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Nitrofurantoin resistance mechanism and fitness cost in Escherichia coli

TLDR
Nitrofurantoin resistance confers a reduction in fitness in E. coli in the absence of antibiotic, and even resistant mutants are probably unable to become enriched and establish an infection in the presence of therapeutic levels of nitrofurantin.
Abstract
OBJECTIVES The biological fitness cost of antibiotic resistance is a key parameter in determining the rate of appearance and spread of antibiotic-resistant bacteria. We identified mutations conferring nitrofurantoin resistance and examined their effect on the fitness of clinical Escherichia coli isolates. METHODS By plating bacterial cells on agar plates containing nitrofurantoin, spontaneous nitrofurantoin-resistant E. coli mutants were isolated. The fitness of susceptible and resistant strains was measured as growth rate in the presence and absence of nitrofurantoin in rich culture medium. Time-kill kinetics of the resistant mutants was compared with the susceptible strains. Resistance mutations were identified by DNA sequencing. RESULTS Spontaneous resistant mutants of initially susceptible clinical E. coli appeared with a rate of 10(-7)/cell/generation, and these mutants showed a reduction in the growth rate compared with the susceptible parent strain. Similarly, comparison of a set of susceptible and resistant clinical isolates of E. coli showed that the average growth rate of the resistant mutants was approximately 6% lower than the susceptible strains. Furthermore, the bacterial growth rate in the presence of nitrofurantoin at therapeutic levels was greatly reduced even for nitrofurantoin-resistant mutants. The resistance-conferring mutations were identified in the nsfA and nfsB genes that encode oxygen-insensitive nitroreductases. CONCLUSIONS Nitrofurantoin resistance confers a reduction in fitness in E. coli in the absence of antibiotic. In the presence of therapeutic levels of nitrofurantoin, even resistant mutants are so disturbed in growth that they are probably unable to become enriched and establish an infection.

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A Deep Learning Approach to Antibiotic Discovery

TL;DR: A deep neural network capable of predicting molecules with antibacterial activity is trained and a molecule from the Drug Repurposing Hub-halicin- is discovered that is structurally divergent from conventional antibiotics and displays bactericidal activity against a wide phylogenetic spectrum of pathogens.
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The genetic basis of the fitness costs of antimicrobial resistance : : a meta-analysis approach

TL;DR: The study shows that the cost of antimicrobial resistance can be partially explained by its genetic basis, and highlights both the danger associated with plasmidborne resistance and the need to understand why resistance plasmids carry a relatively low cost.
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A new strategy to fight antimicrobial resistance: the revival of old antibiotics.

TL;DR: The successful treatment of MDR bacterial infections with the use of old antibiotics is reviewed and this could represent a useful public health orientation knowing that several of these cheapest “forgotten” antibiotics are not available in many countries.
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Prediction of antibiotic resistance: time for a new preclinical paradigm?

TL;DR: It is argued that the traditional procedures that are used for the prediction of antibiotic resistance today could be markedly improved by including a broader analysis of bacterial fitness, infection dynamics, horizontal gene transfer and other factors, which will lead to more informed preclinical decisions for continuing or discontinuing the development of drug candidates.
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Evolutionary consequences of drug resistance: shared principles across diverse targets and organisms

TL;DR: Commonalities and differences related to resistance development that could guide strategies to improve therapeutic effectiveness and the development of a new generation of drugs are described.
References
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Journal ArticleDOI

The distribution of the numbers of mutants in bacterial populations.

TL;DR: Statistical calculations are made of the distribution numbers of mutants in a culture of bacteria in which the number of mutants increases on account of new mutations and of division of old mutants, which enable the mutation rate to be inferred from experiments with parallel cultures.
Journal ArticleDOI

The biological cost of antibiotic resistance

TL;DR: The data available from recent laboratory studies suggest that most, but not all, resistance-determining mutations and accessory elements engender some fitness cost, but those costs are likely to be ameliorated by subsequent evolution.
Journal ArticleDOI

The biological cost of mutational antibiotic resistance: any practical conclusions?

TL;DR: This work suggests that resistance might be reversible, provided antibiotic use is reduced and several processes act to stabilize resistance, including compensatory evolution where the fitness cost is ameliorated by additional mutation without loss of resistance.
Journal ArticleDOI

Oxygen-sensitive and -insensitive nitroreduction by Escherichia coli and rat hepatic microsomes.

TL;DR: Rat hepatic microsomes appear to metabolize nitrofurazone in a manner similar to the oxygen-sensitive E. coli reductase, suggesting that the nitro furazone anion radical is an obligate intermediate in the reduction and that the radical decays by a nonenzymatic second order process.
Journal ArticleDOI

Biological costs and mechanisms of fosfomycin resistance in Escherichia coli.

TL;DR: According to the mathematical model, the reduced growth rate of the resistant strains will prevent them from establishing in the bladder, which could explain why fosfomycin resistance remains rare in clinical isolates.
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