Purpose:
The purpose of the study was to assess the antibacterial effectiveness of vapours of essential oils against aerosolised cells of Salmonella enterica and Listeria seeligeri that can contaminate food.
Methods:
Antimicrobial gels containing essential oils, both with and without zinc, were allowed to vaporise inside a glass chamber for 10 minutes. A collision nebulizer was used to generate bacterial aerosols. These aerosols were then passed through the vapours of the essential oils and collected using a six-stage Andersen sampler. The Andersen sampler enabled the capture of aerosols from 7 to 0.65 µm in size. The aerosols from different stages of the impact sampler were cultured using standard techniques. These results were compared to the number of culturable microbes found in control microbial aerosols without exposure to the evaporated essential oils. Additionally, the antimicrobial activity of essential oils released from solutions was also tested.
Results:
Following a 10-minute evaporation period, the essential oils released from the antimicrobial gel containing zinc had a significant reduction in the numbers of culturable aerosolized bacteria. For both Salmonella enterica and Listeria seeligeri there was a 70% reduction (p ≤ 0.0056 vs. control). On the other hand, in the absence of zinc there was a slight reduction in the activity of the essential oils; they reduced viable Salmonella enterica by 54% and Listeria seeligeri by 50% (≤ 0.0040 vs. control). The essential oil alone, without the gel formulation, also showed significant but again slightly reduced antimicrobial activity. This resulted in a 54% reduction in viable Salmonella enterica (p = 0.0005 vs. control) and a 30% reduction in Listeria seeligeri (p = 0.0335 vs. control).
Conclusion:
The naturally occurring essential oils vapours were able to substantially decrease the viable count of aerosolized Salmonella enterica and Listeria seeligeri. These antimicrobial agents hold the potential to mitigate aerosol transmission of microbes, making them a valuable tool in both the domestic and food industry settings.