scholarly journals Adaptation at different points along antibiotic concentration gradients

2021 ◽  
Vol 17 (5) ◽  
Author(s):  
Mato Lagator ◽  
Hildegard Uecker ◽  
Paul Neve
Keyword(s):  
Escherichia Coli ◽  
Concentration Gradient ◽  
Management Strategies ◽  
Resistance Management ◽  
The Body ◽  
Concentration Gradients ◽  
Antibiotic Concentration ◽  
Resistance Evolution ◽  
Subsequent Selection

Antibiotic concentrations vary dramatically in the body and the environment. Hence, understanding the dynamics of resistance evolution along antibiotic concentration gradients is critical for predicting and slowing the emergence and spread of resistance. While it has been shown that increasing the concentration of an antibiotic slows resistance evolution, how adaptation to one antibiotic concentration correlates with fitness at other points along the gradient has not received much attention. Here, we selected populations of Escherichia coli at several points along a concentration gradient for three different antibiotics, asking how rapidly resistance evolved and whether populations became specialized to the antibiotic concentration they were selected on. Populations selected at higher concentrations evolved resistance more slowly but exhibited equal or higher fitness across the whole gradient. Populations selected at lower concentrations evolved resistance rapidly, but overall fitness in the presence of antibiotics was lower. However, these populations readily adapted to higher concentrations upon subsequent selection. Our results indicate that resistance management strategies must account not only for the rates of resistance evolution but also for the fitness of evolved strains.

scholarly journals Mixtures as a Fungicide Resistance Management Tactic

2014 ◽  
Vol 104 (12) ◽  
pp. 1264-1273 ◽  
Author(s):  
Frank van den Bosch ◽  
Neil Paveley ◽  
Femke van den Berg ◽  
Peter Hobbelen ◽  
Richard Oliver
Keyword(s):  
At Risk ◽  
Disease Control ◽  
Fungicide Resistance ◽  
Management Strategies ◽  
Resistance Management ◽  
Relative Effect ◽  
Resistance Evolution ◽  
Modes Of Action ◽  
Selection For ◽  
Effective Life

We have reviewed the experimental and modeling evidence on the use of mixtures of fungicides of differing modes of action as a resistance management tactic. The evidence supports the following conclusions. 1. Adding a mixing partner to a fungicide that is at-risk of resistance (without lowering the dose of the at-risk fungicide) reduces the rate of selection for fungicide resistance. This holds for the use of mixing partner fungicides that have either multi-site or single-site modes of action. The resulting predicted increase in the effective life of the at-risk fungicide can be large enough to be of practical relevance. The more effective the mixing partner (due to inherent activity and/or dose), the larger the reduction in selection and the larger the increase in effective life of the at-risk fungicide. 2. Adding a mixing partner while lowering the dose of the at-risk fungicide reduces the selection for fungicide resistance, without compromising effective disease control. The very few studies existing suggest that the reduction in selection is more sensitive to lowering the dose of the at-risk fungicide than to increasing the dose of the mixing partner. 3. Although there are very few studies, the existing evidence suggests that mixing two at-risk fungicides is also a useful resistance management tactic. The aspects that have received too little attention to draw generic conclusions about the effectiveness of fungicide mixtures as resistance management strategies are as follows: (i) the relative effect of the dose of the two mixing partners on selection for fungicide resistance, (ii) the effect of mixing on the effective life of a fungicide (the time from introduction of the fungicide mode of action to the time point where the fungicide can no longer maintain effective disease control), (iii) polygenically determined resistance, (iv) mixtures of two at-risk fungicides, (v) the emergence phase of resistance evolution and the effects of mixtures during this phase, and (vi) monocyclic diseases and nonfoliar diseases. The lack of studies on these aspects of mixture use of fungicides should be a warning against overinterpreting the findings in this review.

The effects of local selection versus dispersal on insecticide resistance patterns: longitudinal evidence from diamondback moth (Plutella xylostella (Lepidoptera: Plutellidae)) in Australia evolving resistance to pyrethroids

2008 ◽  
Vol 98 (2) ◽  
pp. 145-157 ◽  
Author(s):  
N.M. Endersby ◽  
P.M. Ridland ◽  
A.A. Hoffmann
Keyword(s):  
Gene Flow ◽  
Plutella Xylostella ◽  
Diamondback Moth ◽  
Management Strategies ◽  
Resistance Management ◽  
Synthetic Pyrethroids ◽  
Forage Crops ◽  
Microsatellite Variation ◽  
Resistance Evolution ◽  
Local Selection

AbstractWhen strong directional selection acts on a trait, the spatial distribution of phenotypes may reflect effects of selection, as well as the spread of favoured genotypes by gene flow. Here we investigate the relative impact of these factors by assessing resistance to synthetic pyrethroids in a 12-year study of diamondback moth, Plutella xylostella, from southern Australia. We estimated resistance levels in populations from brassicaceous weeds, canola, forage crops and vegetables. Differences in resistance among local populations sampled repeatedly were stable over several years. Levels were lowest in samples from weeds and highest in vegetables. Resistance in canola samples increased over time as insecticide use increased. There was no evidence that selection in one area influenced resistance in adjacent areas. Microsatellite variation from 13 populations showed a low level of genetic variation among populations, with an AMOVA indicating that population only accounted for 0.25% of the molecular variation. This compared to an estimate of 13.8% of variation accounted for by the resistance trait. Results suggest that local selection rather than gene flow of resistance alleles dictated variation in resistance across populations. Therefore, regional resistance management strategies may not limit resistance evolution.

Modeling Glyphosate Resistance Management Strategies for Palmer Amaranth (Amaranthus palmeri) in Cotton

2011 ◽  
Vol 25 (3) ◽  
pp. 335-343 ◽  
Author(s):  
Paul Neve ◽  
Jason K. Norsworthy ◽  
Kenneth L. Smith ◽  
Ian A. Zelaya
Keyword(s):  
Weed Management ◽  
Management Strategies ◽  
Resistance Management ◽  
Glyphosate Resistance ◽  
Palmer Amaranth ◽  
Case Scenario ◽  
Management Options ◽  
Worst Case ◽  
Resistance Risk ◽  
Resistance Evolution

A simulation model is used to explore management options to mitigate risks of glyphosate resistance evolution in Palmer amaranth in glyphosate-resistant cotton in the southern United States. Our first analysis compares risks of glyphosate resistance evolution for seven weed-management strategies in continuous glyphosate-resistant cotton monoculture. In the “worst-case scenario” with five applications of glyphosate each year and no other herbicides applied, evolution of glyphosate resistance was predicted in 74% of simulated populations. In other strategies, glyphosate was applied with various combinations of preplant, PRE, and POST residual herbicides. The most effective strategy included four glyphosate applications with a preplant fomesafen application, and POST tank mixtures of glyphosate plusS-metolachlor followed by glyphosate plus flumioxazin. This strategy reduced the resistance risk to 12% of populations. A second series of simulations compared strategies where glyphosate-resistant cotton was grown in one-to-one rotations with corn or cotton with other herbicide resistance traits. In general, crop rotation reduced risks of resistance by approximately 50% and delayed the evolution of resistance by 2 to 3 yr. These analyses demonstrate that risks of glyphosate resistance evolution in Palmer amaranth can be reduced by reducing glyphosate use within and among years, controlling populations with diverse herbicide modes of action, and ensuring that population size is kept low. However, no strategy completely eliminated the risk of glyphosate resistance.

scholarly journals Within-host dynamics explain patterns of antibiotic resistance in commensal bacteria

2017 ◽  
Author(s):  
Nicholas G. Davies ◽  
Stefan Flasche ◽  
Mark Jit ◽  
Katherine E. Atkins
Keyword(s):  
Antibiotic Resistance ◽  
Management Strategies ◽  
Resistance Management ◽  
Population Level ◽  
Antibiotic Consumption ◽  
Mathematical Framework ◽  
Host Immune Responses ◽  
Resistance Evolution ◽  
Resistant Strains ◽  
The Impact

The spread of antibiotic resistance, a major threat to human health, is poorly understood. Empirically, resistant strains gradually increase in prevalence as antibiotic consumption increases, but current mathematical models predict a sharp transition between full sensitivity and full resistance. In other words, we do not understand what drives persistent coexistence between resistant and sensitive strains of disease-causing bacteria in host populations. Without knowing what drives patterns of resistance, we cannot accurately predict the impact of potential strategies for managing resistance. Here, we show that within-host dynamics—bacterial growth, strain competition, and host immune responses—promote frequency-dependent selection for resistant strains, explaining patterns of resistance at the population level. By capturing these processes in a parsimonious mathematical framework, we resolve a long-standing conflict between theory and observation. Our models capture widespread coexistence for multiple bacteria-drug combinations across 30 European countries and explain associations between carriage prevalence and resistance prevalence among bacterial subtypes. A mechanistic understanding of resistance evolution is needed to accurately forecast the impact and effectiveness of resistance-management strategies.

Comparisons Between Resistance Management Strategies for Insects and Weeds

1995 ◽  
Vol 9 (4) ◽  
pp. 830-839 ◽  
Author(s):  
Fred Gould
Keyword(s):  
Population Structure ◽  
Insecticide Resistance ◽  
Herbicide Resistance ◽  
Management Strategies ◽  
Resistance Management ◽  
Basic Research ◽  
Resistance Literature ◽  
Resistance Evolution ◽  
The Commons ◽  
Structure Lead

Problems with insecticide resistance have long plagued the field of economic entomology. Genetic, biochemical, and ecological information on insects has been used to develop strategies to slow the rate of insecticide resistance evolution. Documented cases of herbicide resistance have increased dramatically over the past 10 yr. This paper compares some aspects of insect and weed biology that can be used in determining whether or not resistance management strategies developed for insects are likely to be useful in combating herbicide resistance. Differences between insects and weeds in terms of genetic architecture, mating systems, and population structure lead to differences in the expected efficacy of some resistance management strategies. Because of the localized population structure of some weeds, it may be easier to get farmers to participate in herbicide resistance management programs and avoid a “tragedy of the commons.” A review of the herbicide resistance literature reveals a number of areas of basic research on ecology and genetics of weeds that could help in designing more appropriate resistance management programs.

Highlights of Veterinary Entomology, 2019

2020 ◽  
Vol 57 (5) ◽  
pp. 1336-1341
Author(s):  
Jimmy B Pitzer
Keyword(s):  
Biological Control ◽  
Animal Health ◽  
Management Strategies ◽  
The Body ◽  
Acaricide Resistance ◽  
Nontarget Organisms ◽  
Resistance Evolution ◽  
Body Of Knowledge ◽  
Veterinary Importance ◽  
Veterinary Entomology

Abstract Research in the field of veterinary entomology is dominated by studies concerning arthropods that affect animal health. In 2019, this research primarily addressed the overwhelming industry need to manage detrimental species such as biting flies and ticks and the ongoing problems caused by insecticide/acaricide resistance evolution in these pests. Research also included evidence supporting the need for the conservation of beneficial species, such as biological control organisms. Many studies in a variety of pest systems have demonstrated the potential detrimental effects of insecticide use on nontarget organisms, and those of veterinary importance are no exception. An emphasis also was placed on research regarding alternative management strategies for veterinary pests. The presentation herein provides a descriptive summary of selected research that contributed greatly to the body of knowledge regarding arthropods of veterinary importance. This included several studies that will pave the way towards more effective veterinary pest management in an effort to improve animal health and welfare and, therefore, the sustainability of animal agriculture.

Young Male with Bilateral ICA Dissection: Beyond CADISS Trial

2021 ◽  
pp. 251660852098428
Author(s):  
Vikas Bhatia ◽  
Chirag Jain ◽  
Sucharita Ray ◽  
jay Kumar
Keyword(s):  
Management Strategies ◽  
Young Male ◽  
Acute Onset ◽  
The Body ◽  
Artery Dissection ◽  
Cervical Artery Dissection ◽  
Stroke Study ◽  
History Of

Objective: To report a case of young male with stroke and bilateral internal carotid artery (ICA) dissection. Background: Cervical Artery Dissection in Stroke Study trial has provided some insight on management of patients with ICA dissection. However, there is a need to modify the management strategies as per specific clinical scenario. Design/Methods: Case report and literature review. Results: A 45-year-old male presented with 1 month old history of acute onset numbness of right half of the body with slurring of speech. Computed tomography angiography showed complete occlusion of left cervical ICA just beyond origin with presence of fusiform dilatation and spiral flap in right extracranial cervical ICA. The patient was started on antiplatelets and taken for endovascular procedure using 2-mesh-based carotid stents. Patient was discharged after 3 days on antiplatelet therapy. At 1-year follow-up, there were no fresh symptoms. Conclusion: This case emphasizes the role of successful endovascular management of carotid dissection in a young male. These clinical situations may not be fully represented in trials, and a case-based approach is required.

scholarly journals Vesicular Formation of Trans-Ferulic Acid: an Efficient Approach to Improve the Radical Scavenging and Antimicrobial Properties

2021 ◽  
Author(s):  
Anahita Rezaeiroshan ◽  
Majid Saeedi ◽  
Katayoun Morteza-Semnani ◽  
Jafar Akbari ◽  
Akbar Hedayatizadeh-Omran ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Reactive Oxygen Species ◽  
Ferulic Acid ◽  
Reactive Oxygen Species Production ◽  
Radical Scavenging ◽  
Reactive Oxygen ◽  
Entrapment Efficiency ◽  
The Body ◽  
Oxygen Species ◽  
Species Production

Abstract Purposes Reactive oxygen species production is harmful to human’s health. The presence of antioxidants in the body may help to diminish reactive oxygen species. Trans-ferulic acid is a good antioxidant, but its low water solubility excludes its utilization. The study aims to explore whether a vesicular drug delivery could be a way to overcome the poor absorption of trans-ferulic acid hence improving its antimicrobial efficiency and antioxidant effect. Methods Niosomal vesicles containing the drug were prepared by film hydration method. The obtained vesicles were investigated in terms of morphology, size, entrapment efficiency, release behavior, cellular cytotoxicity, antioxidant, cellular protection study, and antimicrobial evaluations. Results The optimized niosomal formulation had a particle size of 158.7 nm and entrapment efficiency of 21.64%. The results showed that the optimized formulation containing 25 μM of trans-ferulic acid could enhance the viability of human foreskin fibroblast HFF cell line against reactive oxygen species production. The minimum effective dose of the plain drug and the niosomal formulation against Staphylococcus aurous (ATCC 29213) was 750 µg/mL and 375 µg/mL, respectively, and for Escherichia coli (ATCC 25922), it was 750 µg/mL and 187/5 µg/mL, respectively. The formulation could also improve the minimum bactericidal concentration of the drug in Staphylococcus aurous, Escherichia coli, and Acinobacter baumannii (ATCC 19606). Conclusion These results revealed an improvement in both antibacterial and antioxidant effects of the drug in the niosomal formulation.

scholarly journals Foreshore Sand as a Source of Escherichia coli in Nearshore Water of a Lake Michigan Beach

2003 ◽  
Vol 69 (9) ◽  
pp. 5555-5562 ◽  
Author(s):  
Richard L. Whitman ◽  
Meredith B. Nevers
Keyword(s):  
Escherichia Coli ◽  
Lake Water ◽  
Lake Michigan ◽  
Beach Sand ◽  
Intensive Study ◽  
Concentration Gradients ◽  
Lake Water Quality ◽  
E Coli ◽  
Demographic Patterns ◽  
Hydrometeorological Conditions

ABSTRACT Swimming advisories due to excessive Escherichia coli concentrations are common at 63rd Street Beach, Chicago, Ill. An intensive study was undertaken to characterize the source and fate of E. coli in beach water and sand at the beach. From April through September 2000, water and sand samples were collected daily or twice daily at two depths on three consecutive days per week (water samples, n = 1,747; sand samples, n = 858); hydrometeorological conditions and bird and bather distributions were also recorded. E. coli concentrations in sand and water were significantly correlated, with the highest concentration being found in foreshore sand, followed by those in submerged sediment and water of increasing depth. Gull contributions to E. coli densities in sand and water were most apparent on the day following gull activity in a given area. E. coli recolonized newly placed foreshore sand within 2 weeks. Analysis of variance, correlation, cluster analyses, concentration gradients, temporal-spatial distribution, demographic patterns, and DNA fingerprinting suggest that E. coli may be able to sustain population density in temperate beach sand during summer months without external inputs. This research presents evidence that foreshore beach sand (i) plays a major role in bacterial lake water quality, (ii) is an important non-point source of E. coli to lake water rather than a net sink, (iii) may be environmentally, and perhaps hygienically, problematic, and (iv) is possibly capable of supporting an autochthonous, high density of indicator bacteria for sustained periods, independent of lake, human, or animal input.

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