In vitro antimicrobial properties of plant essential oils thymus vulgaris, cymbopogon citratus and laurus nobilis against five important foodborne pathogens Propriedades antibacterianas in vitro de óleos essenciais de thymus vulgaris, cymbopogon citratus e laurus nobilis contra cinco importantes bactérias patogênicas veiculadas por alimentosAlessandra Farias MILLEZI 1 *, Danila Soares CAIXETA 1 , Diogo Francisco ROSSONI 2 , Maria das Graças CARDOSO 3 , Roberta Hilsdorf PICCOLI 4 IntroductionThe essentials oils are products of the secondary plants' metabolism and several of them are used as seasonings and medicines. They can be defined as complex mixtures of volatile, lipophilic, odoriferous, and liquid substances (SIMÕES; SPITZER, 2004). The essential oils play an important role in plant protection such as antibacterial, antiviral, antifungal, insecticidal properties and also against herbivore attack. Currently, 3.000 essentials oils are known, 300 of which are commercially important in the pharmaceutical, agronomic, food, sanitation, cosmetics, and perfume industries (BAKKALI et al., 2008).The antimicrobial properties of condiment and medicinal plant essential oils have been stirring interest from the perspective of their making up an alternative to the use of chemical additives in foods. In recent years, it has been related that some essentials oils are capable of inhibiting bacteria of food origin and prolonging the shelf life of processed foods (KIM et al., 1995;SMITH-PALMER;STEWART;FYFE, 1998). Due to their hydrophobic characteristic, these compounds act over the lipids of the cell membrane modifying its structure and turning it more permeable, allowing the passage of ions and or other substances. ResumoDiversos óleos essenciais de plantas condimentares e medicinais possuem atividade antimicrobiana comprovada, sendo de grande interesse para a indústria de alimentos. Dessa forma, as Concentrações Mínimas Inibitórias (CMI) desses óleos para diversas bactérias devem ser determinadas. As CMI variam de acordo com o óleo utilizado, dos compostos majoritários e da fisiologia da bactéria em estudo. Na presente pesquisa, os óleos essenciais das plantas Thymus vulgaris (tomilho), Cymbopogon citratus (capim-limão) e Laurus nobilis (louro) foram quantificados quimicamente e determinou-se a CMI sobre as bactérias Staphylococcus aureus ATCC 25923, Escherichia. coli ATCC 25922, Listeria monocytogenes ATCC 19117, Salmonella entérica Enteritidis S64 e Pseudomonas aeruginosa ATCC 27853. O óleo essencial de C. citratus demonstrou atividade bacteriana em todas as concentrações testadas e sobre todas as bactérias, sendo seus constituintes majoritários o geranial e neral. O constituinte majoritário de T. vulgaris foi 1,8 cineol e do óleo de L. nobilis, que apresentou menor atividade antibacteriana, foi o linalool, seguido pelo 1,8 cineol. As bactérias Gram-negativas demostraram maior resistência perante o uso dos óleos essenciais testados neste estudo, E. coli foi a menos sensível, sendo inibida apenas pelos óleos de C. citratus...

This study demonstrates the possibility of using sanitizing detergents based on natural products for the elimination and/or reduction of Aeromonas hydrophila biofilm formed on stainless steel surfaces. The goal of this work was to determine the reduction effect of sanitizing detergents containing essential oils of Thymus vulgaris (thyme) and Cymbopogon citratus (lemongrass) on biofilm formed by A. hydrophila on AISI 304 stainless steel coupons, using UHT skimmed milk as substratum. There was adhesion and biofilm formation by A. hydrophila at 28 °C, presenting 7.60 log cfu.cm−2 after the fourth day of cultivation. There was no significant difference between the lemongrass treatment and that of the thyme oil (p < 0.05). However, both treatments significantly reduced the biofilm, differing significantly from the NaOH control (p > 0.05). The treatment with lemongrass solution reduced the biofilm by 4.51 log cfu cm−2 at 25 °C. The thyme detergent also reduced the number of cfu cm−2 by 3.84 log cycles at 25 °C. The use of the lemongrass and thyme solutions efficiently reduced the A. hydrophila biofilm.

INTRODUÇÃOOs óleos essenciais (OEs) são definidos como substâncias complexas voláteis, lipofílicas, geralmente odoríferas e líquidas, oriundas do metabolismo secundário de vegetais. Estes podem ser aplicados em vários segmentos, como antibacterianos, antivirais, antifúngicos, inseticidas e contra o ataque de herbívoros, bem como nos setores de higiene pessoal, perfumaria, cosmética, com um mercado mundial girando em torno de US$ 1,8 bilhão. A participação do Brasil corresponde a apenas 0,1% deste valor sendo 80% referente ao comércio de óleo de laranja (Simões & Spitzer, 2004;Costa, 2008).As propriedades antimicrobianas dos OEs de plantas condimentares e medicinais têm despertado interesse pela perspectiva de constituírem alternativa frente à utilização de aditivos químicos em alimentos. Nos últimos anos tem sido relatado que alguns OEs são capazes de inibir bactérias de origem alimentar e prolongar a vida de prateleira de alimentos processados (Kim et al., 1995; Smith-Palmer et al., 1998 Palavras-chave: antimicrobianos naturais, bactérias, óleos essenciais ABSTRACT: Chemical characterization and antibacterial activity of essential oils from medicinal and condiment plants against Staphylococcus aureus and Escherichia coli.Essential oils are plant secondary metabolites with different biological properties, such as activity against microorganisms, being of major interest to the food industry. The minimal inhibitory concentrations (MIC) of these oils for various bacteria should be determined. The MICvaries according to the oil used by the major compounds and phenotypic and genotypic characteristics of the bacteria. In this research, the essential oils of the plants Satureja montana L., Cymbopogon nardus L. and Citrus limonia Osbeck were chemically characterized and the MIC of the bacteria Staphylococcus aureusATCC 2592 and Escherichia coli ATCC 25922, determined. The MICfor all oils against E. coli was 1.5%, and S. aureus was sensitive to the concentration of 5.0% of S. montanaoil and tothe concentration of 1.5% of the essential oils of the other plants.Chemically, the major components ofthe S. montana, C. nardus and C.limonia Osbeck oils were respectively thymol, citronellal and limonene.

Essential oils are plant secondary metabolites commonly used in traditional medicine to treat infectious diseases. Along with their compounds, oils can contribute to development of new antimicrobial/antibiofilm products. Our study evaluated antibacterial activity of essential oils and their major compounds on Escherichia coli and Staphylococcus aureus planktonic cells and anti-biofilm activity. The effect of essential oils and their major compounds on biofilm and planktonic cells was assessed by quantifying the number of viable cells (CFU). Biomass quantification (absorbance = OD 570nm ) was also performed to evaluate anti-biofilm activity. Planktonic cells were more susceptible to the action of agents. Escherichia coli was reduced by 100 % with cinnamon and palmarosa oil. The treatment showed an interesting anti-biofilm activity, whereas green tea essential oil and its major compound, terpinen-4-ol, yielded less effective results. Reduction of viable cells in biofilm biomass was significant. Although our research is one of the first experiments in anti-biofilm activity of essential oils and their compounds against Escherichia coli and Staphylococcus aureus, pharmacological data confirm that the materials used in the trial do not pose health risk. Thus, essential oils and their compounds can be safely used in research to identify new antibacterial and anti-biofilm products against pathogenic bacteria.

Biofilms are responsible for most of the interference caused by microorganisms in food processing. The aim of this study was to evaluate the cinnamon (Cinnamomum zeylanicum) essential oil and eugenol sanitizer and anti-biofilm activity against biofilms. Concentrations used of essential oil were 0.0% (control) 0.12%; 0.48%; 0.96% and 1.92%; the amount of eugenol was 0.76%. Concentrations were determined from other published studies. Number of viable cells and quantification the bacterial biomass were determined. Anti-biofilm treatment was effective in preventing the formation of biofilms. The 1.92% concentration was the most satisfactorily with Escherichia coli reduction of 5.91log CFUcm-2 and Staphylococcus aureus reduction of 5.17log CFUcm-2 (P<0.05) biomass of the two bacteria. Sanitizing treatment was not effective in reducing biomass. Seen this, the cinnamon and eugenol essential oil may be promising alternatives for controlling biofilms.