Synergistic cranberry juice combinations with natural-borne antimicrobials for the eradication of uropathogenic Escherichia coli biofilm within a short time

Lett Appl Microbiol. 2019 Apr;68(4):321-328. doi: 10.1111/lam.13140. Epub 2019 Mar 13.


Urinary tract infections (UTI), one of the most common diseases in humans, are caused primarily by uropathogenic Escherichia coli (UPEC). Cranberry juice (CB) is a widely known prophylaxis for UTI, but the treatment of CB alone could not effectively eradicate preformed UPEC biofilms. The aim of this study was to develop enforced CB composites within a short time by adding a small quantity of natural borne antimicrobials. UPEC biofilms (initial: 6·0 log CFU per cm2 ), formed on silicone coupons in artificial urine medium, were exposed to CB (4-8%), caprylic acid (CAR; 0·025-0·05%) and thymol (TM; 0·025-0·05%) at 37°C for 1 min. Individual treatment of each compound did not show the significant antibacterial effect on UPEC biofilms (P > 0·05). Otherwise, the survivor counts of biofilms were synergistically reduced with CB containing any of the antimicrobials. For example combined treatment with CB (8%) + CAR (0·05%) + TM (0·05%) resulted in a 6 log reduction in UPEC populations in the biofilm (no detectable bacteria remained) with 4·6 log of synergistic bactericidal effect. The confocal laser scanning microscope images indicated that any composites including TM might result in biofilm detachment from the surface. The present method is cost-effective and more acceptable to consumers as it is based on the synergistic interaction of natural borne antimicrobials. The results of this study could be widely applicable in the functional food, medical and healthcare field. SIGNIFICANCE AND IMPACT OF THE STUDY: Anti-biofilm effect of cranberry juice (CB) has been focused mainly on inhibiting biofilm formation of uropathogenic Escherichia coli (UPEC); however, combined treatment with natural borne antimicrobials derived from coconut oil (caprylic acid) and oregano essential oil (thymol) could synergistically enhance its eradicating activity against biofilms. This study developed novel CB composites showing marked anti-biofilm effects (complete eradication of UPEC biofilms within just 1 min).

Keywords: biofilms; caprylic acid; cranberry; thymol; urinary tract infections; uropathogenic Escherichia coli.

MeSH terms

  • Anti-Bacterial Agents / pharmacology*
  • Biofilms / growth & development*
  • Caprylates / pharmacology*
  • Escherichia coli Infections / drug therapy
  • Fruit and Vegetable Juices
  • Humans
  • Microscopy, Confocal
  • Oils, Volatile / pharmacology
  • Plant Preparations / pharmacology*
  • Thymol / pharmacology*
  • Urinary Tract Infections / drug therapy
  • Urinary Tract Infections / microbiology
  • Uropathogenic Escherichia coli / drug effects*
  • Vaccinium macrocarpon / chemistry


  • Anti-Bacterial Agents
  • Caprylates
  • Oils, Volatile
  • Plant Preparations
  • Thymol
  • octanoic acid