Leaf Extracts of Selected Gardening Trees Can Attenuate Quorum Sensing and Pathogenicity of PAO1.

An increasing concern on resistance to multiple-antibiotics has led to the discovery of novel agents and the establishment of new precaution strategy. Numerous plant sources have been widely studied to reduce virulence of pathogenic bacteria by interfering cell-to-cell based communication called quorum sensing (QS). Leaf extracts of 17 gardening trees were collected and investigated for their anti-QS effects using a sensor strain CV026. Methanolic extracts of K4 (), K9 () and K13 () leaves were selected for further experiments based on their antagonism effect on QS without inhibiting CV026 growth. Subsequently, the leaf extracts on QS-mediated virulence of PAO1 involved in biofilm formation, motility, bioluminescence, pyocyanin production, QS molecules production, and killing activity were evaluated. The biofilm formation ability and swarming motility of PAO1 were decreased approximately 50% in the presence of these leaf extracts at a concentration of 1 mg/mL. The expression level of of PAO1 and pyocyanin production were also reduced. The three leaf extracts also decreased autoinducer (AI) production in PAO1 without direct degradation, suggesting that AI synthesis might have been suppressed by these extracts. The three leaf extracts also showed anti-infection activity in model. Taken together, these results suggest that methanolic leaf extracts of K4, K9 and K13 have the potential to attenuate the virulence of PAO1.