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The inhibitory effects of black and green teas (Camellia sinensis) on growth of pathogenic Escherichia coli in vitro
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N Khalaji   , T Neyestani * |
| , tneyestani@nnftri.ac.ir |
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Abstract: (12596 Views) |
| Background and Objectives: The antimicrobial effects of green tea have been shown in many studies. However, there are not any reports in the literature on the inhibitory effects of black tea. This study was undertaken to determine the antibacterial effects of black and green teas against the pathogenic Escheriachia coli in vitro.
Materials and Methods: Extracts from both green and black tea (Camellia sinensis) were made using the percolation method. Then different concentrations were prepared from the dried extracts. Viability of E. Coli was assessed by exposing the bacteria to different concentrations of the tea extracts in aqueons media , transferring the culture onto the solid media, and counting the colonies at different times.
This was followed by determining the interactions between black or green tea extracts with some of the antibiotics rountinely used against Gram negative infections using the disc diffusion method (11 times on different days). The data were analysed by the Wilcoxon sign and Kruskal Walis tests.
Results: Both Black an green tea extracts showed either synergistic or antagonistic effects with the antibiotics in a selective dose-dependant manner. The total antioxidant capacity (TAC) of the green tea extract was significantly higher than that of black tea extract (p<0/001).
Conclusion: It is concluded that the antimicrobial effects of tea are likely to be dependent on its TAC. Moreover, it seems that under certain conditions tea polyphenols act as pro-oxidants and exert their cytotoxic effects in this way. Potentially tea or its polyphenol supplements may be used along with antibiotics in infections. |
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| Keywords: Green tea, black tea, Escherichia coli, Synergism, Antimicrobial effect |
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Full-Text [PDF 194 kb]
(3303 Downloads)
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Article type: Research |
Subject:
Food Science
Received: 2008/06/30 | Published: 2007/03/15
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