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Published on: September 8, 2021
Ethylenediaminetetraacetic Acid Enhances Vancomycin and Reactive Oxygen Species-Mediated Killing of
Joshua Olson1, Anuj K Khetarpal2, Allen Jankeel2
1Department of Pediatrics, University of California, San Diego School of Medicine, La Jolla, California, USA.
Background:
The emergence of antibiotic-tolerant staphylococcal strains, such as vancomycin-intermediate Staphylococcus aureus (VISA), poses a significant healthcare challenge and complicates treatment regimens. VISA often exhibits mutations in Krebs cycle enzymes, promoting anaerobic metabolism under physiological conditions and reducing susceptibility to antibiotics and innate immune defenses-factors not typically captured in standard susceptibility testing. Building on these findings, we investigated ethylenediaminetetraacetic acid (EDTA), a chelator that enhances reactive oxygen species (ROS) production, as an adjunct to vancomycin for combating VISA infections.
Methods:
RNA sequencing analysis compared gene expression of a well-characterized VISA strain (D712) under physiological versus nutrient-rich conditions. Hydrogen peroxide (H2O2) killing assays were conducted with and without the hydroxyl radical quencher thiourea, while neutrophil killing assays used ROS scavenger butylated hydroxyanisole (BHA). A murine bacteremia model assessed the effects of vancomycin, EDTA, or their combination on VISA.
Results:
VISA exhibited downregulation of Krebs cycle enzymes and other genes associated with resistance to iron and ROS-mediated killing under physiological conditions. EDTA, alone or with vancomycin, improved H2O2-mediated killing compared to vancomycin alone, a response counteracted by thiourea. The combination of EDTA and vancomycin enhanced neutrophil killing of VISA more effectively than either treatment alone, an effect negated by BHA. In vivo, EDTA enhanced vancomycin activity against VISA.
Conclusions:
EDTA potentiates vancomycin efficacy against VISA in vivo and enhances susceptibility to H2O2 and neutrophil killing. Reduced expression of Krebs cycle enzymes in VISA suggests that EDTA promotes ROS-mediated bacterial killing, targeting a key mechanism by which persistent staphylococci evade host defenses.
Insights
Ethylenediaminetetraacetic acid (EDTA) enhances vancomycin effectiveness against antibiotic-tolerant Staphylococcus aureus (VISA). This combination boosts bacterial susceptibility to reactive oxygen species and neutrophil defenses, offering a new strategy for treating persistent infections.
Area of Science:
- Microbiology
- Infectious Diseases
- Pharmacology
Background:
- Vancomycin-intermediate Staphylococcus aureus (VISA) presents a major clinical challenge due to reduced susceptibility to antibiotics.
- VISA strains often display altered metabolism, including downregulated Krebs cycle enzymes, contributing to tolerance and evasion of immune defenses.
- Standard susceptibility testing may not capture these tolerance mechanisms, necessitating novel therapeutic approaches.
Purpose of the Study:
- To investigate ethylenediaminetetraacetic acid (EDTA) as an adjunct to vancomycin for combating VISA infections.
- To determine if EDTA enhances vancomycin's efficacy by increasing bacterial susceptibility to reactive oxygen species (ROS) and innate immune cells.
Main Methods:
- Gene expression analysis (RNA sequencing) of VISA under different conditions.
- In vitro killing assays using hydrogen peroxide (H2O2) and human neutrophils, with and without ROS scavengers.
- In vivo assessment in a murine bacteremia model to evaluate vancomycin and EDTA combination therapy.
Main Results:
- VISA strains showed reduced expression of Krebs cycle enzymes under physiological conditions.
- EDTA, with or without vancomycin, improved bacterial killing by H2O2 and neutrophils, an effect dependent on ROS.
- In a mouse model, EDTA potentiated vancomycin's activity against VISA.
Conclusions:
- EDTA enhances vancomycin efficacy against VISA both in vitro and in vivo.
- EDTA likely promotes ROS-mediated bacterial killing by targeting metabolic adaptations in VISA.
- This study highlights EDTA as a promising adjunct therapy to overcome vancomycin tolerance in Staphylococcus aureus infections.
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