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 bacteriaDeronna 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 bagswere placed into them and brewed for 3 minutes. The supplementcapsule was broken and its contentswere poured into a separate beaker of water as well. Filter paper disks weredipped in the teas and supplementsolution. Mueller-Hinton plates werestreaked 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 EGCGAverage 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 0.256S. epidermidis 1.061 0.118 0.118 0.557 0.237P. vulgaris 1.055 0.117 0.123 0.485 0.234S. aureus 1.046 0.126 0.117 0.300 0.265