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J Glob Antimicrob Resist · Sep 2017
Inhibition of Pseudomonas aeruginosa quorum sensing by subinhibitory concentrations of curcumin with gentamicin and azithromycin.
- Shahin Bahari, Habib Zeighami, Hesam Mirshahabi, Shekoufeh Roudashti, and Fakhri Haghi.
- Department of Microbiology and Virology, Zanjan University of Medical Sciences, Zanjan, Iran.
- J Glob Antimicrob Resist. 2017 Sep 1; 10: 21-28.
ObjectivesPseudomonas aeruginosa quorum sensing (QS) circuits regulate virulence factors and co-ordinate bacterial pathogenicity. This study aimed to investigate the inhibitory activity of subinhibitory concentrations of curcumin with azithromycin and gentamicin against P. aeruginosa QS-related genes and virulence factors.MethodsThe minimum inhibitory concentrations (MICs) and synergistic activity of curcumin with azithromycin and gentamicin against P. aeruginosa PAO1 were determined using broth microdilution and checkerboard titration methods, respectively. The activity of sub-MICs (1/4× and 1/16× MIC) of curcumin on the QS signal molecules was assessed using a reporter strain assay. The influence of sub-MICs of curcumin, azithromycin and gentamicin alone and in combination on motility and biofilm formation was also determined and was confirmed by RT-PCR to test the expression of the QS regulatory genes lasI, lasR, rhlI and rhlR.ResultsAddition of curcumin drastically decreased the MIC of azithromycin and gentamicin. Curcumin showed synergistic effects with azithromycin and gentamicin. Treated PAO1 cultures in the presence of curcumin showed a significant reduction of signals C12-HSL and C4-HSL (P<0.05). Sub-MICs (1/4× and 1/16× MIC) of curcumin, azithromycin and gentamicin alone and in combination significantly reduced swarming and twitching motilities as well as biofilm formation. Expression of QS regulatory genes lasI, lasR, rhlI and rhlR using 1/4× MIC of curcumin, azithromycin and gentamicin alone and in combination was decreased significantly compared with untreated PAO1.ConclusionsThese results indicate that a combination of sub-MIC of curcumin with azithromycin and gentamicin exhibited synergism against P. aeruginosa QS systems.Copyright © 2017 International Society for Chemotherapy of Infection and Cancer. Published by Elsevier Ltd. All rights reserved.
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