Investigating the inhibitory effects of cranberry juice metabolites on uropathogenic Escherichia coli for the prevention of urinary tract infections Public

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Regular ingestion of American cranberry (Vaccinium macrocarpon) has been traditionally utilized for its health benefits against urinary tract infections. The proanthocyanidins (PACs), in particular, the unique A-type double linkages of PACs present in cranberry, have been identified as the active components. However, A-type PACs and any other active agents have not yet been detected or identified in urine. Additional experiments are required to investigate the inhibitory effects and persistence of cranberry metabolites present in urine collected following CJC consumption, and to determine how these compounds act against uropathogenic Escherichia coli for the prevention of urinary tract infections. Two separate bioassays (a biofilm formation assay and a bacterial cell viability assay) were used to determine the in vitro effect of cranberry juice cocktail (CJC) oral consumption on bacterial anti-adhesion activity in a double-blind, placebo-controlled pilot clinical trial. A single dose of 16 oz. of CJC or a placebo beverage was given to ten healthy women, ages ranging from 18 to 27, and urine samples were collected in the following 48 hours. A washout period of seven days was allowed. Bacteria (Escherichia coli B37, CFT073, BF1023, HB101, and Staphylococcus aureus ATCC43866) were cultured in the urine samples, supplemented with media, and the amount of biofilm formed was measured using a crystal violet absorbance assay in a 96-well plate. In the urine of volunteers who had consumed CJC, biofilm formation was inhibited within 24 hours after CJC consumption, and started to increase after 48 hours by 49-67%. S. aureus showed the least biofilm formation after incubation with post-CJC urine. The results indicated that drinking CJC can be an effective preventive measure for bacterial adhesion and biofilm formation in healthy women. The anti-biofilm activity peaks between 24 and 48 hours after drinking CJC. The viability assay showed that the colony count after culturing in urine collected following consumption of CJC or placebo were not significantly different, implying that CJC works as an inhibitor by blocking bacterial adhesion instead of killing the bacteria or restraining its growth. Another randomized, placebo-controlled, double-blind, crossover study was conducted to further investigate the molecular-scale effect of cranberry juice metabolites on two P-fimbriated E. coli strains: B37 and CFT 073, as assessed by atomic force microscopy (AFM). Three female subjects were asked to consume 8 oz. CJC or water. The washout period was 7 days. The urine samples were collected at 2, 4 and 6 hours post-ingestion of CJC or water. Urine collected before consumption of CJC was used as a control. For this control urine, the average adhesion force between E. coli and uroepithelial cells was 13.09 ± 11.60 nN for CFT073 and 10.30 ± 5.50 nN for B37. For post-CJC urine treatment, the adhesion forces decreased to 2.94 ± 1.82 nN at 2 hours after consumption then increased slightly to 5.51 ± 2.78 nN at 6 hours after ingestion for CFT073, while they decreased to 4.77 ± 3.33 nN after consuming for 2 hours and seemed to be stable in the next 4 hours following consumption (5.52 ± 4.04 nN after drinking for 4 hours; 5.05 ± 4.42 nN after drinking for 6 hours) for B37. The adhesion forces in post-water consumption urine were similar to those of the background for E. coli B37; meanwhile a downward trend for the adhesion forces in post-water consumption urine compared to the background was observed for E. coli CFT073. However, these adhesion forces in post-water consumption urine were still higher than those measured after CJC consumption at the same time intervals. The mean differences between the cranberry and placebo groups were statistically different according to the two way ANOVA procedure followed by Holm-Sidak test. Our results suggest a significant inhibitory interaction between the daily consumption of 8 oz. cranberry juice and bacterial adhesive activity. These results help form the mechanistic understanding of how cranberry products can be used to prevent bacterial attachment to host tissue, and may lead to new therapeutic strategies to prevent the rising problem of bacteria antibiotic resistance.

  • English
  • etd-082111-202623
Defense date
  • 2011
Date created
  • 2011-08-21
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