Essential oils as antibacterial agents against food-borne pathogens: Are they really as useful as they are claimed to be?

Most studies evaluating the use of essential oils (EO) as antibacterial agents focus mainly on minimal inhibitory concentrations (MIC) rather than minimal bactericidal concentrations (MBC). In this work, we compared MICs and MBCs of EO from condiment plants commonly used in Mediterranean Europe, namely Origanum vulgare, Salvia lavandulaefolia, Salvia officinalis, Salvia sclarea and Rosmarinus officinalis, aiming to evaluate their application as disinfecting agents in minimally processed produce. Outbreaks-related pathogens such as Listeria monocytogenes, Pseudomonas aeruginosa and Yarrowia lipolytica were used. Results showed that all EO were able to reduce bacterial growth in all bacterial strains tested, particularly O. vulgare. However, fewer EO exhibited bactericidal activities, and were only effective against one or two bacterial strains, hence eliminating the possibility to use them as broad range disinfectants. Furthermore, the necessary concentrations were too high for food application. Hence, our work suggests the need to evaluate MBC rather than MIC and questions EO usefulness in controlling undesired microorganisms. Overall, and despite the large volume of data published on EO, results obtained were not very encouraging for a realistic application on produce and question the viability of EOs as disinfecting agents in food.

Molecular typing of Salmonella from Sergipe, Northeastern Brazil, showing the epidemiological relationship between poultry and human infection.

Randomly amplified polymorphic DNA (RAPD) has been widely used for epidemiological and phylogenetic purposes ow-ing to its rapidity and efficiency. The aim of this study was to perform genome typing of Salmonella samples isolated from different sources by RAPD profiling. Thirty-three Salmonella samples from the bacterial collection of the Laboratório de Virologia Comparada, Departamento de Morfologia, Universidade Federal de Sergipe, Brazil, and two standard samples were used. RAPD profiling was conducted using six primers of the Ready-To-Go RAPD system. The amplified products were electro-phoresed on 5% polyacrylamide gel and silver-stained. RAPD analysis resulted in reproducible and stable banding patterns and showed high genetic diversity among the isolated strains. The Primer P1-generated dendrogram showed an epidemiologic relationship between the human and poultry isolated samples, highlighting the usefulness of RAPD for molecular typing and epidemiological studies.