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Aggregation of Staphylococcus aureus following treatment with the antibacterial flavonol galangin.

Cushnie, T.P.T.; Hamilton, V.E.S.; Chapman, D.G.; Taylor, P.W.; Lamb, A. J.


T.P.T. Cushnie

V.E.S. Hamilton

D.G. Chapman

P.W. Taylor


Aim: The flavonol galangin, an antimicrobial constituent of the traditional medicines propolis and Helichrysum aureonitens, is being assessed as part of an ongoing investigation into the antibacterial activity of flavonoids. The present study sought to establish whether galangin has any aggregatory effect on bacterial cells. Methods and Results: In preparatory time-kill assays, 50 μg ml-1 of galangin was found to reduce colony counts of c. 5 × 107 CFU ml-1Staphylococcus aureus NCTC 6571 by approximately 15 000-fold during 60 min of incubation. Subsequent light microscopy studies demonstrated significant increases in the number of large clusters of bacterial cells in populations treated with the flavonol. Conclusion: Data presented here show that galangin causes aggregation of bacterial cells. Significance and Impact of the Study: The finding that galangin causes bacterial cells to clump together may implicate the cytoplasmic membrane as a target site for this compound's activity. More importantly, this observation indicates that decreases in CFU numbers detected in time-kill and minimum bactericidal concentration (MBC) assays in previous investigations were at least partially attributable to this aggregatory effect. This raises the possibility that galangin is not genuinely bactericidal in action, and calls into question the suitability of time-kill and MBC assays for determining the nature of activity of naturally occurring flavonoids.


CUSHNIE, T.P.T., HAMILTON, V.E.S., CHAPMAN, D.G., TAYLOR, P.W. and LAMB, A.J. 2007. Aggregation of Staphylococcus aureus following treatment with the antibacterial flavonol galangin. Journal of applied microbiology [online], 103(5), pages 1562-1567. Available from:

Journal Article Type Article
Acceptance Date Feb 26, 2007
Online Publication Date Jun 13, 2007
Publication Date Nov 30, 2007
Deposit Date Aug 30, 2017
Publicly Available Date Aug 30, 2017
Journal Journal of applied microbiology
Print ISSN 1364-5072
Electronic ISSN 1365-2672
Publisher Wiley Open Access
Peer Reviewed Peer Reviewed
Volume 103
Issue 5
Pages 1562-1567
Keywords Galangin; Antibacterial; Flavonoid; Aggregation; Timekill; MBC; Bactericidal; Bacteriostatic
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