Antimicrobial activity of essential oils as liquid and vapour applications

Elcocks, Ellena Rae

Abstract

Essential oils produced by plants have been used as antimicrobial agents historically, however, many essential oils remain under-exploited as alternatives to antimicrobials. Therefore, the aim of this thesis was to evaluate the antibacterial efficacy of selected essential oils against bacteria which have the ability to form biofilms. The broad-spectrum potential of several essential oils is demonstrated, with subsequent focus on the strong antimicrobial activity of cinnamon essential oil extracted from Cinnamomum zeylanicum bark. Cinnamon bark essential oil showed broad spectrum activity against a range of bacteria, some of which are relevant clinically, including Pseudomonas aeruginosa which is capable of forming biofilms and implicated in many human diseases. Cinnamon bark essential oil killed planktonic P. aeruginosa at concentrations as low as 0.125% (v/v), and within 2 min when at concentrations of ≥1% (v/v). It also exhibited anti-biofilm activity, in both liquid and vapour form, against P. aeruginosa biofilms grown using a Centre for Disease Control biofilm reactor on polycarbonate and stainless steel surfaces. Liquid application of 2% (v/v) resulted in biofilm eradication in as little as 10 min. When assessed in a novel testing chamber, designed and built as part of this project, cinnamon EO reduced biofilms at vapour concentrations as low as 0.2 μL cm-3. These results provide clear evidence for the potential of cinnamon bark essential to be considered as a novel antimicrobial, and to contribute to the improvement of hygiene and sanitation. As well as addressing the global issue of antibiotic resistance, data presented also provide evidence for the ability of essential oils to inhibit and eradicate biofilms, which increases tolerance of pathogenic bacteria to antimicrobials. Data presented here provide the basis of additional work to investigate development of disinfectant products, evaluate essential oil toxicity, and further study the role of essential oils in combatting antimicrobial resistance.

• Thesis Type: Thesis
• Acceptance Date: Jun 4, 2019
• Publicly Available Date: Feb 6, 2020
• Public URL: https://uwe-repository.worktribe.com/output/1490727
• Award Date: Feb 6, 2020