The use of 4-Hexylresorcinol as antibiotic adjuvant

PLoS One. 2020 Sep 22;15(9):e0239147. doi: 10.1371/journal.pone.0239147. eCollection 2020.

Abstract

Ever decreasing efficiency of antibiotic treatment due to growing antibiotic resistance of pathogenic bacteria is a critical issue in clinical practice. The two generally accepted major approaches to this problem are the search for new antibiotics and the development of antibiotic adjuvants to enhance the antimicrobial activity of known compounds. It was therefore the aim of the present study to test whether alkylresorcinols, a class of phenolic lipids, can be used as adjuvants to potentiate the effect of various classes of antibiotics. Alkylresorcinols were combined with 12 clinically used antibiotics. Growth-inhibiting activity against a broad range of pro- and eukaryotic microorganisms was determined. Test organisms did comprise 10 bacterial and 2 fungal collection strains, including E. coli and S. aureus, and clinical isolates of K. pneumoniae. The highest adjuvant activity was observed in the case of 4-hexylresorcinol (4-HR), a natural compound found in plants with antimicrobial activity. 50% of the minimal inhibitory concentration (MIC) of 4-HR caused an up to 50-fold decrease in the MIC of antibiotics of various classes. Application of 4-HR as an adjuvant revealed its efficiency against germination of bacterial dormant forms (spores) and prevented formation of antibiotic-tolerant persister cells. Using an in vivo mouse model of K. pneumoniae-induced sepsis, we could demonstrate that the combination of 4-HR and polymyxin was highly effective. 75% of animals were free of infection after treatment as compared to none of the animals receiving the antibiotic alone. We conclude that alkylresorcinols such as 4-HR can be used as an adjuvant to increase the efficiency of several known antibiotics. We suggest that by this approach the risk for development of genetically determined antibiotic resistance can be minimized due to the multimodal mode of action of 4-HR.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adjuvants, Pharmaceutic / pharmacology*
  • Adjuvants, Pharmaceutic / therapeutic use
  • Animals
  • Anti-Bacterial Agents / pharmacology*
  • Anti-Bacterial Agents / therapeutic use
  • Disease Models, Animal
  • Drug Resistance, Multiple, Bacterial
  • Drug Synergism
  • Drug Therapy, Combination / methods
  • Escherichia coli / drug effects
  • Female
  • Hexylresorcinol / pharmacology*
  • Hexylresorcinol / therapeutic use
  • Humans
  • Klebsiella Infections / drug therapy*
  • Klebsiella Infections / microbiology
  • Klebsiella pneumoniae / drug effects
  • Klebsiella pneumoniae / isolation & purification
  • Mice
  • Microbial Sensitivity Tests
  • Polymyxins / pharmacology
  • Polymyxins / therapeutic use
  • Sepsis / drug therapy*
  • Sepsis / microbiology
  • Staphylococcus aureus / drug effects

Substances

  • Adjuvants, Pharmaceutic
  • Anti-Bacterial Agents
  • Polymyxins
  • Hexylresorcinol

Grants and funding

This work was supported by internal funding from the Russian Academy of Sciences and the University of Basel. JB and JH were supported by the Swiss National Science Foundation (SNF grant No. 173057).