Medicinal plant extracts variously modulate susceptibility of Escherichia coli to different antibiotics

Microbiol Res. 2014 Apr;169(4):307-13. doi: 10.1016/j.micres.2013.06.013. Epub 2013 Jul 31.

Abstract

Antioxidant activity of green and black tea and extracts of medicinal plants and their ability to modulate antibiotic susceptibility in Escherichia coli were studied. Among a number of extracts tested the maximal capacity to scavenge DPPH radicals and chelate iron in chemical tests was found in green and black tea, Arctostaphylos uva-ursi and Vaccinium vitis-idaea. These extracts contained high level of polyphenols and in aerobic conditions exhibited prooxidant features, producing H2O2 and inducing expression of the katG gene encoding catalase HPI in E. coli cells. A good correlation between the polyphenol content and the ability of extracts to protect bacteria against peroxide stress was observed (r = 0.88). Polyphenol-rich extracts and iron chelators demonstrated the highest modulating effect on the antibiotic susceptibility by changing the time period before lysis started and by influencing the colony-forming ability of bacteria. The direction of the modulating effect was dependent on nature of antibiotic applied: under treatment with ciprofloxacin and ampicillin the extracts predominantly provided protective effects, while under treatment with kanamycin a bactericidal action was enhanced. Mechanism of modulating action of extracts on bacterial antibiotic susceptibility probably involves antioxidant, preferentially iron-chelating, or prooxidant properties of polyphenols.

Keywords: Antibiotics; Bacteria; Medicinal plant extracts; Oxidative stress.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Anti-Bacterial Agents / isolation & purification
  • Anti-Bacterial Agents / pharmacology*
  • Arctostaphylos / chemistry*
  • Biphenyl Compounds / metabolism
  • Chelating Agents / isolation & purification
  • Chelating Agents / pharmacology
  • Drug Antagonism
  • Drug Synergism*
  • Escherichia coli / drug effects*
  • Free Radicals / metabolism
  • Microbial Sensitivity Tests
  • Picrates / metabolism
  • Plant Extracts / isolation & purification
  • Plant Extracts / pharmacology*
  • Plants, Medicinal / chemistry*
  • Polyphenols / isolation & purification
  • Polyphenols / pharmacology
  • Vaccinium vitis-idaea / chemistry*

Substances

  • Anti-Bacterial Agents
  • Biphenyl Compounds
  • Chelating Agents
  • Free Radicals
  • Picrates
  • Plant Extracts
  • Polyphenols
  • 1,1-diphenyl-2-picrylhydrazyl