Attenuation of Listeria monocytogenes Virulence by Cannabis sativa L. Essential Oil

Abstract

Anti-virulence strategies are being explored as a novel approach to combat pathogens. Such strategies include inhibition of surface adhesion, tissue invasion, toxin production, and/or interference with the gene regulation of other virulence traits. Listeria monocytogenes, the causative agent of listeriosis, is a facultative intracellular food pathogen characterized by a wide distribution in the environment. Its ability to persist within biofilms and to develop resistance to sanitizers is the cause of significant problems in food processing plants and of steep costs for the food industry. In humans, the treatment of listeriosis is hampered by the intracellular location of listeriae and the poor intracellular penetration of some antibiotics. Eleven L. monocytogenes isolates from patients who were diagnosed with invasive listeriosis in Italy in 2014–2016 were studied. This in vitro and in vivo study explored the antibacterial and anti-virulence properties of a steam-distilled essential oil of Cannabis sativa L., which is being intensively investigated for its high content in powerful bioactive phytochemicals. Susceptibility experiments demonstrated a moderate bactericidal activity of the essential oil (Minimum Bactericidal Concentration > 2048 μg/mL). Assessment of the effects of sublethal concentrations of the essential oil on L. monocytogenes virulence traits demonstrated a significant action on motility. Listeriae were non-motile after exposure to the essential oil. Light and scanning electron microscopy documented aggregates of listeriae with the flagella trapped inside the cluster. Real-time RT-PCR experiments showed downregulation of flagellar motility genes and of the regulatory gene prfA. The ability to form biofilm and to invade Caco-2 cells was also significantly reduced. Galleria mellonella larvae infected with L. monocytogenes grown in presence of sublethal concentrations of the essential oil showed much higher survival rates compared with controls, suggesting that the extract inhibited tissue invasion. Food contamination with L. monocytogenes is a major concern for the food industry, particularly for plants making ready-to-eat and processed food. The present work provides a baseline in the study of the anti-virulence properties of the C. sativa essential oil against L. monocytogenes. Further studies are needed to understand if it could be used as an alternative agent for the control of L. monocytogenes in food processing plants.

Galleria mellonella as a consolidated in vivo model hosts: New developments in antibacterial strategies and novel drug testing

“…The ability of a sublethal concentration (256 μg/mL) of Cannabis sativa L. essential oil extracted from the French monoecious variety Futura 75 to attenuate the virulence of eleven L. monocytogenes strains isolated from patients diagnosed with invasive listeriosis has been evaluated by a survival experiment. After 6 days of infection survival rates of infected groups compared with those who were not infected increased remarkably (from 50 to 90%) [72].…”

In SilicoIdentification of Novel PrfA Inhibitors to Fight Listeriosis: A Virtual Screening and Molecular Dynamics Studies

“…It has recently been described that Granzyme B seriously impairs L. monocytogenes infection by degrading Listeriolysin O (LLO) which is one of the majors virulent factors activated by PrfA [43]. A recently published report also supports this thesis where steam-distilled essential oil of Cannabis sativa was shown to down-regulate PrfA [45]. In the mentioned work the ability of L monocytogenes to invade Caco-2 cells was significantly reduced in the presence of the essential oil and infected Galleria mellanella larvae in the presence of the essential oil presented higher survival rates than the corresponding control experiments [45].…”

Chemical characterization and antimicrobial activity of Campomanesia aurea against three strains of Listeria monocytogenes

“…Some studies indicated that the essential oils have antimicrobial activity against many pathogens, regarding bacteria, as well as fungi (Ferronatto et al, 2007;Santurio et al, 2011). Marini et al (2018), tested the antimicrobial activity of the essential oil of Cannabis sativa against Listeria monocytogenes, and obtained the MBC ≥ 2.048 mg/mL, thus suggested bactericidal activity due to the presence of the identified main compounds of the oil, myrcene and α-pinene. These two substances could also be identified in the present study, specifically the α-pinene in both oils (EOA and EOO) and the myrcene only in the EOO.…”

“…L. monocytogenes is known to cause the disease listeriosis, which affects principally immunocompromised patients, thereby having a mortality rate of 30%. Furthermore, the bacteria bear the ability for biofilm formation, and by this way developing resistance to sanitizers and antimicrobial agents, thus provoking serious problems to food industries (Oliveira et al, 2016b;Rogalla and Bomar, 2018;Marini et al, 2018).…”