Because previous studies have shown that a high molecular mass constituent of cranberry juice inhibited adhesion of Escherichia coli to epithelial cells and coaggregation of oral bacteria, we have examined its effect on the adhesion of Helicobacter pylori to immobilized human mucus and to erythrocytes. We employed three strains of H. pylori all of which bound to the mucus and agglutinated human erythrocytes via a sialic acid-specific adhesin. The results showed that a high molecular mass constituent derived from cranberry juice inhibits the sialic acid-specific adhesion of H. pylori to human gastric mucus and to human erythrocytes.

In the 20th century, the health benefit most often attributed to the cranberry is its role in maintaining urinary-tract health. A 1998 study by the International Food Information Council (personal communication) indicated that 47% of consumers surveyed were aware of a link between cranberry juice and urinary-tract health.

Twenty-one female and 19 male subjects who had normal physical and laboratory examinations were randomly assigned into four groups of 10 subjects each. Each group was then randomly assigned a number (150, 180, 210, 240) which determined the amount of cranberry juice, in milliliters, members of that group would ingest with each meal during the experimental phase of the study. The study took place over a 12-day period. A one-group before-and-after design was used, with each subject serving as his or her own control. Diet was controlled; menus on days 1 through 6 were repeated on days 7 through 12 with the addition of cranberry juice at each meal. Subjects used nitrazine pH tape to measure the pH of midstream urine at each voiding. There were significant (.01 level) differences in mean urinary pH between each control group and its corresponding experimental group. Anticipated problems with increased number of bowel movements, weight gain, increased voiding frequency, and subject pH measurement inaccuracy did not occur.

Most research suggests that ingestion of cranberry juice may be useful in preventing urinary tract infections. This pilot study examines the effect of drinking moderate amounts of commercially available cranberry juice cocktail on urinary pH in older, institutionalized adults. The results of the study have implications for home care nurses who have similar patients in their case loads.

The purpose of this study was to quantitate the effect of cranberry juice ingestion on urinary acidification and calcium excretion, in a diet-controlled situation.

The influence of diet on aryl acid metabolism was determined in normal and azotemic subjects. Aryl acid content of serum and urine was estimated by fluorometry in relation to hippuric acid as a standard (FI-Hipp). Secretory activity, a reflection of the biological potency of aromatic acids in serum and urine, was determined by bioassay. The urinary excretion of FI-Hipp and secretory activity of five normal persons on an ad lib diet was 0.78 and 2.25 mM/day, respectively; similar values were observed in two subjects with chronic renal insufficiency. Subjects were fed prunes and cranberries, since these foods contain abundant quantities of hippurate precursors. Prunes 1.5 g/kg body weight, caused the urinary excretion of both FI-Hipp and secretory activity to increase about tenfold in normal and azotemic subjects. Prune feeding caused the serum levels of FI-Hipp and secretory activity to increase about threefold. Cranberries increased the renal excretion of FI-Hipp and secretory activity as did the ingestion of a beverage containing benzoate as a preservative. On the basis of these studies it is clear that diet is an important determinant of the load of aryl acids for urinary excretion; in patients with renal insufficiency the ingestion of foods containing precursors may cause serum level of biologically active aryl acids to increase strikingly.

Bacterial surface properties, such as electrostatic potential play an important role in the bacterial adhesion process, which is widely considered as the first step leading to infections. Cranberry juice and its compound A-type proanthocyanidins (PACs) were used to treat two isogenic E. coli strains and human uroepithelial cells and the zeta potentials were measured at several cranberry juice or PACs concentrations. P fimbriae were shown to be slightly positively charged, which helps bacteria adhere onto mammalian cells. PACs significantly decreased the bacterial zeta potentials from -15.6 ± 0.9 mV to -41.5 ± 0.7 mV, which increased the electrostatic repulsion forces to mammalian cells. Cranberry juice treatment did not change bacterial zeta potentials significantly, ranging from -14.9 ± 1.8 mV to -16.3 ± 0.8 mV. The abundance of other compounds in cranberry juice may have blocked the influence of PACs, considering the relatively small proportion of PACs in cranberry juice.

An extract from fresh cranberries was shown to decrease the strength of attachment of Escherichia coli to glass coverslips when incubated together for 2 h. Pre-conditioning of the surface prior to biofilm formation also significantly weakened the strength of attached cells.

BACKGROUND: The inhibition of Escherichia coli growth in the presence of Vaccinium macrocarpon has been extensively described; however, the mechanisms of this activity are not well characterized.

FINDINGS: Here, E. coli was grown in media spiked with cranberry juice. The growth rate and media pH were monitored over more than 300 generations. The pH of the growth media was found to decrease during cell growth. This result was unique to media spiked with cranberry juice and was not reproduced through the addition of sugars, proanthocyanidins, or metal chelators to growth media.

CONCLUSION: This study demonstrated that factors other than sugars or proanthocyanidins in cranberry juice result in acidification of the growth media. Further studies are necessary for a complete understanding of the antimicrobial activity of cranberry products.

An ethanolic extract of Cranberry exerted a significant antimicrobial effect on Saccharomyces bayanus and Pseudomonas fluorescens. The antimicrobial properties of cranberries were due to a number of factors. First, the low pH (2.6) inhibited many microorganisms per se, and its effect on the dissociation of benzoic acid made the inhibition more drastic. Secondly, after raising the pH to 5.2, cranberry juice still did not support the growth of S. bayanus. Growth did occur at pH 5.2 after 0.3% yeast nitrogen base was added. Thirdly, proanthocyanidins and flavonols were found to be the major microbial inhibitors other than benzoic acid. The results showed that proanthocyanidins provided 21.3% of the inhibition, the flavonols 18.5% and benzoic acid 15.6%.