The fruit of Q. brantii are used in decoction or as powder to treat acute diarrhea and inflammation in traditional medicin. Background: In recent years, a number of antibiotics have lost their effectiveness due to the development of resistant strains, mostly through the expression of resistance genes. Objectives: The aim of the present study was to investigate the antimicrobial property of Quercus brantii fruits and compare its effects with some current antibiotics. Materials and Methods: The antimicrobial activities of an ethanol extract of Q. brantii (Oak) fruits (brown cortex: B.C and white core: W.C) were tested in vitro against eight reference strains of enteric pathogenic bacteria. The antimicrobial activities of the extracts were examined based on the disc diffusion method. The results were evaluated as inhibition zones around the discs impregnated with B.C and W.C extracts at different concentrations (2 to 10 %). Results: The antibacterial effect of the B.C ethanolic extract on Escherichia coli was significant and had a concentration-related effect, although there was no significant effect found on Helicobacter pylori. The W.C ethanolic extract has a high antimicrobial effect on Streptococcus pyogenes; at the same time significant antibacterial activity occurred against H pylori. Comparisons between the antimicrobial activities of these extracts (B.C and W.C) and standard antibiotics; gentamicin, colistin, and methicillin, showed that in the most commonly tested bacteria the antibacterial activity of these extracts was even greater than with the antibiotics. Analysis of the extracts components by gas chromatography, showed that tannins and phenolic compounds could be responsible for these antimicrobial activities. Conclusions: The results of this study showed that different parts of Q. brantii have antimicrobial activity against gastrointestinal bacterial pathogens. These antimicrobial activities, in almost all cases, were greater than with standard antibiotics.

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