Related Experiment Video

Updated: Jul 19, 2026

Amikacin Protection Assay for Quantification and Visualization of Escherichia coli Cell Invasion
09:22

Amikacin Protection Assay for Quantification and Visualization of Escherichia coli Cell Invasion

Published on: July 3, 2026

Acquired gentamicin resistance by permeability impairment in Enterococcus faecalis

Elisabeth Aslangul1, Laurent Massias, Alain Meulemans

  • 1EA 3964, Faculté de Médecine de l'Université Paris 7, 46, rue Henri Huchard, 75870 Paris Cedex 18, France. elisabeth.aslangul@htd.aphp.fr

Antimicrobial Agents and Chemotherapy
|October 27, 2006
PubMed

Insights

This study investigated gentamicin resistance in Enterococcus faecalis. Researchers found impaired gentamicin uptake, not enzyme modification or efflux, contributes to this resistance, offering new insights into antibiotic resistance mechanisms.

Area of Science:

  • Microbiology
  • Molecular Biology
  • Antimicrobial Resistance

Background:

  • Enterococci exhibit intrinsic resistance to low aminoglycoside levels.
  • Previous studies identified Enterococcus faecalis with intermediate gentamicin resistance.
  • Synergism with cell-wall-active agents was maintained in previously selected mutants.

Purpose of the Study:

  • To elucidate the resistance mechanism of a high-level gentamicin-resistant Enterococcus faecalis mutant (1688-G3).
  • To investigate potential genetic mutations, enzyme activity, efflux pumps, and drug accumulation in the resistant strain.

Main Methods:

  • Genomic analysis for mutations in ribosomal protein L6 and 16S rRNA genes.
  • Phenotypic screening for aminoglycoside-modifying enzymes and efflux pump activity using ethidium bromide and pump inhibitors.
  • Development and application of a fluorescent polarization immunoassay to quantify gentamicin accumulation.
  • Assessment of FoF1-ATPase activity using N,N'-dicyclohexylcarbodiimide (DCCD) and analysis of atp gene expression.

Main Results:

  • No mutations were found in L6 ribosomal protein or 16S rRNA genes.
  • Aminoglycoside-modifying enzymes and efflux pumps were ruled out as primary resistance mechanisms.
  • Gentamicin accumulation was significantly impaired in the 1688-G3 mutant compared to the wild-type strain.
  • Impaired accumulation was partially reversible by DCCD, suggesting a potential role for the FoF1-ATPase, though its structural genes showed no mutations.

Conclusions:

  • The primary mechanism for high-level gentamicin resistance in this Enterococcus faecalis mutant is impaired gentamicin uptake.
  • Alterations in cellular processes, potentially related to the FoF1-ATPase, contribute to reduced drug accumulation.
  • Findings highlight uptake impairment as a novel mechanism for aminoglycoside resistance in enterococci.

More Related Videos

Characterizing Multidrug Efflux Systems in Acinetobacter baumannii Using an Efflux-Deficient Bacterial Strain and a Single-Copy Gene Expression System05:06

Characterizing Multidrug Efflux Systems in Acinetobacter baumannii Using an Efflux-Deficient Bacterial Strain and a Single-Copy Gene Expression System

Published on: January 5, 2024

Related Concept Videos

Development of Antibiotic Resistance01:30

Development of Antibiotic Resistance

Antibiotic resistance is a major public health concern that arises when bacteria evolve mechanisms to withstand the effects of antibiotic treatments. This resistance can be intrinsic, acquired through genetic mutations, or transferred between bacteria via horizontal gene transfer. The development of antibiotic resistance poses significant challenges in treating bacterial infections and necessitates ongoing research to develop new therapeutic strategies.Intrinsic resistance occurs when bacterial...
Mechanism of Antibiotic Resistance in MRSA01:25

Mechanism of Antibiotic Resistance in MRSA

Antibiotic resistance in bacteria arises when microorganisms evolve the ability to withstand drugs designed to kill them or inhibit their growth, rendering once-effective treatments useless. This phenomenon, driven by genetic change and selection under antibiotic exposure, poses a profound threat to modern medicine. Mechanisms include drug-inactivating enzymes (e.g., β-lactamases), efflux pumps that eject antibiotics, mutations altering antibiotic targets, decreased drug uptake, and acquisition...
Clinical Significance of Antibiotic Resistance01:25

Clinical Significance of Antibiotic Resistance

Methicillin-resistant Staphylococcus aureus (MRSA) presents a critical public health threat, arising from its capacity to resist β-lactam antibiotics due to acquisition of the mecA gene within the staphylococcal cassette chromosome mec (SCCmec). This gene encodes penicillin-binding protein 2a (PBP2a), which impairs binding efficacy of methicillin and other β-lactams. MRSA has evolved into distinct clonal lineages impacting humans and animals alike, reinforcing its significance within the One...
Determination of Multiple Dosing Parameters: Steady-State, Minimum and Maximum Concentrations01:15

Determination of Multiple Dosing Parameters: Steady-State, Minimum and Maximum Concentrations

Gentamicin, an aminoglycoside antibiotic, is commonly administered via intermittent intravenous infusion to treat severe infections. An intermittent one-hour infusion of gentamicin, administered at eight-hour intervals, allows for precise control of plasma drug concentrations, minimizing toxicity while ensuring therapeutic efficacy. Pharmacokinetic principles govern the dynamics of plasma concentrations and can be mathematically described using specific equations.The plasma drug concentration...
Estimation of k and VD of Aminoglycosides01:20

Estimation of k and VD of Aminoglycosides

Aminoglycosides are a class of antibiotics used to treat various bacterial infections. Clinicians must determine the elimination rate constant (k) and volume of distribution (VD) to optimize therapeutic efficacy and minimize toxicity. The k value represents the rate at which the drug is removed from the body, and the VD reflects the degree to which the drug distributes into body tissues. Accurately estimating these parameters allows healthcare professionals to tailor drug dosing to individual...
Inhibitors of Bacterial Protein Synthesis01:25

Inhibitors of Bacterial Protein Synthesis

Aminoglycosides constitute a highly potent class of bactericidal antibiotics that exert their antimicrobial effects by targeting the bacterial ribosome, specifically disrupting protein synthesis. These polycationic molecules consist of amino-modified sugars linked via glycosidic bonds to an aminocyclitol core such as 2-deoxystreptamine or streptamine. Their strong positive charges facilitate tight binding to the negatively charged phosphate backbone of ribosomal RNA (rRNA), primarily at the 16S...