Anti-Quorum Sensing Activity of 12 Essential Oils on and Specific Action of -Menthenolide from Corsican ssp. .

Quorum sensing (QS) is a bacterial communication mechanism used to express various survival or virulence traits leading to enhanced resistance. is a commonly used strain that highlights anti-QS action of bioactive substances. Here, we wanted to see if 12 selected essential oils (EO) could exert anti-QS activity. We measured the sublethal minimal QS inhibitory concentration (MQSIC) by assessing violacein production of along with bacterial growth. To confirm the QS disruption, we also proceed to surface bacterial observations using scanning electron microscopy (SEM). We showed that menthenolide extracted and isolated from a plant endemic to occidental Mediterranean Sea islands, ssp. , acts as an inhibitor of violacein production and biofilm formation. Measured MQSIC was much lower than the minimal inhibitory concentration (MIC): 0.10 mg·mL vs. 3.00 mg·mL. Moreover, disturbance of QS-related traits was confirmed by the degradation of biofilm matrix. There is a clear structure⁻activity relationship between menthenolide and anti-QS activity. Indeed, its isomer molecule (mintlactone) exerts a poor anti-QS action. These results indicate that inhibition of violacein production and biofilm formation by menthenolide might be related to a disruption in the QS mechanism.