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Green tea inhibits Helicobacter growth in vivo and in vitro

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Abstract

Helicobacter infection, one of the most common bacterial infections in man worldwide, is a type 1 carcinogen and the most important risk factor for gastric cancer. Helicobacter pylori bacterial factors, components of the host genetics and immune response, dietary cofactors and decreased acid secretion resulting in bacterial overgrowth are all considered important factors for induction of gastric cancer. Components found in green tea have been shown to inhibit bacterial growth, including the growth of Helicobacter spp. In this study, we assessed the bactericidal and/or bacteriostatic effect of green tea against Helicobacter felis and H. pylori in vitro and evaluated the effects of green tea on the development of Helicobacter-induced gastritis in an animal model. Our data clearly demonstrate profound growth effects of green tea against Helicobacter and, importantly, demonstrate that green tea consumption can prevent gastric mucosal inflammation if ingested prior to exposure to Helicobacter infection. Research in the area of natural food compounds and their effects on various disease states has gained increased acceptance in the past several years. Components within natural remedies such as green tea could be further used for prevention and treatment of Helicobacter-induced gastritis in humans.

Introduction

Helicobacter pylori is one of the most common chronic bacterial infections in man [1], [2], [3]. Following the discovery of the linkage between gastric adenocarcinoma and H. pylori infection, antibiotic therapy became an important tool in Helicobacter eradication. However, the wide abuse of antibiotics by the modern world has raised a new problem in medicine, namely antibiotic resistance. Helicobacter pylori resistance to metronidazole has been estimated to approach 60–70% in areas of high antibiotic use, and resistance to macrolides such as clarithromycin is also rising. The search for new chemical compounds with bactericidal or bacteriostatic effects against H. pylori is a challenge for the world's medical and scientific communities. Different dietary components have been shown to influence the outcome of Helicobacter infection [4], [5], [6], [7]. While components of green tea have been suggested to have anti-H. pylori effects in vitro, in vivo correlation is sparse. Interestingly, the combination of the main component of green tea (catechins) and sucralfate has a bactericidal effect on H. pylori infection in Mongolian gerbils [8], and green tea catechins may inhibit the H. pylori urease [9].

Tea is considered one of the most popular beverages in the world, especially in China and Japan. Tea extracts such as catechins inhibit the growth of Staphylococcus aureus, Staphylococcus epidermidis, Vibrio cholerae O1, V. cholerae non-O1, Vibrio parahaemolyticus, Vibrio mimicus, Campylobacter jejuni and Plesiomonas shigelloides in vitro [10] and have antibacterial and bactericidal activity against meticillin-resistant S. aureus (MRSA) in vitro [11]. The importance of green tea and its components has been reviewed by Hamilton-Miller [12]. In the present study, we evaluated the bactericidal and/or bacteriostatic effect of green tea on Helicobacter felis and H. pylori and showed that green tea, in an amount that could be clinically consumed, has bactericidal and bacteriostatic effects in vitro. In vivo studies demonstrated that consumption of green tea when taken before infection prevents gastric mucosal inflammation, and when taken after infection is established diminishes the magnitude of gastritis.

Section snippets

Animals

Six-week-old male C57BL/6J mice (Jackson Laboratories, Bar Harbor, ME) were housed in microisolator cages under specific pathogen-free conditions, fed standard chow and allowed free access to water and/or green tea as described below. Helicobacter felis and H. pylori bacteria were grown, enumerated and diluted with culture medium and a 500 μL total volume with 5 × 107 colony-forming units (CFU) was given by oral gavage three times at 2-day intervals to establish infection.

Preparation of green tea extracts

Three grams of dry green

Green tea is bacteriostatic against Helicobacter pylori and Helicobacter felis

Green tea-embedded discs (pH 7.0) were placed on bacterial plates shortly after bacteria were seeded and liquid was absorbed. Plates were incubated for 48 h. Control discs were embedded with alcohol (vehicle, pH 7.0) only. Green tea had a significant bacteriostatic effect on H. felis and H. pylori (Fig. 1A) (P < 0.05). The difference between the bacteriostatic effect of green tea on H. felis compared with H. pylori was not significant (P > 0.05).

Green tea has a bactericidal effect on actively growing Helicobacter felis and Helicobacter pylori

Bacterial plates were seeded with bacteria and grown

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