1. The second urine of the day was collected for each of the 3 participants in this study. The urine
samples were centrifuged at 5000 rpm for 5 mins and filtered through a 0.45 µm pore filter. 7 mL
of the filtered urine were aliquotted in 6 tubes, one for each organism to be tested. Bacterial
suspensions were prepared in sterile distilled water and adjusted to 1.0 OD600. Each tube of urine
was then inoculated with its respective bacterial suspension to reach an initial OD reading (T0
) of
about 0.1. The urine samples were allowed to incubate for 5 hours at 37℃ and then a second OD
reading (T5
) was taken to measure growth. To assess the bacterial growth inhibitory activity of
EGC present in the urine, the participants took a 225 mg EGCG supplement (Botanica Research)
and collected urine 2.5 to 3 hs after the treatment. The ability of the EGCG containing urine to
sustain growth was tested as explained above for the controls.
Abstract
Antimicrobial effects of green tea extract epigallocatechin
gallate (EGCG) on UTI-causing bacteria
Deronna John, Meiyi Wang, Robert Wu and Gloria Viboud
Methods and Results
Conclusion
Introduction
Discussion
Urinary tract infections are the second most common type
of infection leading to more than 8 million doctor visits in
the United States per year. The emergence of antibiotic
resistance is making treatment more challenging. Therefore,
it has become important to find alternative ways to treat and
prevent urinary tract infections.
In recent years, green tea has become more than just a
beverage and some researchers believe that it is able to
decrease the chances of getting various cancers, prevent
gum infections, prevent and treat wound infections and
inhibit bacterial growth. The polyphenols found in the plant
responsible for these benefits are epigallocatechin (EGC),
epicatechin gallate (ECG), and epigallocatechin gallate
(EGCG). EGCG has the most antimicrobial effects. Because
many of these polyphenols accumulate in urine, we
hypothesize that green tea’s polyphenols could inhibit
growth of the common UTI causing bacteria. Here, we
determined the antimicrobial effects of green tea and EGCG
on Escherichia coli, Staphylococcus species, Proteus and
Klebsiella by the Kirby Bauer method. In addition, we
measured the growth of uropathogenic bacteria in urine
before and after the consumption of a green tea extract
EGCG.
Several studies have shown that polyphenols found in
extracts of the Camellia sinensis leaves (green tea) can
inhibit growth of a wide range of microbes and have
synergistic effects with various antibiotics. Some of the
polyphenols, such as epigallocatechin (EGC) and
epigallocatechin gallate (EGCG), concentrate in urine
making them good potential candidates for the treatment or
prevention of UTI. In this study, the antimicrobial activity of
green tea extract on six common uropathogens, E.coli, K.
pneumoniae, S.aureus, S.epidermidis, and S.saprophyticus,
was investigated. In the disk diffusion assay, extracts from
different green tea brands and EGCG supplement inhibited
the growth of all organisms tested except for that of E.coli.
Urine samples collected 2.5 to 3hs after ingestion of 225mg
EGCG capsule showed an overall decrease of bacterial
growth when compared to control urine samples collected
from the same individuals with no ECGC treatment.
Although this is only a small pilot study, the results suggest
that EGCG treatment could be useful to prevent recurrent
UTIs.
Based on the in-vitro disk susceptibility test, bacterial
growth for all organisms was inhibited by the tea extracts
and the EGCG supplement except for Escherichia coli.
The green tea supplement EGCG provided the largest zone
of inhibition when compared to the green tea extracts (refer
to Figure 1). This is probably due to a higher concentration
of polyphenols present in the supplement. Interestingly,
green tea extracts have a larger zone of inhibition for gram
positive organisms when compared to gram negative,
which can be due to the antimicrobial mechanisms of the
catechins.
The ex-vivo study, in which 5 hour-bacterial growth was
compared in urine before and after consumption of EGCG,
showed that the EGCG supplement markedly inhibited
bacterial growth of S. saprprophyticus, S. epidermidis and
P. vulgaris. Less clear is the effect on S.aureus and K.
pneumoniae. Variation in the amount of bacterial growth in
urine occurred among participants and even on different
days within the same participant.
In conclusion, green tea extract catechins were able to
decrease or inhibit the growth of bacteria in the urine. This
experiment showed that the antimicrobial properties in the
green tea can decrease bacterial growth in both gram-
positive and gram-negative.
However, the majority of urinary tract infections are caused
by E. coli; and in our hands bacterial growth was
unaffected by the green tea and its extracts. Other
microorganisms affiliated with urinary tract infections,
such as S. saprprophyticus, S. epidermidis and P. vulgaris,
were considerably reduced. Although the population in this
study is small the results suggest that the antimicrobial
properties of green tea has the potential of preventing
urinary tract infections by inhibiting the growth of bacteria.
The antibacterial activity of 5 brands of green tea and an EGCG supplement was measured by the disk
susceptibility test. This was to test if the green tea and EGCG supplement can inhibit bacterial growth.
30mL of sterile water, per tea,
were boiled in beakers, allowed to
cool to ~80℃ before the tea bags
were placed into them and brewed
for 3 minutes. The supplement
capsule was broken and its contents
were poured into a separate beaker
of water as well. Filter paper disks were
dipped in the teas and supplement
solution. Mueller-Hinton plates were
streaked with 0.5 McFarland standard
bacterial suspensions of different bacterial strains. After 10 minutes, disks were placed onto each plate.
After 24hr incubation at 37℃, the zones of inhibition were measured and recorded as shown in the
table above. The different tea brands had comparable bacterial growth inhibitory activity, and overall
the EGCG extract had a slightly higher activity against most pathogens. Interestingly, no inhibitory
activity was displayed for E.coli growth by any of the green tea nor the EGCG supplement.
Figure 1: Zone of Inhibition Measurements (mm)
for Green Tea and EGCG Supplement
Haiku Celestial Bigelow Uncle Lee’s Lipton Supplement
P. vulgaris 15 7 15 18 17 18
K. pneumoniae 11 9 12 13 14 16
S. aureus 15.5 15 15 16 18 20.5
S. epidermidis 21 19.5 15 14 18 24.5
E. coli 0 0 0 0 0 0
S. saprophyticus 19 15 11 13 18 19
Bacteria Bact. OD T0 Control T0 With EGCG T5 Control T5 With EGCG
Average T0 OD Average T0 OD Average T5 Average T5 Average
S. saprophyticus 1.1 0.120 0.122 0.553 0.231
K. pneumoniae 1.035 0.129 0.126 0.299 0.256
S. epidermidis 1.061 0.118 0.118 0.557 0.237
P. vulgaris 1.055 0.117 0.123 0.485 0.234
S. aureus 1.046 0.126 0.117 0.300 0.265