Anti-Quorum-Sensing Potential of Ethanolic Extracts of Aromatic Plants from the Flora of Cyprus

Abstract

Quorum sensing (QS) is a form of intra- and inter-species communication system employed by bacteria to regulate their collective behavior in a cell population-dependent manner. QS has been implicated in the virulence of several pathogenic bacteria. This work aimed to investigate the anti-QS potential of ethanolic extracts of eight aromatic plants of Cyprus, namely, Origanum vulgare subsp. hirtum, Rosmarinus officinalis, Salvia officinalis, Lavendula spp., Calendula officinalis, Melissa officinalis, Sideritis cypria, and Aloysia citriodora. We initially assessed the effects of the extracts on autoinducer 2 (AI-2) signaling activity, using Vibrio harveyi BB170 as a reported strain. We subsequently assessed the effect of the ethanolic extracts on QS-related processes, including biofilm formation and the swarming and swimming motilities of Escherichia coli MG1655. Of the tested ethanolic extracts, those of Origanum vulgare subsp. hirtum, Rosmarinus officinalis, and Salvia officinalis were the most potent AI-2 signaling inhibitors, while the extracts from the other plants exhibited low to moderate inhibitory activity. These three ethanolic extracts also inhibited the biofilm formation (>60%) of E. coli MG1655, as well as its swimming and swarming motilities, in a concentration-dependent manner. These extracts may be considered true anti-QS inhibitors because they disrupt QS-related activities of E. coli MG1655 without affecting bacterial growth. The results suggest that plants from the unexplored flora of Cyprus could serve as a source for identifying novel anti-QS inhibitors to treat infectious diseases caused by pathogens that are resistant to antibiotics.

Evaluation of the Antibacterial and Antibiofilm Effects of Ethyl Acetate Root Extracts from Vernonia adoensis (Asteraceae) against Pseudomonas aeruginosa

“…In this study, we investigated the effects of V. adoensis root extract on P. aeruginosa swimming and swarming motilities and found that the extract had no effect on the motility of the bacterium. However, there are studies which have shown that plant extracts can inhibit the motility of P. aeruginosa [ 65 ]. Antibiofilm agents may influence biofilm formation by damaging microbial membrane structures, inhibiting peptidoglycan synthesis and/or modulating quorum sensing [ 66 ].…”

Effects of chlorogenic acid on antimicrobial, antivirulence, and anti-quorum sensing of carbapenem-resistant Klebsiella pneumoniae

“…The steps for detecting the activity of culture supernatant can refer to reference and be modified as appropriate ( Panayi et al, 2022 ). The steps are as follows: Vibrio harveyi ( V. harveyi ) BB170 is inoculated in autoinducer bioassay (AB) culture medium and cultured overnight at 30°C.…”

“…The steps for detecting the activity of culture supernatant can refer to reference and be modified as appropriate (Panayi et al, 2022). The steps are as follows: Vibrio harveyi (V. harveyi) BB170 is inoculated in autoinducer bioassay (AB) culture medium and cultured overnight at 30 • C. Before detection, the overnight culture solution of V. harveyi BB170 was diluted with fresh AB medium at a ratio of 1:5,000, and shaken well.…”

Virulence factors and quorum sensing as targets of new therapeutic options by plant-derived compounds against bacterial infections caused by human and animal pathogens

“…As shown in Table-2 [49,[52][53][54][55][56][57][58], a Delftia tsuruhatensis extract inhibited biofilm, motility, elastase activity, and protease activity in P. aeruginosa. The extract suppressed the expression of the quorum sensing genes LasI, LasR, RhlI, and RhlR.…”

“…Similarly, copper nanoparticles synthesized using Cardiospermum halicacabum leaf extract inhibited the development of P. aeruginosa biofilms [61]. The nanoparticles could attach to the bacterial cells, disrupting the bacterial cell wall or cell membrane to inhibit biofilm formation [58,61].…”