Your browser doesn't support javascript.
loading
Show: 20 | 50 | 100
Results 1 - 9 de 9
Filter
Add more filters










Database
Language
Publication year range
1.
bioRxiv ; 2024 Mar 01.
Article in English | MEDLINE | ID: mdl-38903098

ABSTRACT

Plasmids are extrachromosomal genetic elements commonly found in bacteria. Plasmids are known to fuel bacterial evolution through horizontal gene transfer (HGT), but recent analyses indicate that they can also promote intragenomic adaptations. However, the role of plasmids as catalysts of bacterial evolution beyond HGT remains poorly explored. In this study, we investigate the impact of a widespread conjugative plasmid, pOXA-48, on the evolution of various multidrug-resistant clinical enterobacteria. Combining experimental and within-patient evolution analyses, we unveil that plasmid pOXA-48 promotes bacterial evolution through the transposition of plasmid-encoded insertion sequence 1 (IS1) elements. Specifically, IS1-mediated gene inactivations expedite the adaptation rate of clinical strains in vitro and foster within-patient adaptation in the gut microbiota. We decipher the mechanism underlying the plasmid-mediated surge in IS1 transposition, revealing a negative feedback loop regulated by the genomic copy number of IS1. Given the overrepresentation of IS elements in bacterial plasmids, our findings propose that plasmid-mediated IS transposition represents a crucial mechanism for swift bacterial adaptation.

2.
Nat Ecol Evol ; 6(12): 1980-1991, 2022 12.
Article in English | MEDLINE | ID: mdl-36303001

ABSTRACT

Antimicrobial resistance (AMR) in bacteria is a major threat to public health; one of the key elements in the spread and evolution of AMR in clinical pathogens is the transfer of conjugative plasmids. The drivers of AMR evolution have been studied extensively in vitro but the evolution of plasmid-mediated AMR in vivo remains poorly explored. Here, we tracked the evolution of the clinically relevant plasmid pOXA-48, which confers resistance to the last-resort antibiotics carbapenems, in a large collection of enterobacterial clones isolated from the gut of hospitalized patients. Combining genomic and experimental approaches, we first characterized plasmid diversity and the genotypic and phenotypic effects of multiple plasmid mutations on a common genetic background. Second, using cutting-edge genomic editing in wild-type multidrug-resistant enterobacteria, we dissected three cases of within-patient plasmid-mediated AMR evolution. Our results revealed compensatory evolution of plasmid-associated fitness cost and the evolution of enhanced plasmid-mediated AMR in bacteria evolving in the gut of hospitalized patients. Crucially, we observed that the evolution of pOXA-48-mediated AMR in vivo involves a pivotal trade-off between resistance levels and bacterial fitness. This study highlights the need to develop new evolution-informed approaches to tackle plasmid-mediated AMR dissemination.


Subject(s)
Anti-Bacterial Agents , Drug Resistance, Bacterial , Humans , Anti-Bacterial Agents/pharmacology , Drug Resistance, Bacterial/genetics , Plasmids/genetics , Carbapenems/pharmacology , Bacteria/genetics
3.
J Antimicrob Chemother ; 74(8): 2188-2196, 2019 08 01.
Article in English | MEDLINE | ID: mdl-31102529

ABSTRACT

BACKGROUND: Fluoroquinolones such as ciprofloxacin induce the mutagenic SOS response and increase the levels of intracellular reactive oxygen species (ROS). Both the SOS response and ROS increase bacterial mutagenesis, fuelling the emergence of resistant mutants during antibiotic treatment. Recently, there has been growing interest in developing new drugs able to diminish the mutagenic effect of antibiotics by modulating ROS production and the SOS response. OBJECTIVES: To test whether physiological concentrations of N-acetylcysteine, a clinically safe antioxidant drug currently used in human therapy, is able to reduce ROS production, SOS induction and mutagenesis in ciprofloxacin-treated bacteria without affecting antibiotic activity. METHODS: The Escherichia coli strain IBDS1 and its isogenic mutant deprived of SOS mutagenesis (TLS-) were treated with different concentrations of ciprofloxacin, N-acetylcysteine or both drugs in combination. Relevant parameters such as MICs, growth rates, ROS production, SOS induction, filamentation and antibiotic-induced mutation rates were evaluated. RESULTS: Treatment with N-acetylcysteine reduced intracellular ROS levels (by ∼40%), as well as SOS induction (by up to 75%) and bacterial filamentation caused by subinhibitory concentrations of ciprofloxacin, without affecting ciprofloxacin antibacterial activity. Remarkably, N-acetylcysteine completely abolished SOS-mediated mutagenesis. CONCLUSIONS: Collectively, our data strongly support the notion that ROS are a key factor in antibiotic-induced SOS mutagenesis and open the possibility of using N-acetylcysteine in combination with antibiotic therapy to hinder the development of antibiotic resistance.


Subject(s)
Acetylcysteine/pharmacology , Anti-Bacterial Agents/pharmacology , Escherichia coli/drug effects , Fluoroquinolones/pharmacology , Mutagenesis/drug effects , SOS Response, Genetics/drug effects , Ciprofloxacin/pharmacology , Drug Resistance, Bacterial/genetics , Escherichia coli/physiology , Escherichia coli Proteins/genetics , Microbial Sensitivity Tests , Mutation Rate , Reactive Oxygen Species/analysis
4.
J Antimicrob Chemother ; 73(11): 2960-2968, 2018 11 01.
Article in English | MEDLINE | ID: mdl-30124902

ABSTRACT

Background: Acinetobacter baumannii is intrinsically resistant to fosfomycin; however, the mechanisms underlying this resistance are poorly understood. Objectives: To identify and characterize genes that contribute to intrinsic fosfomycin resistance in A. baumannii. Methods: More than 9000 individual transposon mutants of the A. baumannii ATCC 17978 strain (fosfomycin MIC ≥1024 mg/L) were screened to identify mutations conferring increased susceptibility to fosfomycin. In-frame deletion mutants were constructed for the identified genes and their susceptibility to fosfomycin was characterized by MIC determination and growth in the presence of fosfomycin. The effects of these mutations on membrane permeability and peptidoglycan integrity were characterized. Susceptibilities to 21 antibiotics were determined for the mutant strains. Results: Screening of the transposon library identified mutants in the ampD and anmK genes, both encoding enzymes of the peptidoglycan recycling pathway, that demonstrated increased susceptibility to fosfomycin. MIC values for in-frame deletion mutants were ≥42-fold (ampD) and ≥8-fold (anmK) lower than those for the parental strain, and growth of the mutant strains in the presence of 32 mg/L fosfomycin was significantly reduced. Neither mutation resulted in increased cell permeability; however, the ampD mutant demonstrated decreased peptidoglycan integrity. Susceptibility to 21 antibiotics was minimally affected by mutations in ampD and anmK. Conclusions: This study demonstrates that AmpD and AnmK of the peptidoglycan recycling pathway contribute to intrinsic fosfomycin resistance in A. baumannii, indicating that inhibitors of these enzymes could be used in combination with fosfomycin as a novel treatment approach for MDR A. baumannii.


Subject(s)
Acinetobacter baumannii/drug effects , Acinetobacter baumannii/metabolism , Anti-Bacterial Agents/pharmacology , Drug Resistance, Bacterial , Fosfomycin/pharmacology , Peptidoglycan/metabolism , Acinetobacter baumannii/genetics , Bacterial Proteins/genetics , Cell Wall/drug effects , DNA Transposable Elements , Microbial Sensitivity Tests , Mutation , N-Acetylmuramoyl-L-alanine Amidase/genetics , Peptidoglycan/genetics
5.
Antimicrob Agents Chemother ; 60(7): 4252-8, 2016 07.
Article in English | MEDLINE | ID: mdl-27139482

ABSTRACT

Escherichia coli isolates carrying chromosomally encoded low-level-quinolone-resistant (LLQR) determinants are frequently found in urinary tract infections (UTIs). LLQR mutations are considered the first step in the evolutionary pathway producing high-level fluoroquinolone resistance. Therefore, their evolution and dissemination might influence the outcome of fluoroquinolone treatments of UTI. Previous studies support the notion that low urine pH decreases susceptibility to ciprofloxacin (CIP) in E. coli However, the effect of the urinary tract physiological parameters on the activity of ciprofloxacin against LLQR E. coli strains has received little attention. We have studied the activity of ciprofloxacin under physiological urinary tract conditions against a set of well-characterized isogenic E. coli derivatives carrying the most prevalent chromosomal mutations (ΔmarR, gyrA-S83L, gyrA-D87N, and parC-S80R and some combinations). The results presented here demonstrate that all the LLQR strains studied became resistant to ciprofloxacin (according to CLSI guidelines) under physiological conditions whereas the control strain lacking LLQR mutations did not. Moreover, the survival of some LLQR E. coli variants increased up to 100-fold after challenge with a high concentration of ciprofloxacin under UTI conditions compared to the results seen with Mueller-Hinton broth. These selective conditions could explain the high prevalence of LLQR mutations in E. coli Furthermore, our data strongly suggest that recommended methods for MIC determination produce poor estimations of CIP activity against LLQR E. coli in UTIs.


Subject(s)
Anti-Bacterial Agents/therapeutic use , Ciprofloxacin/therapeutic use , Quinolones/therapeutic use , Urinary Tract Infections/drug therapy , Urinary Tract Infections/urine , Drug Resistance, Bacterial/genetics , Escherichia coli/drug effects , Escherichia coli/pathogenicity , Escherichia coli Infections/drug therapy , Escherichia coli Infections/microbiology , Escherichia coli Infections/urine , Fluoroquinolones/therapeutic use , Genotype , Healthy Volunteers , Humans , Hydrogen-Ion Concentration , Microbial Sensitivity Tests , Mutation/genetics , Prospective Studies , Urinary Tract Infections/microbiology
6.
Antimicrob Agents Chemother ; 59(6): 3246-51, 2015.
Article in English | MEDLINE | ID: mdl-25801561

ABSTRACT

The modulating effect of N-acetylcysteine (NAC) on the activity of different antibiotics has been studied in Pseudomonas aeruginosa. Our results demonstrate that, in contrast to previous reports, only the activity of imipenem is clearly affected by NAC. MIC and checkerboard determinations indicate that the NAC-based modulation of imipenem activity is dependent mainly on OprD. SDS-PAGE of outer membrane proteins (OMPs) after NAC treatments demonstrates that NAC does not modify the expression of OprD, suggesting that NAC competitively inhibits the uptake of imipenem through OprD. Similar effects on imipenem activity were obtained with P. aeruginosa clinical isolates. Our results indicate that imipenem-susceptible P. aeruginosa strains become resistant upon simultaneous treatment with NAC and imipenem. Moreover, the generality of the observed effects of NAC on antibiotic activity was assessed with two additional bacterial species, Escherichia coli and Acinetobacter baumannii. Caution should be taken during treatments, as the activity of imipenem may be modified by physiologically attainable concentrations of NAC, particularly during intravenous and nebulized regimes.


Subject(s)
Acetylcysteine/pharmacology , Anti-Bacterial Agents/pharmacology , Imipenem/pharmacology , Porins/metabolism , Pseudomonas aeruginosa/drug effects , Pseudomonas aeruginosa/metabolism , Acinetobacter baumannii/drug effects , Escherichia coli/drug effects , Gene Expression Regulation, Bacterial/drug effects , Microbial Sensitivity Tests
7.
Mol Biol Evol ; 32(7): 1708-16, 2015 Jul.
Article in English | MEDLINE | ID: mdl-25804522

ABSTRACT

Homologous recombination promotes genetic diversity by facilitating the integration of foreign DNA and intrachromosomal gene shuffling. It has been hypothesized that if recombination is variable among strains, selection should favor higher recombination rates among pathogens, as they face additional selection pressures from host defenses. To test this hypothesis we have developed a plasmid-based method for estimating the rate of recombination independently of other factors such as DNA transfer, selective processes, and mutational interference. Our results with 160 human commensal and extraintestinal pathogenic Escherichia coli (ExPEC) isolates show that the recombinant frequencies are extremely diverse (ranging 9 orders of magnitude) and plastic (they are profoundly affected by growth in urine, a condition commonly encountered by ExPEC). We find that the frequency of recombination is biased by strain lifestyle, as ExPEC isolates display strikingly higher recombination rates than their commensal counterparts. Furthermore, the presence of virulence factors is positively associated with higher recombination frequencies. These results suggest selection for high homologous recombination capacity, which may result in a higher evolvability for pathogens compared with commensals.


Subject(s)
Escherichia coli/genetics , Escherichia coli/pathogenicity , Homologous Recombination/genetics , Intestines/microbiology , Genes, Bacterial , Mutagenesis/genetics , Mutation Rate , Virulence/genetics
8.
Proc Natl Acad Sci U S A ; 111(19): E1960-9, 2014 May 13.
Article in English | MEDLINE | ID: mdl-24778234

ABSTRACT

CCR5 and CXCR4, the respective cell surface coreceptors of R5 and X4 HIV-1 strains, both form heterodimers with CD4, the principal HIV-1 receptor. Using several resonance energy transfer techniques, we determined that CD4, CXCR4, and CCR5 formed heterotrimers, and that CCR5 coexpression altered the conformation of both CXCR4/CXCR4 homodimers and CD4/CXCR4 heterodimers. As a result, binding of the HIV-1 envelope protein gp120IIIB to the CD4/CXCR4/CCR5 heterooligomer was negligible, and the gp120-induced cytoskeletal rearrangements necessary for HIV-1 entry were prevented. CCR5 reduced HIV-1 envelope-induced CD4/CXCR4-mediated cell-cell fusion. In nucleofected Jurkat CD4 cells and primary human CD4(+) T cells, CCR5 expression led to a reduction in X4 HIV-1 infectivity. These findings can help to understand why X4 HIV-1 strains infection affect T-cell types differently during AIDS development and indicate that receptor oligomerization might be a target for previously unidentified therapeutic approaches for AIDS intervention.


Subject(s)
CD4 Antigens/metabolism , HIV Envelope Protein gp120/metabolism , HIV Infections/metabolism , HIV-1/metabolism , Receptors, CCR5/metabolism , Receptors, CXCR4/metabolism , Actin Depolymerizing Factors/metabolism , CD4 Antigens/chemistry , Cell Fusion , Dimerization , Flow Cytometry , Fluorescence Resonance Energy Transfer , HEK293 Cells , Humans , Jurkat Cells , Lim Kinases/metabolism , Protein Binding/physiology , Protein Structure, Quaternary , Receptors, CCR5/chemistry , Receptors, CXCR4/chemistry , Th1 Cells/metabolism , Th1 Cells/virology , Th2 Cells/metabolism , Th2 Cells/virology
9.
Antimicrob Agents Chemother ; 56(5): 2767-9, 2012 May.
Article in English | MEDLINE | ID: mdl-22371901

ABSTRACT

To determine whether the overexpression of chromosomal genes can confer fosfomycin resistance, genomewide screening of a complete set of 5,272 plasmid-expressed open reading frames of Escherichia coli (ASKA collection) was performed. Major results are that (i) no clinical level of resistance is achieved by overexpressing chromosomal genes, except murA; (ii) this level is reached at a low fitness cost; and (iii) this cost is much lower than that imposed by other mutations conferring fosfomycin resistance.


Subject(s)
Alkyl and Aryl Transferases/genetics , Bacterial Proteins/genetics , Drug Resistance, Bacterial/genetics , Escherichia coli/genetics , Fosfomycin/pharmacology , Genome, Bacterial , Anti-Bacterial Agents/pharmacology , Biological Transport/drug effects , Escherichia coli/drug effects , Escherichia coli/growth & development , Escherichia coli Infections/drug therapy , Escherichia coli Infections/microbiology , Gene Expression , Gene Expression Profiling , Genetic Fitness , Humans , Microbial Sensitivity Tests , Mutation , Sequence Analysis, DNA
SELECTION OF CITATIONS
SEARCH DETAIL
...