Eugenol exhibits anti-virulence properties by competitively binding to quorum sensing receptors

Abstract

The primary objective of this study was to ascertain the anti-biofilm and anti-virulence properties of sub-minimum inhibitory concentration (MIC) levels of eugenol against the standard strain PAO1 and two multi-drug resistant P. aeruginosa clinical isolates utilizing quorum sensing inhibition (QSI). Eugenol at 400 μM significantly reduced biofilm formation on urinary catheters and the virulence factors (VF) including extracellular polysaccharides, rhamnolipid, elastase, protease, pyocyanin, and pyoverdine (p < 0.001). Further, eugenol exhibited a marked effect on the production of QS signals (AIs) (p < 0.001) without affecting their chemical integrity. In silico docking studies demonstrated a stable molecular binding between eugenol and QS receptor(s) in comparison with respective AIs. Investigation on reporter strains confirmed the competitive binding of eugenol to a QS receptor (LasR) as the possible QSI mechanism leading to significant repression of QS associated genes besides the VF genes (p < 0.001). This study provides insights, for the first time, into the mechanism of the anti-virulence properties of eugenol.

Keywords:

• Catheter associated urinary tract infections
• Pseudomonas aeruginosa
• quorum sensing
• virulence factors
• eugenol
• biofilm

Acknowledgements

The authors acknowledge the GC-MS facility and SEM facility (funded by the Department of Science and Technology-FIST program, Government of India) at VIT University, for providing the necessary services to conduct this study. The authors are thankful to Ms Leema George and Mr Jobin John Jacob, School of Biosciences and Technology, VIT University for the fluorescent staining and microscope examinations, respectively. The authors thank the computational and bioinformatics facility in Maharani Lakshmi Ammanni College for Women, Bioinformatics Facility (Funded by the Department of Biotechnology (DBT), Government of India). The authors acknowledge the language usage and editing facility of the School of Social Science and Languages, VIT University, Vellore. The authors express their gratitude for the suggestions made by Dr Ravishankar Babu and Dr Prasanth Kumar NS on scientific writing, English grammar and usage, to improve the quality of the manuscript. The authors acknowledge Dr Jack G. Kleinman, Professor of Nephrology, Medical College of Wisconsin, Milwaukee, USA for proof reading the manuscript.