FC 2007 Inhibitory effects of selected plant essential oils on the growth of four pathogenic bacteria: E. coli O157:H7, Salmonella Typhimurium, Staphylococcus aureus and Listeria monocytogenes Twenty eight essential oils were evaluated for their antibacterial properties, against four pathogenic bacteria (Escherichia coli O157:H7, Listeria monocytogenes 2812 1/2a, Salmonella Typhimurium SL 1344 and Staphylococcus aureus). Essential oils were introduced into Brain Heart Infusion agar (BHI) (15 ml) at a concentration of 0.003%, 0.006%, 0.013%, 0.025%, 0.05%, 0.1%, 0.2%, 0.4% and 0.8% (vol/vol) to determine the minimum inhibitory concentration (MIC) and the maximal tolerated concentration (MTC) for each pathogen evaluated. Results showed that the most active essential oils against bacteria tested were Corydothymus capitatus, Cinnamomum cassia, Origanum heracleoticum, Satureja montana, and Cinnamomum verum (bark). These showed a MIC ⩽ 0.05% (vol/vol) for all bacteria tested. For the MTC, with the exception of S. Typhimurium and L. monocytogenes where a MTC of 0.025% (vol/vol) was observed in presence of Cinnamomum verum and Cinnamomum cassia, respectively, a MTC ⩽ 0.013% (vol/vol) was observed for all other bacteria and the three other most active essential oils. Three oils (Satureja hortensis, Thymus vulgaris carvacroliferum, Origanum compactum) showed a MIC ⩽ 0.1% (vol/vol) for all bacteria tested. Seven oils (Thymus vulgaris thymoliferum, Thymus serpyllum, Thymus satureioides, Cymbopogon martinii, Pimenta dioica, Cinnamomum verum (leaf), Eugenia caryophyllus) showed a lower antimicrobial activity showing a MIC ⩽ 0.4% (vol/vol) against the four bacteria tested. Finally, 13 essential oils were less active showing a MIC value ⩾ 0.8% (vol/vol) against at least one bacterium. FEMS 2006 Susceptibility of methicillin-resistant staphylococci to oregano essential oil, carvacrol and thymol The aim of this study was to evaluate the susceptibility of methicillin-susceptible and methicillin-resistant staphylococci (MSS, MRS) to oregano essential oil, carvacrol and thymol. The commercial aerial parts of Origanum vulgare L. were hydrodistilled and the essential oil analysed by gas- chromatography/electron impact mass spectrometry. The inhibition efficacy of this essence and its major components was assayed against 26 MSS and 21 MRS, using an agar dilution method. The methicillin resistance was thoroughly typed by Epsilometer test (E-test), polymerase chain reaction for mecA gene detection and PBP2′ latex agglutination test. The results clearly demonstrated that the comparison between the susceptibility of MSS and MRS to oregano oil, carvacrol and thymol showed no significant differences (Fisher's exact test, P>0.05). The best minimum inhibitory concentration values were reported for carvacrol (0.015–0.03%, v/v) followed by thymol (0.03–0.06%, v/v) and oregano oil (0.06–0.125%, v/v). Article first published online: 9 JAN 2006 DOI: 10.1016/S0378-1097(03)00890-5 JAFC 2004 Chemical Compositions and Antibacterial Effects of Essential Oils of Turkish Oregano (Origanum minutiflorum), Bay Laurel (Laurus nobilis), Spanish Lavender (Lavandula stoechas L.), and Fennel (Foeniculum vulgare) on Common Foodborne Pathogens Chemical compositions and inhibitory effects of essential oils of Turkish oregano (Origanum minutiflorum O. Schwarz & P. H. Davis), bay laurel (Laurus nobilis L.), Spanish lavender (Lavandula stoechas subsp. stoechas L.), and fennel (Foeniculum vulgare Mill.) on Escherichia coli O157:H7, Listeria monocytogenes, Salmonella typhimurium, and Staphylococcus aureus were determined. After the essential oils were applied on the foodborne pathogens at doses of 0 (control), 5, 10, 20, 30, 40, 50, and 80 μL/mL, the resultant numbers of cells surviving were counted. Results revealed that all essential oils exhibited a very strong antibacterial activity against the tested bacteria (P < 0.05). Gas chromatography−mass spectrophotometry analyses revealed that carvacrol (68.23%), 1,8-cineole (60.72%), fenchone (55.79%), and trans-anethole (85.63%) were the predominant constituents in Turkish oregano, bay laurel, Spanish lavender, and fennel essential oils, respectively. JAM 2001 A study of the minimum inhibitory concentration and mode of action of oregano essential oil, thymol and carvacrol numerous studies in broth model systems, as well as in real foods, have revealed the bacteriostatic or bactericidal activity of this essential oil on pathogens such as Staph. aureus, Salmonella typhimurium, Escherichia coli, Ps. aeruginosa, Bacillus subtilis, spoilage bacteria Brochothrix thermosphacta, P. fluorescens, Serratia liquefaciens, Lactobacillus carvatus, Lact. sake and moulds Rhizobium leguminosarum, Aspergillus niger, Asp. flavus, Asp. ochraceus, Fusarium oxysporum and Penicillium spp. in broth (Conner and Beuchat 1984; Galli et al. 1985; Paster et al. 1990, 1995; Daouk et al. 1995; Sivropoulou et al. 1996; Quattara et al. 1997; Manou et al. 1998), as well as in real foods (Tassou et al. 1996; Koutsoumanis et al. 1999; Skandamis and Nychas 2000; Tsigarida et al. 2000). JAM 2006 Effects of oregano, carvacrol and thymol on Staphylococcus aureus and Staphylococcus epidermidis biofilms The aim of this study was to evaluate the effect of oregano essential oil, carvacrol and thymol on biofilm-grown Staphylococcus aureus and Staphylococcus epidermidis strains, as well as the effects of the oils on biofilm formation. For most of the S. aureus (n=6) and S. epidermidis (n=6) strains tested, the biofilm inhibitory concentration (0.125–0.500 %, v/v, for oregano, and 0.031–0.125 %, v/v, for carvacrol and thymol) and biofilm eradication concentration (0.25–1.0 %, v/v, for oregano and 0.125–0.500 %, v/v, for carvacrol and thymol) values were twofold or fourfold greater than the concentration required to inhibit planktonic growth. Subinhibitory concentrations of the oils attenuated biofilm formation of S. aureus and S. epidermidis strains on polystyrene microtitre plates. JDD 2010 Development of an oregano-based ointment with anti-microbial activity including activity against methicillin-resistant Staphlococcus aureus. Increasing antibiotic resistance has prompted a search for new compounds with anti-microbial activity. In the authors' previous study, oregano extract was identified as one of the most potent anti-microbial compounds. The disk diffusion method was employed to assess the degree of inhibition against various microorganisms, and the bacteriostatic or bactericidal mechanism of action. Disk diffusion studies showed that oregano was found to be bacteriostatic for Staphylococcus aureus (S. aureus) and methicillin-resistant S. aureus, (MRSA) but bacteriocidal for seven other microorganisms. Pseudomonas aeruginosa could not be inhibited by oregano. An ointment consisting of 1-10% oregano could inhibit most organisms except for Proteus mirabilis and Proteus vulgaris, which required 20% and Pseudomonas which could not be inhibited even at the highest concentration of 80%. Oregano extracts can be formulated into an ointment that shows broad antimicrobial activity. Additional testing to assess tissue toxicity and other adverse reactions would be needed prior to human testing. JFAE 2010 The antibacterial activity of essential oil of oregano (Origanum vulgare L.) Antibacterial activities of the essential oil of oregano (Origanum vulgare L.) and ampicillin on Escherichia coli RSKK 340, Klebsiella pneumoniae RSKK 06017, Pseudomonas aeruginosa RSKK 06021, Salmonella enteritidis RSKK 96046, Streptococcus pyogones RSKK 413/214, Bacillus cereus RSKK 1122, Staphylococcus aureus RSKK 96090 and methicilline-resistant Staphylococcus aureus (MRSA) were determined. The minimum inhibitory concentration (MIC) for oregano oil against various bacteria varied: while M.luteus (16 µg/ml) and B.cereus (32 µg/ml) were susceptible to oregano oil, the others exhibited partly resistance. Except MRSA S. aureus (250 µg/ml), ampicillin had more effect on K. pneumoniae (128 µg/ml) andC. albicans (128 µg/ml) than oregano oil, but very low concentrations of the essential oil were sufficient to prevent microbial growth. Of the bacteria tested, Micrococcus luteus and Bacillus cereus proved to be most susceptible to oregano oil. Oregano oil possessed strong antimicrobial activity compared with the antibiotic. Gram-positive bacteria were more sensitive to the antimicrobial agent in spice than Gram-negative ones.

JFP 2001 Antimicrobial Activity of Essential Oils from Plants against Selected Pathogenic and Saprophytic Microorganisms Authors: Elgayyar, M.; Draughon, F. A.; Golden, D. A.; Mount, J. R. Source: Journal of Food Protection, Volume 64, Number 7, 1 July 2001 , pp. 1019-1024(6) Publisher: International Association for Food Protection The beneficial health effects of extracts from many types of plants that are used as seasoning agents in foods and beverages have been claimed for centuries. The purpose of this study was to examine the effectiveness of selected herb and spice essential oils for control of growth and survival of microorganisms. Inhibition of growth was tested by the paper disc agar diffusion method. Antibiotic susceptibility discs were used as control. Minimum lethal concentration (MLC) was determined by the tube dilution method. Essential oils from anise, angelica, basil, carrot, celery, cardamom, coriander, dill weed, fennel, oregano, parsley, and rosemary were evaluated. Inhibition ranged from complete with oregano to no inhibition with carrot oil for each of the test strains that included: Listeria monocytogenes, Staphylococcus aureus, Escherichia coli O:157:H7, Yersinia enterocolitica, Pseudomonas aeruginosa, Lactobacillus plantarum, Aspergillus niger, Geotrichum, and Rhodotorula. Oregano essential oil showed the greatest inhibition (zone, ≥70 to 80 mm) (MLC, inhibitory (MLC, 25 to 50 ppm) to E. coli O:157:H7 and to the other bacteria and fungi tested. Anise oil was not particularly inhibitory to bacteria (inhibition zone, 25 mm); however, anise oil was highly inhibitory to molds. Because some of the herbal and spice essential oils are highly inhibitory to selected pathogenic and spoilage microorganisms, they may provide alternatives and supplements to conventional antimicrobial additives in foods. 8 ppm). Coriander and basil were also highly... JIMM 2009 Investigation of functional and morphological changes in Pseudomonas aeruginosa and Staphylococcus aureus cells induced by Origanum compactum essential oil The damage induced by O. compactum essential oil on these two strains has been studied using different techniques: plate count, potassium leakage, flow cytometry (FC) and transmission electron microscopy (TEM). The results showed that oil treatment led to reduction of cells viability and dissipated potassium ion gradients. Flow cytometric analysis showed that oil treatment promoted the accumulation of bis-oxonol and the membrane-impermeable nucleic acid stain propidium iodide (PI), indicating the loss of membrane potential and permeability. The ability to reduce 5-cyano-2,3-ditolyl tetrazolium chloride was inhibited. Unlike in Ps. aeruginosa, membrane potential and membrane permeability in Staph. aureus cells were affected by oil concentration and contact time. Finally, TEM showed various structural effects. Mesosome-like structures were seen in oil-treated Staph. aureus cells whereas in Ps. aeruginosa, coagulated cytoplasmic material and liberation of membrane vesicles were observed, and intracellular material was seen in the surrounding environment. Both FC and TEM revealed that the effects in Ps. aeruginosa were greater than in Staph. aureus. JMM 2009 In vitro activity of carvacrol against staphylococcal preformed biofilm by liquid and vapour contact Carvacrol is an important component of essential oils and recently has attracted much attention as a result of its biological properties, such as a wide spectrum of antimicrobial activity. The aim of this study was to evaluate the effect of carvacrol in liquid and vapour phase on preformed biofilms of Staphylococcus aureus and Staphylococcus epidermidis by determining biofilm biomass and cultivable cell numbers, and by using epifluorescence and scanning electron microscopy. Carvacrol was able to reduce biofilm biomass and cell viability more effectively when used with liquid contact rather than with vapour phase. The efficacy of treatment with carvacrol vapour was found to be dependent on exposure time. The predominance of red fluorescence using a LIVE/DEAD BacLight Viability kit (Molecular Probes) and the partially destroyed biofilm architecture as determined by microscopy in treated samples provided evidence for the efficacy of carvacrol. The findings of this investigation suggest a potential application for carvacrol in the inactivation of staphylococcal biofilms. LIAM 2008 Inhibitory effect of oregano and thyme essential oils on moulds and foodborne bacteria The essential oil of oregano (‘origanum oil’; thymol type oil from Origanum vulgare) inhibited completely the mycelial growth of Aspergillus niger and A. flaous at 400 μg/ml, while A. ochraceus was inhibited at 600 μg/ml. At 700 μg/ml, thyme oil inhibited the mycelial growth of A. flavus and A. niger but not that of A. ochraceus. Fungal spore germination was inhibited by 600 μg/ml of origanum oil and (with the exception of A. ochraceus) by 700 μg/ml of thyme oil. Under aerobic conditions, the essential oils of oregano (250 μg/ml) and thyme (350 μg/ml) inhibited to some extent the growth of Staphylococcus aureus and Salmonella typhimurium. Pseudomonas aeruginosa was not affected by either oregano or thyme oil at concentrations up to 500 μg/ml. The origanum oil was very effective against Campylohacter jejuni and Clostridiurn sporogenes and thyme oil was very effective against C. jejuni. The antagonistic effect of the two oils on Staph. aureus and Salm. typhimuriutn was greatly enhanced when those organisms were incubated in atmospheres of low oxygen tensions.#956;g/ml. At 700 LWT 2003 Sensitivity of four pathogenic bacteria to Turkish thyme and oregano hydrosols The two thyme (Thymus vulgaris L. and Thymus serpyllum L.) and three oregano (Origanum vulgare L., Origanum onites L. and Origanum majorana L.) hydrosols, widely used in food products and as drinks, were tested for their inhibitory effects against four pathogenic bacteria (Escherichia coli ATCC 25922, E. coli O157:H7 ATCC 33150, Staphylococcus aureus ATCC 2392 and Yersinia enterocolitica ATCC 1501). Two principles were used in determining the antibacterial effects of spice hydrosols: inhibition zones were determined by paper disc diffusion method, and the bacteriostatic effects, bactericidal effects and the growth inhibition levels were studied as colony forming units (cfu) in broth cultures. All tested bacteria were inhibited by all of the spice hydrosols using paper disc diffusion method. According to serial dilution method, while all spice hydrosols at 10 and 25 mL/100 mL concentrations had generally bacteriostatic activities, the same hydrosols appeared to have bactericidal effects at concentrations above 50 mL/100 mL. The most sensitive of the bacteria against the spice hydrosols was S. aureus. In addition, the most inhibitive of the spice hydrosols on the four pathogenic bacteria were O. onites L. and O. majorana L. WJMB 2000 Ecophysiological attributes of Salmonella typhimurium in liquid culture and within a gelatin gel with or without the addition of oregano essential oil The growth of Salmonella typhimurium in liquid culture and in a gel matrix system at two pH values (5.0 and 7.0) with (0.03% w/v) or without oregano essential oil was studied. It was shown that the type of growth media (liquid or gel) influenced significantly both the type of end-product formation and growth of bacteria as well as the inhibitory efficacy of the essential oil. The oil inhibited S. typhimurium more strongly in the liquid medium than in the gelatin matrix. In particular, the addition of essential oil in gelatin matrix delayed the initiation of growth and caused a slight suppression of the maximum population level, while in liquid culture, growth was prevented completely in identical conditions. Structure also was found to affect the rate of consumption of glucose and the rate of production of end products. Formic and acetic acids were produced in both systems, while an unidentified peak was formed only in broth samples. telegraph 2008 carvacrol, in oregano, is a more effective antimicrobial agent than 18 pharmaceutical drugs it was compared against. Scientists have discovered that the herb, commonly used in cooking, could eradicate the deadly infection from hospital wards. A team at the University of the West of England in Bristol, working with partners in India, found that tiny quantities of carvacrol, a naturally occurring compound in oregano, is a more effective antimicrobial agent than 18 pharmaceutical drugs it was compared against. The discovery could lead to a new defence in the fight against hospital infection. Carvacrol has been found to contain potent anti-fungal and antibacterial properties with a range of medicinal uses. It can sterilise septic water, kill giardia, treat fungal infections such as candida and rivals pharmaceutical antibiotics such as streptomycin and penicillin in its ability to eliminate microbes.