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. 2014 May;116(5):1149-63.
doi: 10.1111/jam.12453. Epub 2014 Feb 12.

Antiviral Efficacy and Mechanisms of Action of Oregano Essential Oil and Its Primary Component Carvacrol Against Murine Norovirus

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Antiviral Efficacy and Mechanisms of Action of Oregano Essential Oil and Its Primary Component Carvacrol Against Murine Norovirus

D H Gilling et al. J Appl Microbiol. .
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Abstract

Aims: To investigate the antiviral efficacy of oregano oil and its primary active component, carvacrol, against the nonenveloped murine norovirus (MNV), a human norovirus surrogate.

Methods and results: Along with an observed loss in cell culture infectivity, the antiviral mechanisms of action were determined in side-by-side experiments including a cell-binding assay, an RNase I protection assay and transmission electron microscopy (TEM). Both antimicrobials produced statistically significant reductions (P ≤ 0·05) in virus infectivity within 15 min of exposure (c. 1·0-log10). Despite this, the MNV infectivity remained stable with increasing time exposure to oregano oil (1·07-log10 after 24 h), while carvacrol was far more effective, producing up to 3·87-log10 reductions within 1 h. Based on the RNase I protection assay, both antimicrobials appeared to act directly upon the virus capsid and subsequently the RNA. Under TEM, the capsids enlarged from ≤35 nm in diameter to up to 75 nm following treatment with oregano oil and up to 800 nm with carvacrol; with greater expansion, capsid disintegration could be observed. Virus adsorption to host cells did not appear to be affected by either antimicrobial.

Conclusions: Our results demonstrate that carvacrol is effective in inactivating MNV within 1 h of exposure by acting directly on the viral capsid and subsequently the RNA.

Significance and impact of the study: This study provides novel findings on the antiviral properties of oregano oil and carvacrol against MNV and demonstrates the potential of carvacrol as a natural food and surface (fomite) sanitizer to control human norovirus.

Keywords: human norovirus; mechanism of action; nonenveloped viruses; plant antimicrobials; sanitizer.

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