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Contribution of oxidative damage to antimicrobial lethality
1Public Health Research Institute, New Jersey Medical School-UMDNJ, Newark, NJ 07103, USA.
Antimicrobial Agents and Chemotherapy
|February 19, 2009
Summary
Antimicrobial drugs generate hydroxyl radicals, increasing bacterial lethality. Targeting oxidative stress pathways could enhance the effectiveness of antibiotics like norfloxacin, ampicillin, and kanamycin.
Area of Science:
- Microbiology
- Biochemistry
- Molecular Biology
Background:
- Antimicrobial agents can induce oxidative stress in bacteria.
- The precise mechanisms by which oxidative stress contributes to antimicrobial lethality are not fully understood.
Purpose of the Study:
- To investigate the role of hydroxyl radicals in the lethality of antimicrobial drugs.
- To elucidate the pathway linking oxidative stress to bacterial killing by antibiotics.
Main Methods:
- Utilized mutational analysis in Escherichia coli, targeting genes involved in oxidative stress response (sodA, sodB, katG, ahpC).
- Employed chemical perturbations, including an iron chelator (bipyridyl) and a hydroxyl radical scavenger (thiourea).
- Assessed the lethal activity of norfloxacin, ampicillin, and kanamycin in wild-type and mutant strains.
Main Results:
- Norfloxacin lethality was reduced in double sodA/sodB mutants and increased in katG mutants, indicating roles for superoxide dismutation and peroxide detoxification.
- Iron chelators and hydroxyl radical scavengers decreased norfloxacin's lethal activity, implicating hydroxyl radicals generated via the Fenton reaction.
- Ampicillin and kanamycin showed similar patterns, with hyperlethality observed in an ahpC mutant.
Conclusions:
- Antimicrobial stress promotes superoxide production, leading to peroxide formation and subsequent generation of toxic hydroxyl radicals.
- Hydroxyl radicals significantly enhance the lethality of various antimicrobial agents, including fluoroquinolones and beta-lactams.
- Oxidative stress response pathways represent potential targets for potentiating antimicrobial efficacy.
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