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Antimicrobial Effects of Blueberry, Raspberry, and Strawberry Aqueous Extracts and their Effects on Virulence Gene Expression in Vibrio cholerae
Author(s) -
Khalifa Hazim O.,
Kamimoto Maki,
Shimamoto Toshi,
Shimamoto Tadashi
Publication year - 2015
Publication title -
phytotherapy research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.019
H-Index - 129
eISSN - 1099-1573
pISSN - 0951-418X
DOI - 10.1002/ptr.5436
Subject(s) - vibrio cholerae , blowing a raspberry , antimicrobial , berry , microbiology and biotechnology , virulence , biology , listeria monocytogenes , bacteria , pathogenic bacteria , gene expression , food science , gene , botany , biochemistry , genetics
The antimicrobial effects of aqueous extracts of blueberry, raspberry, and strawberry on 13 pathogenic bacteria were evaluated. The minimum inhibitory concentrations and minimum bactericidal concentrations of the extracts were determined before and after neutralization to pH 7.03 ± 0.15. Both Gram‐positive and Gram‐negative pathogenic bacteria were selectively inhibited by the non‐neutralized berries. Blueberry was the best inhibitor, and Vibrio and Listeria were the most sensitive bacteria. After neutralization, blueberry affected only Vibrio and Listeria , whereas the antimicrobial activities of raspberry and strawberry were abolished. The total contents of phenolics, flavonoids, and proanthocyanidins in the extracts were measured with colorimetric methods and were highest in strawberry, followed by raspberry, and then blueberry. We also studied the effects of sub‐bactericidal concentrations of the three berry extracts on virulence gene expression in Vibrio cholerae . Real‐time quantitative reverse transcription–polymerase chain reaction revealed that the three berry extracts effectively repressed the transcription of the tcpA gene. Raspberry also repressed the transcription of the ctxA gene, whereas blueberry and strawberry did not. However, the three berry extracts did not affect the transcription of toxT . These results suggest that the three berry extracts exert potent antimicrobial effects and inhibit the expression of the virulence factors of V. cholerae . Copyright © 2015 John Wiley & Sons, Ltd.