Mixtures of Essential Oils in an Air Conditioning Prototype to Reduce the Prevalence of Airborne Pathogenic Bacteria

Abstract

The rationale for this work was to test the possibility of creating a protective atmosphere by using natural compounds to minimize hazards from chemicals and to control the risk of common infections. The antimicrobial activities of essential oils of Agronis fragrans, Cinnamomum zeylanicum, Lavandula angustifolia, Melaleuca alternifolia (tea tree), Melaleuca nesophila (honey myrtle), Pelargonium x asperum (geranium), Pogostemon cablin (patchouli), Thymus serpyllum, and Thymus vulgaris were evaluated against an array of environmental-borne pathogenic bacteria. Gram-positive bacteria included Bacillus subtilis and Staphylococcus aureus; four Gram-negative bacteria covered Acinetobacter baumanii, Escherichia coli, Klebsiella pneumoniae, and Pseudomonas aeruginosa. In addition, eleven isolates of methicillin-resistant S. aureus (MRSA) and a multidrug-resistant A. baumanii were incorporated. In agar disc diffusion tests, cinnamon had shown the strongest activity that could inhibit all pathogens, followed by lemon thyme, honey myrtle and lavender, while pachouli exhibited the weakest inhibition. Though fragonia possessed a broad range of activity against all pathogens, it did not inhibit some of the MRSA isolates. Cinnamon and lemon thyme demonstrated strong activity measured by minimal inhibitory concentrations (MICs) and minimal bactericidal concentrations. In disk volatilization assay, thyme oil demonstrated the greatest inhibition, followed by lemon thyme, while no inhibition from patchouli was observed. Subsequently, the composition of the atmosphere generated by three different oil blends in our invented portable air-conditioning prototype was assessed. The results showed that mixture of oil blend No. 2 can produce good synergistic effect in reducing the prevalence of airborne pathogens, and thus preventing the spreading of infections.

The Antimicrobial and Antibiofilm In Vitro Activity of Liquid and Vapour Phases of Selected Essential Oils against Staphylococcus aureus

“…These results cannot be directly compared with results from other studies due to diversity of Inverted Petri Dish assay protocols applied. Nevertheless, the anti-staphylococcal efficacy of vapour phases of thyme oil has been proven in numerous studies [ 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 ]. On the other hand, some studies have also indicated significant activity of TT-EO, E-EO, B-EO, L-EO vapour against S. aureus [ 40 , 42 , 47 , 48 , 49 ], whereas other studies are consistent with our results [ 40 , 41 ].…”

“…Nevertheless, the anti-staphylococcal efficacy of vapour phases of thyme oil has been proven in numerous studies [40][41][42][43][44][45][46][47]. On the other hand, some studies have also indicated significant activity of TT-EO, E-EO, B-EO, L-EO vapour against S. aureus [40,42,[47][48][49], whereas other studies are consistent with our results [40,41]. Differences in applied methodologies such as volume and concentration of oil used, addition of oil solvents, testing several samples on the same plate, paper disc diameter, or agar surface height, are suggested to explain the discrepancies in outcomes.…”

The antibacterial effectiveness of lavender essential oil against methicillin-resistant Staphylococcus aureus: a systematic review

“…Many were conducted in Poland ( Budzynska et al, 2011 ; Kot et al, 2019 ; Kwiatkowski et al, 2019 ; Adaszynska-Skwirzynska et al, 2020 ; Brozyna et al, 2021 ). Others were conducted in United States, Jordan, Algeria, Italy, China, UK, Spain, Turkey, Romania, Bosnia and Herzegovina, Belgium, Portugal, Australia and Morocco ( Edwards-Jones et al, 2004 ; Kirmizibekmez et al, 2009 ; Roller et al, 2009 ; Warnke et al, 2009 ; Voravuthikunchai et al, 2012 ; Haba et al, 2014 ; Said et al, 2015 ; Bekka-Hadji et al, 2016 ; Predoi et al, 2018 ; Bona et al, 2019 ; Koca et al, 2019 ; Man et al, 2019 ; Oancea et al, 2019 ; Ribeiro et al, 2020 ; Abers et al, 2021 ; Cui et al, 2021 ; Di Vito et al, 2021 ; Mesic et al, 2021 ).…”

“…( Edwards-Jones et al, 2004 ; Roller et al, 2009 ; Warnke et al, 2009 ; Voravuthikunchai et al, 2012 ; Said et al, 2015 ; Bekka-Hadji et al, 2016 ; Bona et al, 2019 ; Oancea et al, 2019 ; Brozyna et al, 2021 ; Mesic et al, 2021 ). Five studies were interested in the antimicrobial activity of LEO vapours ( Edwards-Jones et al, 2004 ; Roller et al, 2009 ; Voravuthikunchai et al, 2012 ; Abers et al, 2021 ; Brozyna et al, 2021 ). Two studies also concerned themselves with LEO activity against S. aureus biofilms ( Budzynska et al, 2011 ; Brozyna et al, 2021 ).…”

“…Studies which tested the antibacterial effect of lavender oil vapours used modified versions of agar diffusion and independently designed methods, such as the air conditioner model (( Edwards-Jones et al, 2004 ; Voravuthikunchai et al, 2012 ; Abers et al, 2021 ; Brozyna et al, 2021 ).…”