Using Atomic Force Microscopy to Measure Anti-Adhesion Effects on Uropathogenic Bacteria, Observed in Urine after Cranberry Juice Consumption

Abstract

A volunteer was given cranberry juice cocktail (CJC) or water to drink, and urine was collected at 2 and 8 hours after consumption, in order to quantitatively determine whether adhesion forces were changed for the volunteer after CJC consumption. Atomic force microscopy (AFM) was used to measure adhesion forces between bacteria and a silicon nitride tip. Forces between Escherichia coli or Staphylococcus aureus and the AFM tip were lower in the urine after the volunteer consumed CJC, compared to drinking water. A steric model was applied to the AFM data, in order to quantify how the urine changed the properties of the bacterial surfaces. There was a small decrease in the equilibrium length of surface molecules on the bacteria when in the post-CJC urine, compared to the post-water urine. However, these changes were not statistically significant. We hypothesize that post-CJC urine imparts subtle changes on the molecules of the bacterial surfaces, and that these changes lead to the reduction in adhesion with the AFM probe.