scholarly journals Environmental changes bridge evolutionary valleys

2016 ◽  
Vol 2 (1) ◽  
pp. e1500921 ◽  
Author(s):  
Barrett Steinberg ◽  
Marc Ostermeier
Keyword(s):  
Antibiotic Resistance ◽  
Negative Selection ◽  
Environmental Changes ◽  
Fitness Landscape ◽  
Antibiotic Resistance Gene ◽  
Evolutionary Strategies ◽  
Evolutionary Mechanisms ◽  
Inaccessible Area ◽  
Evolutionary Pathways ◽  
Open Question

In the basic fitness landscape metaphor for molecular evolution, evolutionary pathways are presumed to follow uphill steps of increasing fitness. How evolution can cross fitness valleys is an open question. One possibility is that environmental changes alter the fitness landscape such that low-fitness sequences reside on a hill in alternate environments. We experimentally test this hypothesis on the antibiotic resistance gene TEM-15 β-lactamase by comparing four evolutionary strategies shaped by environmental changes. The strategy that included initial steps of selecting for low antibiotic resistance (negative selection) produced superior alleles compared with the other three strategies. We comprehensively examined possible evolutionary pathways leading to one such high-fitness allele and found that an initially deleterious mutation is key to the allele’s evolutionary history. This mutation is an initial gateway to an otherwise relatively inaccessible area of sequence space and participates in higher-order, positive epistasis with a number of neutral to slightly beneficial mutations. The ability of negative selection and environmental changes to provide access to novel fitness peaks has important implications for natural evolutionary mechanisms and applied directed evolution.

scholarly journals Within-host competition modulates pneumococcal antibiotic resistance in the pre-vaccination era

2020 ◽  
Author(s):  
José Lourenço ◽  
Yair Daon ◽  
Andrea Gori ◽  
Uri Obolski
Keyword(s):  
Antibiotic Resistance ◽  
Antibiotic Treatment ◽  
Host Population ◽  
Pneumococcal Infections ◽  
Evolutionary Mechanisms ◽  
Antibiotic Resistant ◽  
Country Level ◽  
Modelling Framework ◽  
Public Health Challenge ◽  
Open Question

AbstractBackgroundAntibiotic treatment is a key tool in the fight against pneumococcal infections. However, the ongoing emergence of antibiotic resistant strains and high frequencies of antibiotic resistance of pneumococci pose a major public health challenge. How and which ecological and evolutionary mechanisms help maintain the coexistence of strains susceptible and resistant to antibiotic treatment remains largely an open question.Methods/resultsExpanding on a Streptococcus pneumoniae modelling framework, we here explore how both between- and within-host mechanisms of transmission can sustain observed levels of pneumococcal resistance to antibiotics in the pre-vaccination era using a stochastic, individual-based model. Our framework considers that within-host competition for co-colonization between resistant and susceptible strains can arise via pre-existing immunity (immunological competition) or intrinsic fitness differences due to resistance costs (ecological competition). We find that beyond stochasticity, host-population structure or movement at the between-host level, competition at the within-host level can explain observed variation in resistance frequencies.ConclusionIn a series of simulated scenarios informed by observed pneumococcal data in the European region, we demonstrate that ecological competition for co-colonization can explain much of the variation in co-existence observed at the country level in the pre-vaccination era. This work expands our understanding of how within-host pneumococcal competition facilitates the maintenance of antibiotic resistance in the pre-vaccination era. The demonstration of the effects of such underlying, often unmeasured competition-related components of pneumococcal dynamics improves our understanding of the mechanistic drivers for the emergence and maintenance of antibiotic resistance.

scholarly journals A Universal Positive-Negative Selection System for Gene Targeting in Plants Combining an Antibiotic Resistance Gene and Its Antisense RNA

2015 ◽  
Vol 169 (1) ◽  
pp. 362-370 ◽  
Author(s):  
Ayako Nishizawa-Yokoi ◽  
Satoko Nonaka ◽  
Keishi Osakabe ◽  
Hiroaki Saika ◽  
Seiichi Toki
Keyword(s):  
Antibiotic Resistance ◽  
Resistance Gene ◽  
Gene Targeting ◽  
Antisense Rna ◽  
Negative Selection ◽  
Antibiotic Resistance Gene ◽  
Selection System

scholarly journals Pneumococcal Competition Modulates Antibiotic Resistance in the Pre-Vaccination Era: A Modelling Study

Vaccines ◽  
2021 ◽  
Vol 9 (3) ◽  
pp. 265
Author(s):  
José Lourenço ◽  
Yair Daon ◽  
Andrea Gori ◽  
Uri Obolski
Keyword(s):  
Antibiotic Resistance ◽  
Evolutionary Mechanisms ◽  
Antibiotic Resistant ◽  
High Frequencies ◽  
Modelling Framework ◽  
Public Health Challenge ◽  
Resistant Strains ◽  
Approximate Bayesian ◽  
Open Question ◽  
Resistance Data

The ongoing emergence of antibiotic resistant strains and high frequencies of antibiotic resistance of Streptococcus pneumoniae poses a major public health challenge. How and which ecological and evolutionary mechanisms maintain the coexistence of antibiotic resistant and susceptible strains remains largely an open question. We developed an individual-based, stochastic model expanding on a previous pneumococci modelling framework. We explore how between- and within-host mechanisms of competition can sustain observed levels of resistance to antibiotics in the pre-vaccination era. Our framework considers that within-host competition for co-colonization between resistant and susceptible strains can arise via pre-existing immunity (immunological competition) or intrinsic fitness differences due to resistance costs (ecological competition). We find that beyond stochasticity, population structure or movement, competition at the within-host level can explain observed resistance frequencies. We compare our simulation results to pneumococcal antibiotic resistance data in the European region using approximate Bayesian computation. Our results demonstrate that ecological competition for co-colonization can explain the variation in co-existence of resistant and susceptible pneumococci observed in the pre-vaccination era. Furthermore, we show that within-host pneumococcal competition can facilitate the maintenance of resistance in the pre-vaccination era. Accounting for these competition-related components of pneumococcal dynamics can improve our understanding of drivers for the emergence and maintenance of antibiotic resistance in pneumococci.

scholarly journals Metagenomics Analysis Reveals the Microbial Communities, Antimicrobial Resistance Gene Diversity and Potential Pathogen Transmission Risk of Two Different Landfills in China

Diversity ◽  
2021 ◽  
Vol 13 (6) ◽  
pp. 230
Author(s):  
Shan Wan ◽  
Min Xia ◽  
Jie Tao ◽  
Yanjun Pang ◽  
Fugen Yu ◽  
...  
Keyword(s):  
Antibiotic Resistance ◽  
Microbial Communities ◽  
Resistance Gene ◽  
Resistance Genes ◽  
Gene Diversity ◽  
Antibiotic Resistance Gene ◽  
Antibiotic Resistance Genes ◽  
Pathogen Transmission ◽  
Transmission Risk ◽  
Antimicrobial Resistance Gene

In this study, we used a metagenomic approach to analyze microbial communities, antibiotic resistance gene diversity, and human pathogenic bacterium composition in two typical landfills in China. Results showed that the phyla Proteobacteria, Bacteroidetes, and Actinobacteria were predominant in the two landfills, and archaea and fungi were also detected. The genera Methanoculleus, Lysobacter, and Pseudomonas were predominantly present in all samples. sul2, sul1, tetX, and adeF were the four most abundant antibiotic resistance genes. Sixty-nine bacterial pathogens were identified from the two landfills, with Klebsiella pneumoniae, Bordetella pertussis, Pseudomonas aeruginosa, and Bacillus cereus as the major pathogenic microorganisms, indicating the existence of potential environmental risk in landfills. In addition, KEGG pathway analysis indicated the presence of antibiotic resistance genes typically associated with human antibiotic resistance bacterial strains. These results provide insights into the risk of pathogens in landfills, which is important for controlling the potential secondary transmission of pathogens and reducing workers’ health risk during landfill excavation.

scholarly journals Nitric oxide (NO) elicits aminoglycoside tolerance in Escherichia coli but antibiotic resistance gene carriage and NO sensitivity have not co-evolved

2021 ◽  
Author(s):  
Cláudia A. Ribeiro ◽  
Luke A. Rahman ◽  
Louis G. Holmes ◽  
Ayrianna M. Woody ◽  
Calum M. Webster ◽  
...  
Keyword(s):  
Nitric Oxide ◽  
Antibiotic Resistance ◽  
Antibiotic Susceptibility ◽  
Bacterial Pathogens ◽  
Antibiotic Resistance Gene ◽  
Antibiotic Resistance Genes ◽  
Resistance Mechanisms ◽  
Current Work ◽  
E Coli ◽  
Respiratory Inhibitor

AbstractThe spread of multidrug-resistance in Gram-negative bacterial pathogens presents a major clinical challenge, and new approaches are required to combat these organisms. Nitric oxide (NO) is a well-known antimicrobial that is produced by the immune system in response to infection, and numerous studies have demonstrated that NO is a respiratory inhibitor with both bacteriostatic and bactericidal properties. However, given that loss of aerobic respiratory complexes is known to diminish antibiotic efficacy, it was hypothesised that the potent respiratory inhibitor NO would elicit similar effects. Indeed, the current work demonstrates that pre-exposure to NO-releasers elicits a > tenfold increase in IC50 for gentamicin against pathogenic E. coli (i.e. a huge decrease in lethality). It was therefore hypothesised that hyper-sensitivity to NO may have arisen in bacterial pathogens and that this trait could promote the acquisition of antibiotic-resistance mechanisms through enabling cells to persist in the presence of toxic levels of antibiotic. To test this hypothesis, genomics and microbiological approaches were used to screen a collection of E. coli clinical isolates for antibiotic susceptibility and NO tolerance, although the data did not support a correlation between increased carriage of antibiotic resistance genes and NO tolerance. However, the current work has important implications for how antibiotic susceptibility might be measured in future (i.e. ± NO) and underlines the evolutionary advantage for bacterial pathogens to maintain tolerance to toxic levels of NO.

Sign in / Sign up

Export Citation Format

Share Document