Inhibition of Quorum Sensing (QS) in Yersinia enterocolitica by an Orange Extract Rich in Glycosylated Flavanones

Flavanones, flavonoids abundant in Citrus, have been shown to interfere with quorum sensing (QS) and affect related physiological processes. We have investigated the QS-inhibitory effects of an orange extract enriched in O-glycosylated flavanones (mainly naringin, neohesperidin, and hesperidin). The QS-inhibitory capacity of this extract and its main flavanone components was first screened using the bacteriological monitoring system Chromobacterium violaceum. We next examined the ability of the orange extract and of some of the flavanones to (i) reduce the levels of the QS mediators produced by Y. enterocolitica using HPLC-MS/MS, (ii) inhibit biofilm formation, and (iii) inhibit swimming and swarming motility. Additionally, we evaluated changes in the expression of specific genes involved in the synthesis of the lactones (yenI, yenR) and in the flagellar regulon (flhDC, fleB, fliA) by RT-PCR. The results showed that the orange extract and its main flavanone components inhibited QS in C. violaceum, diminished the levels of lactones secreted by Y. enterocolitica to the media, and decreased QS-associated biofilm maturation without affecting bacterial growth. Among the tested compounds, naringin was found to inhibit swimming motility. Exposure to the orange extract and (or) to naringin was also found to be associated with induction of the transcription levels of yenR, flhDC, and fliA. This work shows the in vitro QS-inhibitory effects of an orange extract enriched in flavanones against a human enteropathogen at doses that can be achieved through the diet and suggests that consumption of these natural extracts may have a beneficial antipathogenic effect.