Gentamicin Augments the Quorum Quenching Potential of Cinnamaldehyde In Vitro and Protects Caenorhabditis elegans From Pseudomonas aeruginosa Infection

Abstract

The quorum sensing (QS) circuitry of Pseudomonas aeruginosa represents an attractive target to attenuate bacterial virulence and antibiotic resistance. In this context, phytochemicals harboring anti-virulent properties have emerged as an alternative medicine to combat pseudomonal infections. Hence, this study was undertaken to investigate the synergistic effects and quorum quenching (QQ) potential of cinnamaldehyde (CiNN) in combination with gentamicin (GeN) against P. aeruginosa. The QQ activity of this novel combination was evaluated using a QS reporter strain and synergism was studied using chequerboard assays. Further, the genotypic and phenotypic expression of pseudomonal virulence factors was examined alongside biofilm formation. The combination of CiNN and GeN exhibited synergy and promising anti-QS activity. This drug combination was shown to suppress AHL production and downregulate the expression of critical QS genes in P. aeruginosa PAO1. Molecular docking revealed strong interactions between the QS receptors and CiNN, asserting its QQ potential. Bacterial motility was compromised along with a significant reduction in pyocyanin (72.3%), alginate (58.7%), rhamnolipid (33.6%), hemolysin (82.6%), protease (70.9%), and elastase (63.9%) production. The drug combination successfully eradicated preformed biofilms and inhibited biofilm formation by abrogating EPS production. Our findings suggest that although GeN alone could not attenuate QS, but was able to augment the anti-QS potential of CiNN. To validate our results using an infection model, we quantified the survival rates of Caenorhabditis elegans following PAO1 challenge. The combination significantly rescued C. elegans from PAO1 infection and improved its survival rate by 54% at 96 h. In summary, this study is the first to elucidate the mechanism behind the QQ prospects of CiNN (augmented in presence of GeN) by abrogating AHL production and increasing the survival rate of C. elegans, thereby highlighting its anti-virulent properties.

Design of Cinnamaldehyde- and Gentamicin-Loaded Double-Layer Corneal Nanofiber Patches with Antibiofilm and Antimicrobial Effects

“…aeruginosa and S. aureus, which supports the presented findings. , Biofilm formation in P. aeruginosa has been regarded as a crucial virulence feature that contributes to resistance against antimicrobial agents.…”

Inhibitory effect of natural compounds on quorum sensing system in Pseudomonas aeruginosa: a helpful promise for managing biofilm community

“…The molecular docking analysis demonstrated robust binding interactions between the QS receptors and cinnamaldehyde, confirming its significant potential as a QS modulator. This dual treatment effectively eliminated pre-existing biofilms and suppressed the creation of new biofilms by disrupting the production of EPS ( Chadha et al, 2022 ). Noteworthy, the authors suggested that the synergistic interaction between the drugs can be related to their unique mechanisms of action.…”

“…This renders the bacterial cell more vulnerable as the medications can simultaneously target two separate cellular areas. In addition, cinnamaldehyde efficiently inhibits the QS circuits in P. aeruginosa by reducing the expression of QS genes and preventing the production of AHL molecules ( Shaw and Wuest, 2020 ; Chadha et al, 2022 ). The mentioned function of cinnamaldehyde was attributed to its potent interaction with the QS receptors of P. aeruginosa .…”

“…As a result, this reduces the activity of the virulence factors and the creation of biofilms associated with the QS system, consequently decreases the pathogenesis of the bacterium. Furthermore, the addition of gentamycin increases the effectiveness of inhibiting QS and enhances the ability of cinnamaldehyde to reduce virulence ( Chadha et al, 2022 ).…”

Recent advances in therapeutic targets identification and development of treatment strategies towards Pseudomonas aeruginosa infections

“…It also reduces the relative expression of four QS genes (lasI, lasR, rhlI, rhlR) and the biofilm-related gene ndvB [79]. On its side, the combination of cinnamaldehyde with gentamicin represses acylhomoserine lactones production and downregulates the expression of critical QS genes, to substantially diminish pyocyanin, alginate, rhamnolipid, hemolysin, protease, and elastase production, to successfully suppress preformed biofilms and to impair biofilm formation by disrupting EPS production [80].…”