The adhesion of pathogenic organisms to a tissue surface is required to initiate most infectious diseases (Sharon & Ofek 2002). Cranberry is a potent inhibitor of Escherichia coli adhesion, thereby influencing the initiation of disease without exerting bactericidal activity. One in vitro study found that cranberryjuice inhibited adhesion of 46 different E. coli isolates by 75% (Sobota 1984): when administered to mice for 14 days, adherence of E. coli to uroepithelial cells was inhibited by 80%. Significant inhibition of adherence was also observed in samples of human urine 1-3 hours after subjects drank a cranberry drink.
It appears that the anti-adhesion effects are a result of irreversible inhibition of the expression of P-fimbriae of E. coli (Ahuja et al 1998). Electron micrographie evidence Cranberry 324
suggests that cranberryjuice acts either on the cell wall, preventing proper © 2007 Elsevier Australia
attachment of the fimbrial subunits, or as a genetic control preventing the expression of normal fimbrial subunits, or both.
This inhibitory effect has not only been seen with E. coli and uroepithelial tissues, but also in the adhesion of Helicobacter pylori to human gastrointestinal cells (Burger et al 2002) and in the co-aggregation of oral bacteria and Streptococcus mutans counts in saliva (Sharon & Ofek 2002, Weiss et al 1998).
Earlier hypotheses that cranberry juice prevents UTI by acidification of urine or by its hippuric acid content have not been substantiated.
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