Green tea extract has moderate and wide-spectrum inhibitory effects on the growth of many types of pathogenic bacteria, according to in vitro tests, including seven strains of Staphylococcus spp., seven strains of Streptococcus spp., one strain of Corynebacterlum suls, 19 strains of Escherichia coll and 26 strains of Salmonella spp. (Ishihara et al 2001). Green tea has also been found to inhibit Helicobacter pylori in an animal model (Matsubara et al 2003). According to one study, which compared the antibacterial activity of black, green and oolong tea, it seems that fermentation adversely affects antibacterial activity, as green tea exhibited the strongest effects, and black tea the weakest (Chou et al 1999). An in vitro study has demonstrated that © 2007 Elsevier Australia
green tea can significantly lower bacterial endotoxin-induced cytokine release and therefore may reduce mortality from sepsis (Chen et al 2005). Oral pathogens Both in vitro and in vivo tests have identified strong antibacterial activity against a range of oral pathogens, such as Streptococcus mutans, S. salivarius and E. coli (Otake et al 1991, Rasheed & Haider 1998). The mechanism of action appears to involve anti-adhesion effects, with the strongest activity associated with epigallocatechin gallate and epicatechin gallate. Green tea catechins have also showed an antibacterial effect against Porphyromonas gingivalis and Prevotella spp. in vitro (Hirasawa et al 2002). Furthermore, green tea polyphenols, especially epigallocatechin gallate, have been found to completely inhibit the growth and adherence of P. gingivalis on buccal epithelial cells (Sakanaka et al 1996).
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