMID: 25628412 DOI: 10.1073/pnas.1420297111] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
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129
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Mbenda HGN, Awasthi G, Singh PK, Gouado I, Das A. Does malaria epidemiology project Cameroon as 'Africa in miniature'? J Biosci 2015; 39:727-38. [PMID: 25116627 DOI: 10.1007/s12038-014-9451-y] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Cameroon, a west-central African country with a ~ 20 million population, is commonly regarded as 'Africa in miniature' due to the extensive biological and cultural diversities of whole Africa being present in a single-country setting. This country is inhabited by ancestral human lineages in unique eco-climatic conditions and diverse topography. Over 90 percent Cameroonians are at risk of malaria infection, and ~ 41 percent have at least one episode of malaria each year. Historically, the rate of malaria infection in Cameroon has fluctuated over the years; the number of cases was about 2 million in 2010 and 2011. The Cameroonian malaria control programme faces an uphill task due to high prevalence of multidrug-resistant parasites and insecticide-resistant malaria vectors. Above all, continued human migration from the rural to urban areas as well as population exchange with adjoining countries, high rate of ecological instabilities caused by deforestation, poor housing, lack of proper sanitation and drainage system might have resulted in the recent increase in incidences of malaria and other vector-borne diseases in Cameroon. The available data on eco-environmental variability and intricate malaria epidemiology in Cameroon reflect the situation in the whole of Africa, and warrant the need for in-depth study by using modern surveillance tools for meaningful basic understanding of the malaria triangle (host-parasite-vector-environment).
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Affiliation(s)
- Huguette Gaelle Ngassa Mbenda
- Evolutionary Genomics and Bioinformatics Laboratory, Division of Genomics and Bioinformatics, National Institute of Malaria Research, New Delhi 110 077, India
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130
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Heesterbeek H, Anderson RM, Andreasen V, Bansal S, De Angelis D, Dye C, Eames KTD, Edmunds WJ, Frost SDW, Funk S, Hollingsworth TD, House T, Isham V, Klepac P, Lessler J, Lloyd-Smith JO, Metcalf CJE, Mollison D, Pellis L, Pulliam JRC, Roberts MG, Viboud C. Modeling infectious disease dynamics in the complex landscape of global health. Science 2015; 347:aaa4339. [PMID: 25766240 PMCID: PMC4445966 DOI: 10.1126/science.aaa4339] [Citation(s) in RCA: 346] [Impact Index Per Article: 38.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Despite some notable successes in the control of infectious diseases, transmissible pathogens still pose an enormous threat to human and animal health. The ecological and evolutionary dynamics of infections play out on a wide range of interconnected temporal, organizational, and spatial scales, which span hours to months, cells to ecosystems, and local to global spread. Moreover, some pathogens are directly transmitted between individuals of a single species, whereas others circulate among multiple hosts, need arthropod vectors, or can survive in environmental reservoirs. Many factors, including increasing antimicrobial resistance, increased human connectivity and changeable human behavior, elevate prevention and control from matters of national policy to international challenge. In the face of this complexity, mathematical models offer valuable tools for synthesizing information to understand epidemiological patterns, and for developing quantitative evidence for decision-making in global health.
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Affiliation(s)
- Hans Heesterbeek
- Faculty of Veterinary Medicine, University of Utrecht, Utrecht, Netherlands.
| | | | | | | | | | | | - Ken T D Eames
- Centre for the Mathematical Modelling of Infectious Diseases, London School of Hygiene Tropical Medicine, London, UK
| | - W John Edmunds
- Centre for the Mathematical Modelling of Infectious Diseases, London School of Hygiene Tropical Medicine, London, UK
| | | | | | - T Deirdre Hollingsworth
- School of Life Sciences, University of Warwick, UK. School of Tropical Medicine, University of Liverpool, UK
| | - Thomas House
- Warwick Mathematics Institute, University of Warwick, Coventry, UK
| | - Valerie Isham
- Department of Statistical Science, University College London, London, UK
| | | | - Justin Lessler
- Department of Epidemiology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA
| | - James O Lloyd-Smith
- Department of Ecology and Evolutionary Biology, University of California, Los Angeles, CA, USA
| | - C Jessica E Metcalf
- Department of Zoology, University of Oxford, Oxford, UK, and Department of Ecology and Evolutionary Biology, Princeton University, Princeton, NJ, USA
| | | | - Lorenzo Pellis
- Warwick Mathematics Institute, University of Warwick, Coventry, UK
| | - Juliet R C Pulliam
- Department of Biology-Emerging Pathogens Institute, University of Florida, Gainesville, FL, USA. Division of International Epidemiology and Population Studies, Fogarty International Center, NIH, Bethesda, MD, USA
| | - Mick G Roberts
- Institute of Natural and Mathematical Sciences, Massey University, Auckland, New Zealand
| | - Cecile Viboud
- Division of International Epidemiology and Population Studies, Fogarty International Center, NIH, Bethesda, MD, USA
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131
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Day T, Huijben S, Read AF. Is selection relevant in the evolutionary emergence of drug resistance? Trends Microbiol 2015; 23:126-33. [PMID: 25680587 DOI: 10.1016/j.tim.2015.01.005] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2014] [Revised: 01/12/2015] [Accepted: 01/13/2015] [Indexed: 10/24/2022]
Abstract
The emergence of drug-resistant pathogens is often considered a canonical case of evolution by natural selection. Here we argue that the strength of selection can be a poor predictor of the rate of resistance emergence. It is possible for a resistant strain to be under negative selection and still emerge in an infection or spread in a population. Measuring the right parameters is a necessary first step toward the development of evidence-based resistance-management strategies. We argue that it is the absolute fitness of the resistant strains that matters most and that a primary determinant of the absolute fitness of a resistant strain is the ecological context in which it finds itself.
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Affiliation(s)
- Troy Day
- Department of Mathematics and Statistics, Jeffery Hall, Queen's University, Kingston, ON K7L 3N6, Canada; Department of Biology, Queen's University, Kingston, ON K7L 3N6, Canada; The Fogarty International Center, National Institutes of Health, Bethesda, MD 20892, USA.
| | - Silvie Huijben
- ISGlobal, Barcelona Centre for International Health Research (CRESIB), Hospital Clínic, Universitat de Barcelona, Barcelona, Spain
| | - Andrew F Read
- The Fogarty International Center, National Institutes of Health, Bethesda, MD 20892, USA; Center for Infectious Disease Dynamics, Departments of Biology and Entomology, Pennsylvania State University, University Park, PA 16802, USA
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132
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Rodriguez de Evgrafov M, Gumpert H, Munck C, Thomsen TT, Sommer MOA. Collateral Resistance and Sensitivity Modulate Evolution of High-Level Resistance to Drug Combination Treatment in Staphylococcus aureus. Mol Biol Evol 2015; 32:1175-85. [PMID: 25618457 DOI: 10.1093/molbev/msv006] [Citation(s) in RCA: 70] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
As drug-resistant pathogens continue to emerge, combination therapy will increasingly be relied upon to treat infections and to help combat further development of multidrug resistance. At present a dichotomy exists between clinical practice, which favors therapeutically synergistic combinations, and the scientific model emerging from in vitro experimental work, which maintains that this interaction provides greater selective pressure toward resistance development than other interaction types. We sought to extend the current paradigm, based on work below or near minimum inhibitory concentration levels, to reflect drug concentrations more likely to be encountered during treatment. We performed a series of adaptive evolution experiments using Staphylococcus aureus. Interestingly, no relationship between drug interaction type and resistance evolution was found as resistance increased significantly beyond wild-type levels. All drug combinations, irrespective of interaction types, effectively limited resistance evolution compared with monotreatment. Cross-resistance and collateral sensitivity were found to be important factors in the extent of resistance evolution toward a combination. Comparative genomic analyses revealed that resistance to drug combinations was mediated largely by mutations in the same genes as single-drug-evolved lineages highlighting the importance of the component drugs in determining the rate of resistance evolution. Results of this work suggest that the mechanisms of resistance to constituent drugs should be the focus of future resistance evolution work.
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Affiliation(s)
| | - Heidi Gumpert
- Department of Systems Biology, Technical University of Denmark, Lyngby, Denmark
| | - Christian Munck
- Department of Systems Biology, Technical University of Denmark, Lyngby, Denmark
| | - Thomas T Thomsen
- Department of Systems Biology, Technical University of Denmark, Lyngby, Denmark
| | - Morten O A Sommer
- Department of Systems Biology, Technical University of Denmark, Lyngby, Denmark The Novo Nordisk Foundation Center for Biosustainability, Technical University of Denmark, Hørsholm, Denmark
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133
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Dunn AM, Hatcher MJ. Parasites and biological invasions: parallels, interactions, and control. Trends Parasitol 2015; 31:189-99. [PMID: 25613560 DOI: 10.1016/j.pt.2014.12.003] [Citation(s) in RCA: 124] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2014] [Revised: 12/05/2014] [Accepted: 12/11/2014] [Indexed: 10/24/2022]
Abstract
Species distributions are changing at an unprecedented rate owing to human activity. We examine how two key processes of redistribution - biological invasion and disease emergence - are interlinked. There are many parallels between invasion and emergence processes, and invasions can drive the spread of new diseases to wildlife. We examine the potential impacts of invasion and disease emergence, and discuss how these threats can be countered, focusing on biosecurity. In contrast with international policy on emerging diseases of humans and managed species, policy on invasive species and parasites of wildlife is fragmented, and the lack of international cooperation encourages individual parties to minimize their input into control. We call for international policy that acknowledges the strong links between emerging diseases and invasion risk.
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Affiliation(s)
- Alison M Dunn
- School of Biology, University of Leeds, Leeds LS2 9JT, UK.
| | - Melanie J Hatcher
- School of Biology, University of Leeds, Leeds LS2 9JT, UK; School of Biological Sciences, University of Bristol, Bristol BS8 1TH, UK
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134
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Abstract
Populations can evolve to adapt to external changes. The capacity to evolve and adapt makes successful treatment of infectious diseases and cancer difficult. Indeed, therapy resistance has become a key challenge for global health. Therefore, ideas of how to control evolving populations to overcome this threat are valuable. Here we use the mathematical concepts of stochastic optimal control to study what is needed to control evolving populations. Following established routes to calculate control strategies, we first study how a polymorphism can be maintained in a finite population by adaptively tuning selection. We then introduce a minimal model of drug resistance in a stochastically evolving cancer cell population and compute adaptive therapies. When decisions are in this manner based on monitoring the response of the tumor, this can outperform established therapy paradigms. For both case studies, we demonstrate the importance of high-resolution monitoring of the target population to achieve a given control objective, thus quantifying the intuition that to control, one must monitor.
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135
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Abstract
During the past century, discoveries of microorganisms as causes of infections and antibiotics as effective therapeutic agents have contributed to significant gains in public health in many parts of the world. Health agencies worldwide are galvanizing attention toward antibiotic resistance, which is a major threat to public health (Centers for Disease Control and Prevention, 2013; World Health Organization, 2014). Some life scientists believe that we are approaching the post-antibiotic age (Davies & Davies, 2010). The growing threat of antimicrobial resistance is fueled by complex factors with biological, behavioral, and societal aspects. This primer provides an overview of antibiotic resistance and its growing burden on public health, the biological and behavioral mechanisms that increase antibiotic resistance, and examples of where health communication scholars can contribute to efforts to make our current antibiotic drugs last as long as possible. In addition, we identify compelling challenges for current communication theories and practices.
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Affiliation(s)
- Rachel A Smith
- a Department of Communication Arts & Sciences , Pennsylvania State University
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136
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Baquero F, Lanza VF, Cantón R, Coque TM. Public health evolutionary biology of antimicrobial resistance: priorities for intervention. Evol Appl 2014; 8:223-39. [PMID: 25861381 PMCID: PMC4380917 DOI: 10.1111/eva.12235] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2014] [Accepted: 10/12/2014] [Indexed: 12/19/2022] Open
Abstract
The three main processes shaping the evolutionary ecology of antibiotic resistance (AbR) involve the emergence, invasion and occupation by antibiotic-resistant genes of significant environments for human health. The process of emergence in complex bacterial populations is a high-frequency, continuous swarming of ephemeral combinatory genetic and epigenetic explorations inside cells and among cells, populations and communities, expanding in different environments (migration), creating the stochastic variation required for evolutionary progress. Invasion refers to the process by which AbR significantly increases in frequency in a given (invaded) environment, led by external invaders local multiplication and spread, or by endogenous conversion. Conversion occurs because of the spread of AbR genes from an exogenous resistant clone into an established (endogenous) bacterial clone(s) colonizing the environment; and/or because of dissemination of particular resistant genetic variants that emerged within an endogenous clonal population. Occupation of a given environment by a resistant variant means a permanent establishment of this organism in this environment, even in the absence of antibiotic selection. Specific interventions on emergence influence invasion, those acting on invasion also influence occupation and interventions on occupation determine emergence. Such interventions should be simultaneously applied, as they are not simple solutions to the complex problem of AbR.
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Affiliation(s)
- Fernando Baquero
- Departamento de Microbiología, Hospital Universitario Ramón y Cajal, Instituto Ramón y Cajal de Investigación Sanitaria (IRYCIS) Madrid, Spain ; Unidad de Resistencia a Antibióticos y Virulencia Bacteriana asociada al Consejo Superior de Investigaciones Científicas (CSIC) Madrid, Spain ; CIBER Epidemiología y Salud Pública (CIBERESP) Madrid, Spain
| | - Val F Lanza
- Departamento de Microbiología, Hospital Universitario Ramón y Cajal, Instituto Ramón y Cajal de Investigación Sanitaria (IRYCIS) Madrid, Spain ; Unidad de Resistencia a Antibióticos y Virulencia Bacteriana asociada al Consejo Superior de Investigaciones Científicas (CSIC) Madrid, Spain ; CIBER Epidemiología y Salud Pública (CIBERESP) Madrid, Spain
| | - Rafael Cantón
- Departamento de Microbiología, Hospital Universitario Ramón y Cajal, Instituto Ramón y Cajal de Investigación Sanitaria (IRYCIS) Madrid, Spain ; Unidad de Resistencia a Antibióticos y Virulencia Bacteriana asociada al Consejo Superior de Investigaciones Científicas (CSIC) Madrid, Spain ; Spanish Network for the Research in Infectious Diseases (REIPI RD12/0015), Instituto de Salud Carlos III Madrid, Spain
| | - Teresa M Coque
- Departamento de Microbiología, Hospital Universitario Ramón y Cajal, Instituto Ramón y Cajal de Investigación Sanitaria (IRYCIS) Madrid, Spain ; Unidad de Resistencia a Antibióticos y Virulencia Bacteriana asociada al Consejo Superior de Investigaciones Científicas (CSIC) Madrid, Spain ; CIBER Epidemiología y Salud Pública (CIBERESP) Madrid, Spain
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137
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Hansen J, Day T. Coinfection and the evolution of drug resistance. J Evol Biol 2014; 27:2595-604. [DOI: 10.1111/jeb.12518] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2014] [Accepted: 09/02/2014] [Indexed: 11/29/2022]
Affiliation(s)
- J. Hansen
- Department of Mathematics and Statistics; Jeffery Hall; Queen's University; Kingston ON Canada
| | - T. Day
- Department of Mathematics and Statistics; Jeffery Hall; Queen's University; Kingston ON Canada
- Department of Biology; Queen's University; Kingston ON Canada
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138
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Establishment of macrocyclic lactone resistant Dirofilaria immitis isolates in experimentally infected laboratory dogs. Parasit Vectors 2014; 7:494. [PMID: 25376278 PMCID: PMC4228187 DOI: 10.1186/s13071-014-0494-6] [Citation(s) in RCA: 64] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2014] [Accepted: 10/21/2014] [Indexed: 12/15/2022] Open
Abstract
BACKGROUND Strains of Dirofilaria immitis suspected of lack of efficacy (LOE) to macrocyclic lactone (ML) preventive drugs have been increasingly reported in dogs by practicing veterinarians since 2005 in the Lower Mississippi Delta region. If proven, and not controlled in the early stages, the emergence of ML drug resistance threatens to become a widespread problem in the US that may limit the effectiveness of current preventive drug treatment methods. METHODS To validate practice reports, a statewide survey of Louisiana veterinarians was done to define the extent of the problem and identify focal 'hotspots' of reported ML LOEs using Geographic Information Systems (GIS) methods. The present study then utilized microfilariae (Mf) from two canine field cases from different state locations that fit criteria for a high index of suspicion of LOE against heartworms by ML drugs. Blood containing Mf from the canine field cases was used to infect and produce L3 in Aedes aegypti for experimental infection of two groups of dogs, each of which contained two laboratory dogs, one treated with prophylactic ivermectin (12 μg/kg) monthly for 6 months at twice the label dose (6 μg/kg), and one untreated control. RESULTS Both treated and untreated dogs from Group I and Group II developed patent D. immitis infections by 218 DPI and 189 DPI, respectively, as evidenced by a positive occult heartworm antigen test and microfilaremia by the Knott's test. Mf counts gradually increased post-patency in test and control dogs. Infective larvae raised from microfilariae from the treated Group I dog were used to successfully establish a second generation isolate, confirming heritability of resistance in the face of a monthly ivermectin challenge dose of 24 μg/kg, given monthly for 3 months. CONCLUSIONS These experimental infection studies provide in vivo evidence of the existence of ML drug resistance in dogs infected by D. immitis L3 from suspect field LOE cases in the Lower Mississippi Delta. Results encourage further work on mechanisms underlying the emergence of ML resistance in D. immitis and development of evidence-based resistance management strategies for heartworm preventives in order to extend the useful life of current drugs.
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139
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Read AF, Woods RJ. Antibiotic resistance management. EVOLUTION MEDICINE AND PUBLIC HEALTH 2014; 2014:147. [PMID: 25355275 PMCID: PMC4228198 DOI: 10.1093/emph/eou024] [Citation(s) in RCA: 110] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Affiliation(s)
- Andrew F Read
- Center for Infectious Disease Dynamics, The Pennsylvania State University, University Park, PA 16802, USA and Division of Infectious Diseases, University of Michigan, Ann Arbor, MI 48109, USA
| | - Robert J Woods
- Center for Infectious Disease Dynamics, The Pennsylvania State University, University Park, PA 16802, USA and Division of Infectious Diseases, University of Michigan, Ann Arbor, MI 48109, USA
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140
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Carroll SP, Jørgensen PS, Kinnison MT, Bergstrom CT, Denison RF, Gluckman P, Smith TB, Strauss SY, Tabashnik BE. Applying evolutionary biology to address global challenges. Science 2014; 346:1245993. [PMID: 25213376 PMCID: PMC4245030 DOI: 10.1126/science.1245993] [Citation(s) in RCA: 159] [Impact Index Per Article: 15.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Two categories of evolutionary challenges result from escalating human impacts on the planet. The first arises from cancers, pathogens, and pests that evolve too quickly and the second, from the inability of many valued species to adapt quickly enough. Applied evolutionary biology provides a suite of strategies to address these global challenges that threaten human health, food security, and biodiversity. This Review highlights both progress and gaps in genetic, developmental, and environmental manipulations across the life sciences that either target the rate and direction of evolution or reduce the mismatch between organisms and human-altered environments. Increased development and application of these underused tools will be vital in meeting current and future targets for sustainable development.
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Affiliation(s)
- Scott P Carroll
- Department of Entomology, University of California, Davis, One Shields Avenue, Davis, CA 95616, USA. Institute for Contemporary Evolution, Davis, CA 95616, USA.
| | - Peter Søgaard Jørgensen
- Center for Macroecology, Evolution and Climate, Department of Biology, University of Copenhagen, 2100 Copenhagen, Denmark. Center for Macroecology, Evolution and Climate, Natural History Museum of Denmark, University of Copenhagen, 2100 Copenhagen, Denmark.
| | - Michael T Kinnison
- School of Biology and Ecology, University of Maine, Orono, ME 04469, USA
| | - Carl T Bergstrom
- Department of Biology, University of Washington, Seattle, WA 98195, USA
| | - R Ford Denison
- Department of Ecology, Evolution, and Behavior, University of Minnesota, Minneapolis, MN 55108, USA
| | - Peter Gluckman
- Centre for Human Evolution, Adaptation and Disease, Liggins Institute, University of Auckland, Auckland, New Zealand
| | - Thomas B Smith
- Department of Ecology and Evolutionary Biology, University of California, Los Angeles, CA 90095, USA. Center for Tropical Research, Institute of the Environment and Sustainability, University of California, Los Angeles, 619 Charles E. Young Drive East, Los Angeles, 90095-1496, CA
| | - Sharon Y Strauss
- Department of Evolution and Ecology and Center for Population Biology, University of California, Davis, One Shields Avenue, CA 95616, USA
| | - Bruce E Tabashnik
- Department of Entomology, University of Arizona, Tucson, AZ 85721, USA
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141
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Alexander HK, Martin G, Martin OY, Bonhoeffer S. Evolutionary rescue: linking theory for conservation and medicine. Evol Appl 2014; 7:1161-79. [PMID: 25558278 PMCID: PMC4275089 DOI: 10.1111/eva.12221] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2014] [Accepted: 09/16/2014] [Indexed: 02/01/2023] Open
Abstract
Evolutionary responses that rescue populations from extinction when drastic environmental changes occur can be friend or foe. The field of conservation biology is concerned with the survival of species in deteriorating global habitats. In medicine, in contrast, infected patients are treated with chemotherapeutic interventions, but drug resistance can compromise eradication of pathogens. These contrasting biological systems and goals have created two quite separate research communities, despite addressing the same central question of whether populations will decline to extinction or be rescued through evolution. We argue that closer integration of the two fields, especially of theoretical understanding, would yield new insights and accelerate progress on these applied problems. Here, we overview and link mathematical modelling approaches in these fields, suggest specific areas with potential for fruitful exchange, and discuss common ideas and issues for empirical testing and prediction.
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Affiliation(s)
- Helen K Alexander
- Institute for Integrative Biology, D-USYS, ETH Zürich Zürich, Switzerland
| | - Guillaume Martin
- Institut des Sciences de l'Evolution, UMR 5554, Université Montpellier 2 - CNRS - IRD Montpellier Cedex, France
| | - Oliver Y Martin
- Institute for Integrative Biology, D-USYS, ETH Zürich Zürich, Switzerland
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142
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Torres-Barceló C, Arias-Sánchez FI, Vasse M, Ramsayer J, Kaltz O, Hochberg ME. A window of opportunity to control the bacterial pathogen Pseudomonas aeruginosa combining antibiotics and phages. PLoS One 2014; 9:e106628. [PMID: 25259735 PMCID: PMC4178015 DOI: 10.1371/journal.pone.0106628] [Citation(s) in RCA: 100] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2014] [Accepted: 07/25/2014] [Indexed: 01/09/2023] Open
Abstract
The evolution of antibiotic resistance in bacteria is a global concern and the use of bacteriophages alone or in combined therapies is attracting increasing attention as an alternative. Evolutionary theory predicts that the probability of bacterial resistance to both phages and antibiotics will be lower than to either separately, due for example to fitness costs or to trade-offs between phage resistance mechanisms and bacterial growth. In this study, we assess the population impacts of either individual or combined treatments of a bacteriophage and streptomycin on the nosocomial pathogen Pseudomonas aeruginosa. We show that combining phage and antibiotics substantially increases bacterial control compared to either separately, and that there is a specific time delay in antibiotic introduction independent of antibiotic dose, that minimizes both bacterial density and resistance to either antibiotics or phage. These results have implications for optimal combined therapeutic approaches.
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Affiliation(s)
- Clara Torres-Barceló
- Institut des Sciences de l'Evolution, CNRS-Université Montpellier 2, Montpellier, France
- * E-mail: (CTB); (MEH)
| | - Flor I. Arias-Sánchez
- Institut des Sciences de l'Evolution, CNRS-Université Montpellier 2, Montpellier, France
| | - Marie Vasse
- Institut des Sciences de l'Evolution, CNRS-Université Montpellier 2, Montpellier, France
| | - Johan Ramsayer
- Institut des Sciences de l'Evolution, CNRS-Université Montpellier 2, Montpellier, France
| | - Oliver Kaltz
- Institut des Sciences de l'Evolution, CNRS-Université Montpellier 2, Montpellier, France
| | - Michael E. Hochberg
- Institut des Sciences de l'Evolution, CNRS-Université Montpellier 2, Montpellier, France
- Santa Fe Institute, Santa Fe, New Mexico, United States of America
- Wissenshaftskolleg zu Berlin, Berlin, Germany
- * E-mail: (CTB); (MEH)
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143
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Pollitt LC, Sim D, Salathé R, Read AF. Understanding genetic variation in in vivo tolerance to artesunate: implications for treatment efficacy and resistance monitoring. Evol Appl 2014; 8:296-304. [PMID: 25861387 PMCID: PMC4380923 DOI: 10.1111/eva.12194] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2014] [Accepted: 05/20/2014] [Indexed: 01/10/2023] Open
Abstract
Artemisinin-based drugs are the front-line weapon in the treatment of human malaria cases, but there is concern that recent reports of slow clearing infections may signal developing resistance to treatment. In the absence of molecular markers for resistance, current efforts to monitor drug efficacy are based on the rate at which parasites are cleared from infections. However, some knowledge of the standing variation in parasite susceptibility is needed to identify a meaningful increase in infection half-life. Here, we show that five previously unexposed genotypes of the rodent malaria parasite Plasmodium chabaudi differ substantially in their in vivo response to treatment. Slower clearance rates were not linked to parasite virulence or growth rate, going against the suggestion that drug treatment will drive the evolution of virulence in this system. The level of variation observed here in a relatively small number of genotypes suggests existing ‘resistant’ parasites could be present in the population and therefore, increased parasite clearance rates could represent selection on pre-existing variation rather than de novo resistance events. This has implications for resistance monitoring as susceptibility may depend on evolved traits unrelated to drug exposure.
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Affiliation(s)
- Laura C Pollitt
- Center for Infectious Disease Dynamics, Department of Biology, Pennsylvania State University University Park, PA, USA ; Centre for Immunity, Infection and Evolution, University of Edinburgh Edinburgh, UK
| | - Derek Sim
- Center for Infectious Disease Dynamics, Department of Biology, Pennsylvania State University University Park, PA, USA
| | - Rahel Salathé
- Center for Infectious Disease Dynamics, Department of Biology, Pennsylvania State University University Park, PA, USA
| | - Andrew F Read
- Center for Infectious Disease Dynamics, Department of Biology, Pennsylvania State University University Park, PA, USA ; Department of Entomology, The Pennsylvania State University University Park, PA, USA ; Fogarty International Center, National Institutes of Health Bethesda, MD, USA
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144
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Xie J, Gou Y, Zhao Q, Wang K, Yang X, Yan J, Zhang W, Zhang B, Ma C, Wang R. Antimicrobial activities and membrane-active mechanism of CPF-C1 against multidrug-resistant bacteria, a novel antimicrobial peptide derived from skin secretions of the tetraploid frogXenopus clivii. J Pept Sci 2014; 20:876-84. [DOI: 10.1002/psc.2679] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2014] [Revised: 06/21/2014] [Accepted: 07/01/2014] [Indexed: 11/06/2022]
Affiliation(s)
- Junqiu Xie
- Key Laboratory of Preclinical Study for New Drugs of Gansu Province, School of Basic Medical Sciences; Lanzhou University; Lanzhou China
| | - Yuanmei Gou
- Key Laboratory of Preclinical Study for New Drugs of Gansu Province, School of Basic Medical Sciences; Lanzhou University; Lanzhou China
| | - Qian Zhao
- Key Laboratory of Preclinical Study for New Drugs of Gansu Province, School of Basic Medical Sciences; Lanzhou University; Lanzhou China
| | - Kairong Wang
- Key Laboratory of Preclinical Study for New Drugs of Gansu Province, School of Basic Medical Sciences; Lanzhou University; Lanzhou China
| | - Xiongli Yang
- Key Laboratory of Preclinical Study for New Drugs of Gansu Province, School of Basic Medical Sciences; Lanzhou University; Lanzhou China
| | - Jiexi Yan
- Key Laboratory of Preclinical Study for New Drugs of Gansu Province, School of Basic Medical Sciences; Lanzhou University; Lanzhou China
| | - Wei Zhang
- Key Laboratory of Preclinical Study for New Drugs of Gansu Province, School of Basic Medical Sciences; Lanzhou University; Lanzhou China
| | - Bangzhi Zhang
- Key Laboratory of Preclinical Study for New Drugs of Gansu Province, School of Basic Medical Sciences; Lanzhou University; Lanzhou China
| | - Chi Ma
- Key Laboratory of Preclinical Study for New Drugs of Gansu Province, School of Basic Medical Sciences; Lanzhou University; Lanzhou China
| | - Rui Wang
- Key Laboratory of Preclinical Study for New Drugs of Gansu Province, School of Basic Medical Sciences; Lanzhou University; Lanzhou China
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145
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Levin BR, Baquero F, Johnsen PJ. A model-guided analysis and perspective on the evolution and epidemiology of antibiotic resistance and its future. Curr Opin Microbiol 2014; 19:83-89. [PMID: 25016172 DOI: 10.1016/j.mib.2014.06.004] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2014] [Revised: 06/11/2014] [Accepted: 06/11/2014] [Indexed: 01/06/2023]
Abstract
A simple epidemiological model is used as a framework to explore the potential efficacy of measures to control antibiotic resistance in community-based self-limiting human infections. The analysis of the properties of this model predict that resistance can be maintained at manageable levels if: first, the rates at which specific antibiotics are used declines with the frequency of resistance to these drugs; second, resistance rarely emerges during therapy; and third, external sources rarely contribute to the entry of resistant bacteria into the community. We discuss the feasibility and limitations of these measures to control the rates of antibiotic resistance and the potential of advances in diagnostic procedures to facilitate this endeavor.
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Affiliation(s)
- Bruce R Levin
- Department of Biology Emory University, Atlanta, GA, USA.
| | - Fernando Baquero
- Ramón y Cajal Institute for Health Research (IRYCIS), Ramón y Cajal University Hospital, Madrid, Spain
| | - Pål J Johnsen
- Department of Pharmacy, UiT, The Arctic University, Tromsø, Norway
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146
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Kim Y, Escalante AA, Schneider KA. A population genetic model for the initial spread of partially resistant malaria parasites under anti-malarial combination therapy and weak intrahost competition. PLoS One 2014; 9:e101601. [PMID: 25007207 PMCID: PMC4090191 DOI: 10.1371/journal.pone.0101601] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2014] [Accepted: 06/09/2014] [Indexed: 11/18/2022] Open
Abstract
To develop public-health policies that extend the lifespan of affordable anti-malarial drugs as effective treatment options, it is necessary to understand the evolutionary processes leading to the origin and spread of mutations conferring drug resistance in malarial parasites. We built a population-genetic model for the emergence of resistance under combination drug therapy. Reproductive cycles of parasites are specified by their absolute fitness determined by clinical parameters, thus coupling the evolutionary-genetic with population-dynamic processes. Initial mutations confer only partial drug-resistance. Therefore, mutant parasites rarely survive combination therapy and within-host competition is very weak among parasites. The model focuses on the early phase of such unsuccessful recurrent mutations. This ends in the rare event of mutants enriching in an infected individual from which the successful spread of resistance over the entire population is initiated. By computer simulations, the waiting time until the establishment of resistant parasites is analysed. Resistance spreads quickly following the first appearance of a host infected predominantly by mutant parasites. This occurs either through a rare transmission of a resistant parasite to an uninfected host or through a rare failure of drugs in removing "transient" mutant alleles. The emergence of resistance is delayed with lower mutation rate, earlier treatment, higher metabolic cost of resistance, longer duration of high drug dose, and higher drug efficacy causing a stronger reduction in the sensitive and resistant parasites' fitnesses. Overall, contrary to other studies' proposition, the current model based on absolute fitness suggests that aggressive drug treatment delays the emergence of drug resistance.
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Affiliation(s)
- Yuseob Kim
- Department of Life Science and Division of EcoScience, Ewha Womans University, Seoul, South Korea
- * E-mail:
| | - Ananias A. Escalante
- School of Life Sciences and Center for Evolutionary Medicine and Informatics at the Biodesign Institute, Arizona State University, Tempe, Arizona, United States of America
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147
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Baquero F, Coque TM, Cantón R. Counteracting antibiotic resistance: breaking barriers among antibacterial strategies. Expert Opin Ther Targets 2014; 18:851-61. [DOI: 10.1517/14728222.2014.925881] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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148
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Emergence of resistance to atovaquone-proguanil in malaria parasites: insights from computational modeling and clinical case reports. Antimicrob Agents Chemother 2014; 58:4504-14. [PMID: 24867967 DOI: 10.1128/aac.02550-13] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
The usefulness of atovaquone-proguanil (AP) as an antimalarial treatment is compromised by the emergence of atovaquone resistance during therapy. However, the origin of the parasite mitochondrial DNA (mtDNA) mutation conferring atovaquone resistance remains elusive. Here, we report a patient-based stochastic model that tracks the intrahost emergence of mutations in the multicopy mtDNA during the first erythrocytic parasite cycles leading to the malaria febrile episode. The effect of mtDNA copy number, mutation rate, mutation cost, and total parasite load on the mutant parasite load per patient was evaluated. Computer simulations showed that almost any infected patient carried, after four to seven erythrocytic cycles, de novo mutant parasites at low frequency, with varied frequencies of parasites carrying varied numbers of mutant mtDNA copies. A large interpatient variability in the size of this mutant reservoir was found; this variability was due to the different parameters tested but also to the relaxed replication and partitioning of mtDNA copies during mitosis. We also report seven clinical cases in which AP-resistant infections were treated by AP. These provided evidence that parasiticidal drug concentrations against AP-resistant parasites were transiently obtained within days after treatment initiation. Altogether, these results suggest that each patient carries new mtDNA mutant parasites that emerge before treatment but are killed by high starting drug concentrations. However, because the size of this mutant reservoir is highly variable from patient to patient, we propose that some patients fail to eliminate all of the mutant parasites, repeatedly producing de novo AP treatment failures.
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149
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Exploring the collaboration between antibiotics and the immune response in the treatment of acute, self-limiting infections. Proc Natl Acad Sci U S A 2014; 111:8331-8. [PMID: 24843148 DOI: 10.1073/pnas.1400352111] [Citation(s) in RCA: 87] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
The successful treatment of bacterial infections is the product of a collaboration between antibiotics and the host's immune defenses. Nevertheless, in the design of antibiotic treatment regimens, few studies have explored the combined action of antibiotics and the immune response to clearing infections. Here, we use mathematical models to examine the collective contribution of antibiotics and the immune response to the treatment of acute, self-limiting bacterial infections. Our models incorporate the pharmacokinetics and pharmacodynamics of the antibiotics, the innate and adaptive immune responses, and the population and evolutionary dynamics of the target bacteria. We consider two extremes for the antibiotic-immune relationship: one in which the efficacy of the immune response in clearing infections is directly proportional to the density of the pathogen; the other in which its action is largely independent of this density. We explore the effect of antibiotic dose, dosing frequency, and term of treatment on the time before clearance of the infection and the likelihood of antibiotic-resistant bacteria emerging and ascending. Our results suggest that, under most conditions, high dose, full-term therapy is more effective than more moderate dosing in promoting the clearance of the infection and decreasing the likelihood of emergence of antibiotic resistance. Our results also indicate that the clinical and evolutionary benefits of increasing antibiotic dose are not indefinite. We discuss the current status of data in support of and in opposition to the predictions of this study, consider those elements that require additional testing, and suggest how they can be tested.
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150
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Peña-Miller R, Fuentes-Hernandez A, Reding C, Gudelj I, Beardmore R. Testing the optimality properties of a dual antibiotic treatment in a two-locus, two-allele model. J R Soc Interface 2014; 11:20131035. [PMID: 24812050 DOI: 10.1098/rsif.2013.1035] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
Mathematically speaking, it is self-evident that the optimal control of complex, dynamical systems with many interacting components cannot be achieved with 'non-responsive' control strategies that are constant through time. Although there are notable exceptions, this is usually how we design treatments with antimicrobial drugs when we give the same dose and the same antibiotic combination each day. Here, we use a frequency- and density-dependent pharmacogenetics mathematical model based on a standard, two-locus, two-allele representation of how bacteria resist antibiotics to probe the question of whether optimal antibiotic treatments might, in fact, be constant through time. The model describes the ecological and evolutionary dynamics of different sub-populations of the bacterium Escherichia coli that compete for a single limiting resource in a two-drug environment. We use in vitro evolutionary experiments to calibrate and test the model and show that antibiotic environments can support dynamically changing and heterogeneous population structures. We then demonstrate, theoretically and empirically, that the best treatment strategies should adapt through time and constant strategies are not optimal.
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Affiliation(s)
- Rafael Peña-Miller
- Centro de Ciencias Genómicas, Universidad Nacional Autónoma de México, , Cuernavaca, Morelos, México
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