scholarly journals Adapt or Perish: Evolutionary Rescue in a Gradually Deteriorating Environment

Genetics ◽  
2020 ◽  
Vol 216 (2) ◽  
pp. 573-583
Author(s):  
Loïc Marrec ◽  
Anne-Florence Bitbol
Keyword(s):  
Antimicrobial Resistance ◽  
Carrying Capacity ◽  
Microbial Population ◽  
Stochastic Simulations ◽  
Extinction Time ◽  
Resistance Evolution ◽  
Mutation Probability ◽  
Evolutionary Rescue ◽  
Population Sizes ◽  
Environment Degradation

We investigate the evolutionary rescue of a microbial population in a gradually deteriorating environment, through a combination of analytical calculations and stochastic simulations. We consider a population destined for extinction in the absence of mutants, which can survive only if mutants sufficiently adapted to the new environment arise and fix. We show that mutants that appear later during the environment deterioration have a higher probability to fix. The rescue probability of the population increases with a sigmoidal shape when the product of the carrying capacity and of the mutation probability increases. Furthermore, we find that rescue becomes more likely for smaller population sizes and/or mutation probabilities if the environment degradation is slower, which illustrates the key impact of the rapidity of environment degradation on the fate of a population. We also show that our main conclusions are robust across various types of adaptive mutants, including specialist and generalist ones, as well as mutants modeling antimicrobial resistance evolution. We further express the average time of appearance of the mutants that do rescue the population and the average extinction time of those that do not. Our methods can be applied to other situations with continuously variable fitnesses and population sizes, and our analytical predictions are valid in the weak-to-moderate mutation regime.

scholarly journals Adapt or perish: Evolutionary rescue in a gradually deteriorating environment

2020 ◽  
Author(s):  
Loïc Marrec ◽  
Anne-Florence Bitbol
Keyword(s):  
Antimicrobial Resistance ◽  
Carrying Capacity ◽  
Microbial Population ◽  
Stochastic Simulations ◽  
Extinction Time ◽  
Resistance Evolution ◽  
Mutation Probability ◽  
Evolutionary Rescue ◽  
Population Sizes ◽  
Environment Degradation

AbstractWe investigate the evolutionary rescue of a microbial population in a gradually deteriorating environment, through a combination of analytical calculations and stochastic simulations. We consider a population destined for extinction in the absence of mutants, which can only survive if mutants sufficiently adapted to the new environment arise and fix. We show that mutants that appear later during the environment deterioration have a higher probability to fix. The rescue probability of the population increases with a sigmoidal shape when the product of the carrying capacity and of the mutation probability increases. Furthermore, we find that rescue becomes more likely for smaller population sizes and/or mutation probabilities if the environment degradation is slower, which illustrates the key impact of the rapidity of environment degradation on the fate of a population. We also show that our main conclusions are robust across various types of adaptive mutants, including specialist and generalist ones, as well as mutants modeling antimicrobial resistance evolution. We further express the average time of appearance of the mutants that do rescue the population and the average extinction time of those that do not. Our methods can be applied to other situations with continuously variable fitnesses and population sizes, and our analytical predictions are valid in the weak-to-moderate mutation regime.

scholarly journals Resist or perish: fate of a microbial population subjected to a periodic presence of antimicrobial

2019 ◽  
Author(s):  
Loïc Marrec ◽  
Anne-Florence Bitbol
Keyword(s):  
Antimicrobial Resistance ◽  
Stochastic Model ◽  
Death Rate ◽  
Microbial Population ◽  
Threshold Value ◽  
Microbial Populations ◽  
Population Composition ◽  
Resistance Evolution ◽  
Rare Mutations ◽  
The Impact

AbstractThe evolution of antimicrobial resistance can be strongly affected by variations of antimicrobial concentration. Here, we study the impact of periodic alternations of absence and presence of antimicrobial on resistance evolution in a microbial population, using a stochastic model that includes variations of both population composition and size, and fully incorporates stochastic population extinctions. We show that fast alternations of presence and absence of antimicrobial are inefficient to eradicate the microbial population and strongly favor the establishment of resistance, unless the antimicrobial increases enough the death rate. We further demonstrate that if the period of alternations is longer than a threshold value, the microbial population goes extinct upon the first addition of antimicrobial, if it is not rescued by resistance. We express the probability that the population is eradicated upon the first addition of antimicrobial, assuming rare mutations. Rescue by resistance can happen either if resistant mutants preexist, or if they appear after antimicrobial is added to the environment. Importantly, the latter case is fully prevented by perfect biostatic antimicrobials that completely stop division of sensitive microorganisms. By contrast, we show that the parameter regime where treatment is efficient is larger for biocidal drugs than for biostatic drugs. This sheds light on the respective merits of different antimicrobial modes of action.Author summaryAntimicrobials select for resistance, which threatens to make antimicrobials useless. Understanding the evolution of antimicrobial resistance is therefore of crucial importance. Under what circumstances are microbial populations eradicated by antimicrobials? Conversely, when are they rescued by resistance? We address these questions employing a stochastic model that incorporates variations of both population composition and size. We consider periodic alternations of absence and presence of antimicrobial, which may model a treatment. We find a threshold period above which the first phase with antimicrobial fully determines the fate of the population. Faster alternations strongly select for resistance, and are inefficient to eradicate the microbial population, unless the death rate induced by the treatment is large enough. For longer alternation periods, we calculate the probability that the microbial population gets eradicated. We further demonstrate the different merits of biostatic antimicrobials, which prevent sensitive microbes from dividing, and of biocidal ones, which kill sensitive microbes.

scholarly journals Quantifying the impact of a periodic presence of antimicrobial on resistance evolution in a homogeneous microbial population of fixed size

2018 ◽  
Author(s):  
Loïc Marrec ◽  
Anne-Florence Bitbol
Keyword(s):  
Antimicrobial Resistance ◽  
Microbial Population ◽  
Fitness Landscape ◽  
Resistant Bacteria ◽  
Fixed Size ◽  
Variable Environment ◽  
Resistance Evolution ◽  
Evolution Of Resistance ◽  
The Impact ◽  
Analytical Approaches

AbstractThe evolution of antimicrobial resistance often occurs in a variable environment, as antimicrobial is given periodically to a patient or added and removed from a medium. This environmental variability has a huge impact on the microorganisms’ fitness landscape, and thus on the evolution of resistance. Indeed, mutations conferring resistance often carry a fitness cost in the absence of antimicrobial, which may be compensated by subsequent mutations. As antimicrobial is added or removed, the relevant fitness landscape thus switches from a fitness valley to an ascending landscape or vice-versa.Here, we investigate the effect of these time-varying patterns of selection within a stochastic model. We focus on a homogeneous microbial population of fixed size subjected to a periodic alternation of phases of absence and presence of an antimicrobial that stops growth. Combining analytical approaches and stochastic simulations, we quantify how the time necessary for fit resistant bacteria to take over the microbial population depends on the period of the alternations. We demonstrate that fast alternations strongly accelerate the evolution of resistance, and that a plateau is reached once the period gets sufficiently small. Besides, the acceleration of resistance evolution is stronger for larger populations. For asymmetric alternations, featuring a different duration of the phases with and without antimicrobial, we shed light on the existence of a broad minimum of the time taken by the population to fully evolve resistance. At this minimum, if the alternations are sufficiently fast, the very first resistant mutant that appears ultimately leads to full resistance evolution within the population. This dramatic acceleration of the evolution of antimicrobial resistance likely occurs in realistic situations, and can have an important impact both in clinical and experimental situations.

scholarly journals Asymmetric competition impacts evolutionary rescue in a changing environment

2017 ◽  
Vol 284 (1857) ◽  
pp. 20170374 ◽  
Author(s):  
Courtney L. Van Den Elzen ◽  
Elizabeth J. Kleynhans ◽  
Sarah P. Otto
Keyword(s):  
Resource Availability ◽  
Competitive Exclusion ◽  
Asymmetric Competition ◽  
Distributed Resources ◽  
Changing Environment ◽  
Competitive Release ◽  
Evolutionary Response ◽  
Evolutionary Rescue ◽  
Population Sizes ◽  
Species Declines

Interspecific competition can strongly influence the evolutionary response of a species to a changing environment, impacting the chance that the species survives or goes extinct. Previous work has shown that when two species compete for a temporally shifting resource distribution, the species lagging behind the resource peak is the first to go extinct due to competitive exclusion. However, this work assumed symmetrically distributed resources and competition. Asymmetries can generate differences between species in population sizes, genetic variation and trait means. We show that asymmetric resource availability or competition can facilitate coexistence and even occasionally cause the leading species to go extinct first. Surprisingly, we also find cases where traits evolve in the opposite direction to the changing environment because of a ‘vacuum of competitive release’ created when the lagging species declines in number. Thus, the species exhibiting the slowest rate of trait evolution is not always the most likely to go extinct in a changing environment. Our results demonstrate that the extent to which species appear to be tracking environmental change and the extent to which they are preadapted to that change may not necessarily determine which species will be the winners and which will be the losers in a rapidly changing world.

scholarly journals Trends of antimicrobial resistance in Escherichia coli isolates from urine cultures of women in Jordan: A 10-year retrospective study

10.3823/849 ◽  
2020 ◽  
Vol 10 (3) ◽  
Author(s):  
Mustafa Abdulkarim Alrabayah ◽  
Nisreen Abdel-kareem Nadi ◽  
Aiman Mohammad Suleiman ◽  
Ala' Mohammad Abbad ◽  
Hadil Simon Ghanem ◽  
...  
Keyword(s):  
Antimicrobial Resistance ◽  
Medical Condition ◽  
Treatment Strategies ◽  
Causative Organism ◽  
P Value ◽  
Treatment Protocols ◽  
Efficient Treatment ◽  
Resistance Evolution ◽  
The Past ◽  
Common Medical Condition

Background: Urinary tract infection (UTI) is a common medical condition among women. E.coli is the most common causative organism. Appropriate understanding of the development of antimicrobial resistance over the past helps to establish efficient treatment strategies in the future. The study aims to discover antimicrobial resistance trends exhibited by E.coli strains isolated from women urine cultures over the past 10 years. Methods: A total of 1874 affected urine samples over the years 2009 to 2018 were collectively reviewed and classified according to the response they showed to 24 different antimicrobial disks in the laboratory. Relations between time and resistance evolutionary profiles were calculated. Results: Gentamicin (p value =0.039), Augmentin (p value =0.017), Cefoxitin (p value =0.001), Cefixime (p value =0.026) fulfilled satisfactory figures in terms of average resistance, regression of resistance, speed of resistance evolution, steadiness of performance, side effects, spectrum range and cost with high significance. Conclusion: Drugs that showed satisfactory figures are recommended for future treatment protocols in Jordan.  

scholarly journals Harvest and Conservation of Sooty Shearwaters (Puffinus Griseus) in the Marlborough Sounds, New Zealand

2021 ◽  
Author(s):  
◽  
Amelia Frances Geary
Keyword(s):  
Carrying Capacity ◽  
Environmental Variability ◽  
Island Population ◽  
Population Modelling ◽  
Demographic Stochasticity ◽  
Extrinsic Factors ◽  
Ongoing Research ◽  
Island Populations ◽  
Population Sizes ◽  
Traditional Societies

<p>Customary harvest of wildlife can be an important mechanism through which indigenous people maintain a connection with their environment. Observations built up during harvesting events are also a useful way of monitoring change over time. However, not all traditional societies have lived harmoniously with their environment. Wildlife populations can become depleted quickly if not managed sustainably. Using traditional knowledge interviews, empirical data from two island populations and population modelling, I examined the viability of two island sooty shearwater populations in the Marlborough Sounds and their resilience to resumed, low-level harvest. The biology of the sooty shearwater populations was found to closely resemble that of populations found at higher latitudes. Historic harvest by Marlborough Maori probably had an important influence on the size of present day Marlborough populations. Viability models demonstrated that these populations were experiencing very low or negative intrinsic rates of increase. Population sizes have likely been affected by previous harvest and are not at carrying capacity. The populations are therefore vulnerable to demographic stochasticity, environmental variability and extrinsic factors such as fisheries bycatch. The low and negative growth rates for populations at small sizes not at carrying capacity are of concern where harvesting is proposed. This study provides a basis for ongoing research into the population trajectories of each island population. Harvesting is possible in one population provided an appropriate monitoring regime is established prior to harvest being undertaken, to ensure the long-term viability of Marlborough Sounds' sooty shearwater populations.</p>

Characteristics and Evolution of Microbial Drug Resistance in Burnt Patients

2020 ◽  
Author(s):  
Zhifeng Huang ◽  
Yu Gan ◽  
Kun Yang ◽  
Liangdi Gao ◽  
Bing Xiong ◽  
...  
Keyword(s):  
Antibiotic Resistance ◽  
Antimicrobial Resistance ◽  
Temporal Trends ◽  
Public Health Issue ◽  
Burn Treatment ◽  
Burn Wounds ◽  
Microbial Drug Resistance ◽  
Resistance Evolution ◽  
Significant Difference ◽  
Resistance Patterns

Abstract Wound infection is a serious complication in burnt injury, which is a common form of trauma and an important public health issue. We investigated samples from burn and non-burn wounds for microbial characteristics and temporal trends of antibiotic resistance. Wound samples were collected from 369 burnt patients and 927 non-burnt individuals admitted from 2007 to 2017. Higher frequency of A. baumannii, K. pneumonia and P. aeruginosa were observed in samples from burnt individuals when compared to those from non-burnt patients. The prevalence of different groups of bacteria varied when the samples were stratified according to age and sex. The antimicrobial resistance profiles showed significant difference between burnt and non-burnt patients. The different temporal trends of antimicrobial resistance rates were also found, which may be critical for proper selection of antibiotics in burn treatment. The present study suggested that frequent pathogens and antibacterial resistance evolution could differ between burn wounds and other wounds. Therefore, periodic surveillance of antibiotic resistance patterns in burn unit might help physicians properly select of antibiotics for treatment.

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