The Effects of Cranberry Juice on the Urinary Tract Infection Causing Bacteria Known as
Escherichia coli.
Shirin Moftakhar and Assal Parsa
Department of Biological Sciences
Saddleback College
Mission Viejo CA 92692
Previous clinical research has found that the consumption of cranberry products
can inhibit urinary tract infection by preventing the adhesion of Escherichia coli to
uroepithelial cells. The two main reasons theorized to contribute to the inhibition of UTI
are the fructose and an unknown polymeric compound found in cranberries. Investigators
are interested in testing the effects of cranberry juice on the urinary tract infection causing
bacteria, E. coli. Two experimental groups were tested, one was the cranberry juice and the
other fructose solution. Thirty samples of nutrient broth were inoculated with E. coli and
spread on thirty Petri dishes of nutrient agar. They were divided in three groups of ten
with each group containing chads dipped in cranberry juice for one group, fructose for the
other, and deionized water for the last. After they were incubated for 72 hours at 37°C, the
zones of inhibitions were measured. ANOVA yielded a change and a Bonferroni correction
test was ran. The results of the post hoc test indicated that cranberry juice and fructose
repectively had a significant effect on the inhibition of E. coli (p=0.0167)
Introduction
According to National Institutes of Health (NIH), the second most common type of
infection affecting women, the elderly, and infants are urinary tract infections (UTIs) meaning
one in three will have a UTI at least once in her lifetime. The presence of greater than 100,000
units/ml of bacteria in the urine exceeding a threshold value for significance can result in urinary
tract infection (UTI). Infection arises from bacterial growth within the usually sterile urinary
tract (Guay, 2009). There are two types of UTIs: Lower UTI and Upper UTI. Lower UTIs
involve only the bladder, whereas upper UTIs involve both the bladder and the kidneys
(pyelonephritis) (Jepson, 2004). Although the standard treatment for UTI is antibiotic therapy,
rising clinical failure rates of trimethoprim-sulfamethoxazole due to bacterial resistance has led
physicians in some areas of the country to consider prescribing fluoroquinolones as first-line
treatment (Howell, 2007). Because of these resistance building abilities, Pharmaceutical
companies are constantly working on the development of new antibiotics. In the meantime,
alternative therapies for prevention of UTI should be taken into consideration to slow down the
rate of antibiotic resistance development.
Cranberry juice (Vaccinium macrocarpon) has been used widely for many years to
prevent and treat urinary tract infections. There is positive clinical evidence that the consumption
of cranberry juice can decrease the number of symptomatic UTI’s based on two randomized
double-blind studies on women over a 12-month period (Avorn and Kontiokari). However, there
is no prior evidence that cranberry can treat UTI once an infection is present. Cranberry juice and
cranberry juice cocktail have been known to inhibit the adherence of bacteria such as E. coli to
host tissue (Zafriri, 1989). Another study also suggests that benefits of cranberry were due to its
acidity (Liu, 2008). Cranberries contain two compounds which inhibit adherence – fructose and a
polymeric compound of unknown nature (Jepson, 2004). Although many juices contain fructose,
only cranberries and blueberries contain the polymeric compound. Cranberry juice will create an
acidic state by lowering the pH; this acidic environment will kill and inhibit the growth of
bacteria. The purpose of this study is to determine if cranberry juice or fructose do inhibit the
growth of UTI by testing it on E. coli growth.
.
Methods and Materials
Nutrient Agar for culturing Escherichia coli was prepared on 4 November 2009 in the
biology lab at Saddleback College, Mission Viejo, CA. 15 ml of the nutrient agar was plated in
30 petri dishes using the aseptic technique. On 5 November 2009, 0.25 ml of E. coli was lawn
spread onto all 30 dishes. 20 ml of fructose with a 0.60 M concentration was prepared. 20 ml of
Kirkland Signature cranberry juice cocktail and deionized water were poured into two 100 ml
beakers. One hundred and eighty chads were made from Wattmans filter paper and autoclaved
for 2 hours. Two chads dipped in DI water were placed on each of the first 10 petri dishes as the
control group which makes n=20. Two chads dipped in a previously prepared fructose solution
were placed on the each of the 10 petri dishes in the second group. On each of the 10 petri dishes
in the last group, the chads were dipped in cranberry juice cocktail. All 30 petri dishes were
placed in the incubator for 72 hours at 37°C. On 11 November 2009, the petri dishes were
inspected and the zone of inhibition for each dish was measured in centimeters. All data were
transferred to Microsoft Excel 2007 where further statistical manipulations were preformed.
Since a change was found when ANOVA was run, a Bonferroni correction test was done to
compare the results within the groups.
Results
The DI water had E. coli growth on top of the chads therefore the zone of inhibition is
zero while the fructose and cranberry juice had no growth on the chads with a ring of no E. coli
around it. Then was a significant difference between all three groups. The greatest difference was
between the DI water and the cranberry juice while the least was between the fructose and
cranberry juice.
Figure 1. The Cranberry Juice had the highest adhesion rate with a mean of 1.265 cm. The
Fructose also had some adhesion with a mean of 1 cm. The DI water had an adhesions rate of 0.
The p-value found for the groups was 0.0167.
Discussion
Based on our results, it can be concluded that cranberry juice does inhibit E. coli growth
thus inhibiting/preventing urinary tract infection (UTI). The mean difference between the control
group and the experimental groups was at least 1 cm. While cranberry juice and fructose did
have signs of inhibition, the chads in the deionized water were completely covered in E. coli.
There was more of a difference between cranberry juice and the DI water then the fructose and
the DI water. This suggests that although cranberry juice was the main prohibitor, the fructose in
the cranberry juice has inhibitory factors as well. Zafiri et al. (1989) found that the fructose in
cranberry juice and cocktails inhibits the adherence of type 1 fimbriae of E. coli to the urinary
tract epithelial cells. He also found that there are two types of inhibitors in cranberry juice, a
nondialyzable and a dialyzable one. It was brought to his attention that the main inhibitor was the
dialyzable one. The finding that both cranberry juice cocktail and 5% fructose inhibited yeast
agglutination by purified type 1 fimbriae proves that the fimbriae are the target of inhibitory
action. The P fimbriated E.coli, was also inhibited by the cocktail. The reason they were only
inhibited by the cranberry juice, was that the inhibitor was nondialyzable, suggesting its high
molecular weight.
In Ahuja’s study it was seen that the growth of E. coli in cranberry rich agar inhibited the
attachment of the p receptor specific beads to the epithelial tissue. Until the chemical nature of
the inhibitor is discovered, it is not possible to speculate on the methods by which it binds to P
fimbriated E. coli surfaces. Therefore the possibility that the possibility that the nondialyzable
constituents may inhibit adherence mediated by adhesions other than P fimbriae cannot be
ignored. As stated in the introduction, it was suggested that cranberry juice cocktail may
primarily act as a preventive agent in urinary tract infection. So the possibility that the fructose is
abrosbed in the alimentary tract should be considered. Since cranberry juice has fructose levels
higher than the required amount necessary for type 1 fimbriated E. coli inhibition, it is
conceivable that the inhibitory levels of sugar are determined in the colon where most of the E.
coli is present. A study by Guay showed that antibiotic resistant P fimbriated E. coli lost the
ability to adhere to bladder cell receptors in humans who had consumed 240 ml of cranberry
juice cocktail. This suggests that consuming cranberry juice on a daily basis can not only prevent
UTI, but also slow the pace of antibiotic resistance development by reducing the need for
antibiotics. This strategy can be very helpful considering the increasing antibiotic resistance rates
due o over-use of antibiotics.
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