Effects of Essential Oils from Cymbopogon spp. and Cinnamomum verum on Biofilm and Virulence Properties of Escherichia coli O157:H7

Abstract

Every year, the pharmaceutical and food industries produce over 1000 tons of essential oils (EOs) exploitable in different fields as the development of eco-friendly and safe antimicrobial inhibitors. In this work we investigated the potential of some EOs, namely Cinnamomum verum, Cymbopogon martini, Cymbopogoncitratus and Cymbopogon flexuosus, on the growth, biofilm formation and gene expression in four strains of enterohemorrhagic Escherichia coli O157:H7. All EOs were analyzed by gas chromatography-mass spectrometry (GC-MS). The antimicrobial activity was performed by using dilutions of EOs ranging from 0.001 to 1.2% (v/v). Subinhibitory doses were used for biofilm inhibition assay. The expression profiles were obtained by RT-PCR. E. coli O157:H7 virulence was evaluated in vivo in the nematode Caenorhabditis elegans. All EOs showed minimal inhibitory concentrations (MICs) ranging from 0.0075 to 0.3% (v/v). Cinnamomum verum bark EO had the best activity (MIC of 0.0075% (v/v) in all strains) while the C. verum leaf EO had an intermediate efficacy with MIC of 0.175% (v/v) in almost all strains. The Cymbopogon spp. showed the more variable MICs (ranging from 0.075 to 0.3% (v/v)) depending on the strain used. Transcriptional analysis showed that C. martini EO repressed several genes involved in biofilm formation, virulence, zinc homeostasis and encoding some membrane proteins. All EOs affected zinc homeostasis, reducing ykgM and zinT expression, and reduced the ability of E. coli O157:H7 to infect the nematode C. elegans. In conclusion, we demonstrated that these EOs, affecting E. coli O157:H7 infectivity, have a great potential to be used against infections caused by microorganisms.

Cinnamomum: The New Therapeutic Agents for Inhibition of Bacterial and Fungal Biofilm-Associated Infection

“…In this regard, E. coli frequently leads to biofilm-associated opportunistic infections like endometritis, diarrhea, and mastitis ( Kim et al., 2017 ; Wang et al., 2020 ). Antibiotics can help alleviate disease symptoms and duration, but several E. coli species have developed resistance to antibiotics due to antibiotic overuse over the last 50 years ( Scotti et al., 2021 ). Hence, Cinnamomum was used to inhibit the attachment and formation of biofilms by E. coli to manage infection caused by this bacterium.…”

“…To this end, the results of recent experimentation showed that C. verum essential oil (CVEO) inhibited the biofilm formation of EHEC clinical isolates. In addition, the microscopic examination revealed the following characteristics of biofilm cells in the presence of CVEO: sparse microcolonies and individual cells with fewer and shorter interconnecting meshes between cells, but no discernible morphological changes ( Scotti et al., 2021 ).…”

Use of nature‐derived antimicrobial substances as safe disinfectants and preservatives in food processing industries: A review

“…et al, 2021). C. martini essential oil is also responsible for inhibiting several genes involved in the formation of E. coli O157:H7 biofilm (Scotti et al, 2021). Cinnamaldehyde was observed to prevent biofilm formation by Campylobacter spp.…”

“…Thymol is also responsible for inhibiting P. aeruginosa biofilm by limiting the bacterial swimming and swarming motility (Liu et al, 2021). C. martini essential oil is also responsible for inhibiting several genes involved in the formation of E. coli O157:H7 biofilm (Scotti et al., 2021). Cinnamaldehyde was observed to prevent biofilm formation by Campylobacter spp.…”

“…Scotti et al. (2021) investigated the antimicrobial activity of Cinnamomum verum , Cymbopogon martini , Cymbopogon citratus , and Cymbopogon flexuosus on E . coli O157:H7.…”