Citrus paradisi and Citrus reticulata essential oils interfere with Pseudomonas aeruginosa quorum sensing in vivo on Caenorhabditis elegans

D'ALMEIDA ROMINA ELISA; SUED NAHIR; ARENA MARIO E

Conferencia; 23rd International C. elegans Conference; 2021

Genetic Society of America (GSA)

To overcome the problem of widespread antibiotic resistance, increasing attention has been paid to natural products with anti-quorum sensing (QS) properties as potential therapeutic agents. C. paradisi and C. reticulata Essential Oils (EOs) have shown the ability to interfere in vitro with Pseudomonas aeruginosa QS signaling (mainly on acyl-homoserine lactones (AHLs) production and elastase activity) and biofilm formation leading to an attenuation of the microbial virulence. C. paradisi (grapefruit) and C. reticulata (mandarin) were cultivated in Argentina, and their EOs (commercial samples) were obtained by cold-pressing and cold-pressing followed by steam distillation. These citrus EOs are complex mixtures of mainly monoterpene (94-98%) and sesquiterpene hydrocarbons, as well as their oxygenated derivatives, with limonene as their main component (88-89.8%). In our study, Citrus paradisi and C. reticulata EOs were screened to assess their ability to extend the survival of infected Caenorhabditis elegans with Pseudomonas aeruginosa PA14 and PAO1, as well as their effect on bacterial growth and biofilm formation. We used different assays, as these strains can kill C. elegans by a variety of mechanisms: fast killing mediated by phenazines, slow killing mediated by QS, and paralytic assay mediated by HCN. Also, we used a food choice assay to study the effect of EOs on AHLs by PA14 in vivo. The toxicity of mandarin and grapefruit EOs was evaluated on survival, brood size, and body length of C. elegans. Our results showed that mandarin and grapefruit EOs at 0.2 mg/mL were safe for the nematodes, significantly inhibited biofilm formation (up to 50%), and improved worm survival following infection in the three assays evaluated (40-74%) without affecting PA14 and PAO1 growth. When the nematodes were given to choose between PA14 grown alone or in presence of the citrus EOs, there was a significant difference in the election of food for those with EOs. C. paradisi EOs were more effective in reducing the virulence of P. aeruginosa in comparison with C. reticulata EOs and limonene, their main component. In addition, we observed no difference between the in vivo activity of EOs of each citrus species obtained by the two methodologies described. In conclusion, targeting the QS system is gaining much attention as an infection control strategy, therefore C. paradisi and C. reticulata EOs could be proposed as sources of anti-QS agents for controlling human P. aeruginosa infections.