Cranberry products are a nonantimicrobial
method for prevention of urinary tract infection
(UTI). Cranberry proanthocyanidin (PAC), a type of condensed tannin, is the active ingredient in cranberry that
inhibits adherence of P-fimbriated Escherichia coli to
uroepithelial cells. Previous cranberry studies for UTI
prevention yielded conflicting results, probably because
of variability of PAC dose and clinical populations studied. In a clinical trial of 300 mL of cranberry juice beverage daily (36 mg PAC), older women (mean age 78.5) had 58% lower odds of having bacteriuria and pyuria than controls, but nursing home residents have difficulty ingesting the volume of juice necessary to prevent bacteriuria. Cranberry capsules are feasible to administer to nursing home residents, but their efficacy has not been demonstrated. In vitro, 36–108 mg of PAC is efficacious at inhibiting bacterial adherence to uroepithelial cells, but the most efficacious dose for older nursing home residents has not been identified. The goal of this study was to identify the optimal dose of cranberry capsules that reduced the incidence of bacteriuria plus pyuria over 1 month.