Essential oils as antimicrobial agents against bacteria Listeria monocytogenes

Abstract

Listeria monocytogenes is an important gram-positive foodborne pathogen which can cause the serious illness, listeriosis, which leads to a 30% rate of mortality among patients. This bacteria is often linked to ready-to-eat food because it is able to grow at refrigeration temperatures and many outbreaks are associated with the consumption of these products. With this in mind, the application of essential oils (EOs) to food products is a suitable strategy to control pathogens and to extend their shelf life by reducing microbial levels. The main objective of the present study was performed in order to evaluate the efficacy of EOs against L. monocytogenes. The EOs used in this study were caraway (Carum carvi), cinnamon (Cinnamomum zeylanicum), dill (Anethum graveolens), clove (Syzygium aromaticum), mentha (Menthae piperitae aetheroleum), red thyme (Thymus vulgaris), rosemary (Rosmarinus officinalis), common sage (Salvia officinalis), clary sage (Salvia sclarea) and summer savory (Satureja hortensis). The broth microdilution method was used to determine the minimum inhibitory concentrations (MICs) of plant essential oils (EOs). According to the MIC values, all essential oils were effective in the inhibition of L. monocytogenes strains, with MICs varying from 256 μg/ml to 4096 μg/ml. The results showed that cinnamon EO had the highest antimicrobial activity, while dill and mentha were the least effective against the L. monocytogenes strains. Hence, these findings open up new perspectives on the application of EOs as biopreservatives against food-borne pathogens.