Objective

In the United States, urinary tract infections are one of the most common bacterial infections, affecting 8 million people per year. Approximately 50% of women will develop a urinary tract infection during their lifetime. In 2000, the United States spent $2.14 billion toward UTI treatment. Urinary tract infections are generally considered easily treatable, with the majority of patients prescribed a regimen of antibiotics. Overuse of antibiotic therapy has burdened the clinical management of urinary tract infections, which has led to the increasing prevalence of antibiotic resistance. An alternative prophylactic is needed to combat the emergence of ineffective treatments. Cranberry may be beneficial in preventing recurrent urinary tract infections in certain at-risk populations.

The mechanism of action of cranberry was initially thought to be due to the fruit’s acidity, producing a bacteriostatic effect in the urine. More recently it was found that components in cranberry called proanthocyanidins, condensed tannin molecules with A-type linkages, exhibit potent bacterial antiadhesion activity. Herbals, such as cranberry, are not required to undergo the same rigorous testing to establish efficacy, dosage and safety as pharmaceutical agents regulated by the Food and Drug Administration. We sought to measure the bacterial anti-adhesion activity and proanthocyanidin levels in 7 commercially available cranberry supplements.

Study Design

The bioactivity of the 7 cranberry supplements in preventing adhesion of uropathogenic P-fimbriated Escherichia coli was tested by measuring the ability of the supplements to suppress agglutination of human red blood cells (A1, Rh+) following incubation with the bacteria. Endpoint concentrations were compared among the cranberry products, with the lowest concentration representing the highest bacterial antiadhesion activity. Wells containing bacteria plus phosphate-buffered saline, human red blood cells plus phosphate-buffered saline, bacteria plus test fraction, and human red blood cells plus test fraction served as negative controls for agglutination, and wells containing bacteria plus human red blood cells served as a positive control for agglutination.

Study Design

The bioactivity of the 7 cranberry supplements in preventing adhesion of uropathogenic P-fimbriated Escherichia coli was tested by measuring the ability of the supplements to suppress agglutination of human red blood cells (A1, Rh+) following incubation with the bacteria. Endpoint concentrations were compared among the cranberry products, with the lowest concentration representing the highest bacterial antiadhesion activity. Wells containing bacteria plus phosphate-buffered saline, human red blood cells plus phosphate-buffered saline, bacteria plus test fraction, and human red blood cells plus test fraction served as negative controls for agglutination, and wells containing bacteria plus human red blood cells served as a positive control for agglutination.